View source for Astronomy:New Horizons

{{Short description|NASA probe that visited Pluto and Kuiper belt object 486958 Arrokoth}}
{{Italic title}}
{{Infobox spaceflight
| name = ''New Horizons''
| image = New Horizons Transparent.png
| image_caption = ''New Horizons'' space probe
| image_size = 300px
| insignia = New Horizons - Logo2 big.png
| insignia_size = 150x150px
| mission_type = [[Engineering:Flyby (spaceflight)|Flyby]] <br />([[Astronomy:132524 APL|132524 APL]]{{dot}} [[Astronomy:Jupiter|Jupiter]]{{dot}}[[Astronomy:Pluto|Pluto]]{{dot}}[[Astronomy:486958 Arrokoth|486958 Arrokoth]])
| operator = [[Organization:NASA|NASA]]
| COSPAR_ID = 2006-001A
| SATCAT = 28928
| website = {{URL|http://pluto.jhuapl.edu}} <br /> {{URL|1=https://www.nasa.gov/newhorizons |2=nasa.gov/newhorizons}}
| mission_duration = Primary mission: 9.5&nbsp;years <br /> Elapsed: {{time interval|19 January 2006 19:00|show=ymd|sep=,}}
| manufacturer = [[Organization:Applied Physics Laboratory|APL]]{{\}}[[Organization:Southwest Research Institute|SwRI]]
| launch_mass = {{cvt|478|kg|lb}}<ref>{{cite web|url=https://solarsystem.nasa.gov/missions/new-horizons/in-depth/ |title=New Horizons |publisher=NASA's Solar System Exploration website |access-date=December 1, 2022}}</ref>
| dry_mass = {{cvt|401|kg|lb}}
| payload_mass = {{cvt|30.4|kg|lb}}
| dimensions = {{cvt|2.2|xx|2.1|xx|2.7|m|ft}}
| power = 245 watts
| launch_date = {{start-date|January 19, 2006, 19:00:00.221}}&nbsp;UTC<ref name="eelv-history">{{cite report |url=http://afspacemuseum.org/library/histories/EELV.pdf |title=Evolved Expendable Launch Operations at Cape Canaveral, 2002–2009 |publisher=Air Force Space & Missile Museum |agency=45th Space Wing History Office |first=Mark C. |last=Cleary |page=30 |date=August 2010 |access-date=January 3, 2020 |archive-date=January 3, 2020 |archive-url=https://web.archive.org/web/20200103210054/http://afspacemuseum.org/library/histories/EELV.pdf |url-status=dead }}</ref>
| launch_rocket = [[Engineering:Atlas V|Atlas V]] (551) AV-010<ref name="eelv-history" /> + [[Astronomy:Star 48|Star 48]]B 3rd stage
| launch_site = {{wipe|Cape Canaveral Air Force Station}} SLC-41
| launch_contractor = [[Company:International Launch Services|International Launch Services]]<ref>{{cite web |url=http://www.ilslaunch.com/atlas-launch-archives |title=Atlas Launch Archives |publisher=International Launch Services |access-date=April 21, 2018 |archive-date=April 22, 2018 |archive-url=https://web.archive.org/web/20180422132703/http://www.ilslaunch.com/atlas-launch-archives |url-status=live }}</ref>
| disposal_type = <!--deorbited, decommissioned, placed in a graveyard orbit, etc-->
| deactivated = <!--when craft was decommissioned-->
| last_contact = <!--when last signal received if not decommissioned-->
| orbit_eccentricity = 1.41905
| orbit_inclination = 2.23014°
| orbit_epoch = January 1, 2017 ([[Astronomy:Julian day|JD]] 2457754.5)<ref>{{cite web |url=http://ssd.jpl.nasa.gov/horizons.cgi |title=HORIZONS Web-Interface |publisher=NASA/JPL |access-date=July 25, 2016 |archive-date=October 7, 2012 |archive-url=https://web.archive.org/web/20121007034731/http://ssd.jpl.nasa.gov/horizons.cgi |url-status=live }} To find results, change Target Body to "New Horizons", Center to "@Sun", and Time Span to include "2017-01-01".</ref>
| interplanetary = {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Astronomy:132524 APL|132524 APL]]
   |note                = incidental
   |distance            = {{cvt|101,867|km}}
   |arrival_date        = June 13, 2006, 04:05&nbsp;UTC
 }}
 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Astronomy:Jupiter|Jupiter]]
   |note                = gravity assist
   |distance            = {{cvt|2,300,000|km}}
   |arrival_date        = February 28, 2007, 05:43:40&nbsp;UTC
 }}
 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Astronomy:Pluto|Pluto]]
   |distance            = {{cvt|12,500|km}}
   |arrival_date        = July 14, 2015, 11:49:57&nbsp;UTC
 }}
 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Astronomy:486958 Arrokoth|486958 Arrokoth]]
   |arrival_date        = January 1, 2019, 05:33:00&nbsp;UTC
   |distance            = {{cvt|3,500|km}}
 }}
| instruments_list = {{Infobox spaceflight/Instruments
  |acronym1 = Alice  |name1 = Ultraviolet Imaging Spectrometer
  |acronym2 = LORRI  |name2 = Long-Range Reconnaissance Imager
  |acronym3 = SWAP   |name3 = Solar Wind Around Pluto
  |acronym4 = PEPSSI |name4 = Pluto Energetic Particle Spectrometer Science Investigation
  |acronym5 = REX    |name5 = Radio Science Experiment
  |acronym6 = Ralph  |name6 = Ralph Telescope
  |acronym7 = SDC    |name7 = Venetia Burney Student Dust Counter
 }}
| programme = '''[[Astronomy:New Frontiers program|New Frontiers program]]'''
| previous_mission = 
| next_mission = ''[[Engineering:Juno (spacecraft)|Juno]]''
}}
[[File:New Horizons on work stand.jpg|thumb|New Horizons before launch]]

'''''New Horizons''''' is an [[Astronomy:Interplanetary spaceflight|interplanetary space probe]] launched as a part of [[Organization:NASA|NASA]]'s [[Astronomy:New Frontiers program|New Frontiers program]].<ref name="NYT-20150718">{{cite news |last=Chang |first=Kenneth |title=The Long, Strange Trip to Pluto, and How NASA Nearly Missed It |url=https://www.nytimes.com/2015/07/19/us/the-long-strange-trip-to-pluto-and-how-nasa-nearly-missed-it.html |date=July 18, 2015 |work={{wipe|The New York Times}} |access-date=July 19, 2015 |archive-date=September 20, 2019 |archive-url=https://web.archive.org/web/20190920084409/https://www.nytimes.com/2015/07/19/us/the-long-strange-trip-to-pluto-and-how-nasa-nearly-missed-it.html |url-status=live }}</ref> Engineered by the Johns Hopkins University [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] (APL) and the [[Organization:Southwest Research Institute|Southwest Research Institute]] (SwRI), with a team led by [[Biography:Alan Stern|Alan Stern]],<ref name="tri">{{cite podcast |url=https://twit.tv/shows/triangulation/episodes/215 |title=Alan Stern: principal investigator for New Horizons |website=TWiT.tv |host=Leo Laporte |date=August 31, 2015 |access-date=September 1, 2015}}</ref> the spacecraft was launched in 2006 with the primary mission to perform a [[Engineering:Planetary flyby|flyby]] study of the [[Astronomy:Pluto|Pluto]] system in 2015, and a secondary mission to fly by and study one or more other [[Astronomy:Kuiper belt|Kuiper belt]] objects (KBOs) in the decade to follow, which became a mission to [[Astronomy:486958 Arrokoth|486958 Arrokoth]]. It is the fifth space probe to achieve the [[Astronomy:Escape velocity|escape velocity]] needed to leave the [[Astronomy:Solar System|Solar System]].

On January 19, 2006, ''New Horizons'' was launched from {{wipe|Cape Canaveral Air Force Station}} by an [[Engineering:Atlas V|Atlas V]] [[Engineering:Rocket|rocket]] directly into an Earth-and-solar [[Astronomy:Escape velocity|escape trajectory]] with a speed of about {{cvt|16.26|km/s|mi/s km/h mph|sp=us}}. It was the fastest (average speed with respect to Earth) human-made object ever launched from Earth.<ref name="APL-20070116"/><ref name="sciam20130225"/><ref name="ionine20150609"/><ref name="ET-20171213">{{cite web | url=https://www.extremetech.com/extreme/260472-next-target-new-horizons-probe-may-tiny-moonlet | title=New Horizons Space Probe Target May Have its Own Tiny Moonlet – ExtremeTech |date=December 13, 2017 |last=Whitwam |first=Ryan |access-date=January 24, 2019 |publisher=Ziff Davis}}</ref> It is not the fastest speed recorded for a spacecraft, which, as of 2023, is that of the [[Astronomy:Parker Solar Probe|Parker Solar Probe]]. After a brief encounter with [[Astronomy:Asteroid|asteroid]] [[Astronomy:132524 APL|132524 APL]], ''New Horizons'' proceeded to [[Astronomy:Jupiter|Jupiter]], making its closest approach on February 28, 2007, at a distance of {{convert|2.3|e6km|abbr=off|sp=us}}. The Jupiter flyby provided a [[Astronomy:Gravity assist|gravity assist]] that increased ''New Horizons''{{'}} speed; the flyby also enabled a general test of ''New Horizons''{{'}} scientific capabilities, returning data about [[Astronomy:Atmosphere of Jupiter|the planet's atmosphere]], [[Astronomy:Moons of Jupiter|moons]], and [[Astronomy:Magnetosphere of Jupiter|magnetosphere]].

Most of the post-Jupiter voyage was spent in hibernation mode to preserve onboard systems, except for brief annual checkouts.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/index.php |title=New Horizons: NASA's Mission to Pluto |work=NASA |access-date=April 15, 2015}}</ref> On December 6, 2014, ''New Horizons'' was brought back online for the Pluto encounter, and instrument check-out began.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20141206 |title=New Horizons – News |work=Johns Hopkins Applied Physics Laboratory |date=December 6, 2014 |access-date=April 15, 2015}}</ref> On January 15, 2015, the spacecraft began its approach phase to Pluto.

On July 14, 2015, at 11:49&nbsp;[[UTC]], it flew {{cvt|12500|km}} above the surface of Pluto,<ref name="NYT-20150714-kc">{{cite news |last=Chang |first=Kenneth |title=NASA's New Horizons Spacecraft Completes Flyby of Pluto |url=https://www.nytimes.com/2015/07/15/science/space/nasa-new-horizons-spacecraft-reaches-pluto.html |date=July 14, 2015 |work={{wipe|The New York Times}} |access-date=July 14, 2015 |archive-date=January 18, 2018 |archive-url=https://web.archive.org/web/20180118163357/https://www.nytimes.com/2015/07/15/science/space/nasa-new-horizons-spacecraft-reaches-pluto.html |url-status=live }}</ref><ref name="AP-20150714">{{cite news |last=Dunn |first=Marcia |title=Pluto close-up: Spacecraft makes flyby of icy, mystery world |url=http://apnews.excite.com/article/20150714/us-sci--pluto-1a20f848e7.html |date=July 14, 2015 |work=[[Company:Excite (web portal)|Excite]] |agency=Associated Press (AP) |access-date=July 14, 2015 |archive-date=July 16, 2015 |archive-url=https://web.archive.org/web/20150716165559/http://apnews.excite.com/article/20150714/us-sci--pluto-1a20f848e7.html |url-status=live }}</ref> which at the time was 34 AU from the Sun,<ref>{{cite web|title=New Horizons|url=https://solarsystem.nasa.gov/missions/new-horizons/in-depth/|website=NASA|access-date=March 10, 2023}}</ref> making it the first spacecraft to explore the dwarf planet.<ref name="NASA-20150714-kn">{{cite web |last1=Brown |first1=Dwayne |last2=Cantillo |first2=Laurie |last3=Buckley |first3=Mike |last4=Stotoff |first4=Maria |title=15-149 NASA's Three-Billion-Mile Journey to Pluto Reaches Historic Encounter |url=http://www.nasa.gov/press-release/nasas-three-billion-mile-journey-to-pluto-reaches-historic-encounter |date=July 14, 2015 |work=[[Organization:NASA|NASA]] |access-date=July 14, 2015 |archive-date=June 17, 2019 |archive-url=https://web.archive.org/web/20190617084402/https://www.nasa.gov/press-release/nasas-three-billion-mile-journey-to-pluto-reaches-historic-encounter/ |url-status=live }}</ref> In August 2016, ''New Horizons'' was reported to have traveled at speeds of more than {{convert|84,000|km/h|mph|abbr=on}}.<ref name="SPC-20160824">{{cite news |last=Cofield |first=Calia |title=How We Could Visit the Possibly Earth-Like Planet Proxima b |url=https://www.space.com/33844-proxima-b-exoplanet-interstellar-mission.html |date=August 24, 2016 |work=Space.com |access-date=October 1, 2019 }}</ref> On October 25, 2016, at 21:48&nbsp;UTC, the last recorded data from the Pluto flyby was received from ''New Horizons''.<ref name="NYT-20161028">{{cite news |url=https://www.nytimes.com/2016/10/29/science/pluto-nasa-new-horizons.html |title=No More Data From Pluto |work={{wipe|The New York Times}} |last=Chang |first=Kenneth |date=October 28, 2016 |access-date=October 28, 2016 |archive-date=March 29, 2019 |archive-url=https://web.archive.org/web/20190329002642/https://www.nytimes.com/2016/10/29/science/pluto-nasa-new-horizons.html |url-status=live }}</ref> Having completed its flyby of Pluto,<ref name="NYT-20151211-rj">{{cite news |last=Jayawardhana |first=Ray |title=Give It Up for Pluto |url=https://www.nytimes.com/2015/12/13/opinion/give-it-up-for-pluto.html |date=December 11, 2015 |work={{wipe|The New York Times}} |access-date=December 11, 2015 |archive-date=July 10, 2018 |archive-url=https://web.archive.org/web/20180710011707/https://www.nytimes.com/2015/12/13/opinion/give-it-up-for-pluto.html |url-status=live }}</ref> ''New Horizons'' then maneuvered for a flyby of Kuiper belt object [[Astronomy:486958 Arrokoth|486958 Arrokoth]] (then nicknamed ''Ultima Thule''),<ref name="NASA-20150828-tt">{{cite web |last=Talbert |first=Tricia |title=NASA's New Horizons Team Selects Potential Kuiper Belt Flyby Target |url=http://www.nasa.gov/feature/nasa-s-new-horizons-team-selects-potential-kuiper-belt-flyby-target |date=August 28, 2015 |work=[[Organization:NASA|NASA]] |access-date=September 4, 2015 |archive-date=September 26, 2015 |archive-url=https://web.archive.org/web/20150926211423/https://www.nasa.gov/feature/nasa-s-new-horizons-team-selects-potential-kuiper-belt-flyby-target/ |url-status=live }}</ref><ref name="SP-20150828">{{cite web |last1=Cofield |first1=Calla |title=Beyond Pluto: 2nd Target Chosen for New Horizons Probe |url=http://www.space.com/30415-new-horizons-pluto-mission-next-target.html |date=August 28, 2015 |work=Space.com |access-date=August 30, 2015 |archive-date=July 12, 2019 |archive-url=https://web.archive.org/web/20190712201151/https://www.space.com/30415-new-horizons-pluto-mission-next-target.html |url-status=live }}</ref><ref name="AP-20151022">{{cite news |last=Dunn |first=Marcia |title=NASA's New Horizons on new post-Pluto mission |url=http://apnews.excite.com/article/20151022/us-sci--pluto-next_stop-3b1bf3f8fc.html |date=October 22, 2015 |agency=Associated Press |access-date=October 25, 2015 |archive-date=October 28, 2015 |archive-url=https://web.archive.org/web/20151028230840/http://apnews.excite.com/article/20151022/us-sci--pluto-next_stop-3b1bf3f8fc.html |url-status=live }}</ref> which occurred on January 1, 2019,<ref name="NYT-20190210">{{cite news |last=Corum |first=Jomathan |title=New Horizons Glimpses the Flattened Shape of Ultima Thule – NASA's New Horizons spacecraft flew past the most distant object ever visited: a tiny fragment of the early solar system known as 2014 MU69 and nicknamed Ultima Thule. – Interactive |url=https://www.nytimes.com/interactive/2018/12/31/science/new-horizons-ultima-thule-flyby.html |date=10 February 2019 |work={{wipe|The New York Times}} |access-date=11 February 2019 }}</ref><ref name="NYT-20181231-kc">{{cite news |last=Chang |first=Kenneth |title=New Horizons Spacecraft Completes Flyby of Ultima Thule, the Most Distant Object Ever Visited |url=https://www.nytimes.com/2018/12/31/science/new-horizons-ultima-thule.html |date=December 31, 2018 |work={{wipe|The New York Times}} |access-date=January 1, 2019 |archive-date=November 19, 2019 |archive-url=https://web.archive.org/web/20191119160017/https://www.nytimes.com/2018/12/31/science/new-horizons-ultima-thule.html |url-status=live }}</ref> when it was {{Convert|43.4|AU|e9km e9mi|lk=on|abbr=unit}} from the [[Astronomy:Sun|Sun]].<ref name="NASA-20150828-tt" /><ref name="SP-20150828" /> In August 2018, NASA cited results by ''Alice'' on ''New Horizons'' to confirm the existence of a "hydrogen wall" at the [[Astronomy:Solar System#Farthest regions|outer edges of the Solar System]]. This "wall" was first detected in 1992 by the two [[Astronomy:Voyager program|Voyager spacecraft]].<ref name="GRL-20180807">{{cite journal |author=Gladstone, G. Randall |display-authors=0 |title=The Lyman‐α Sky Background as Observed by New Horizons |date=August 7, 2018 |journal=[[Earth:Geophysical Research Letters|Geophysical Research Letters]] |volume=45 |issue=16 |page=8022 |doi=10.1029/2018GL078808 |arxiv=1808.00400 
|bibcode=2018GeoRL..45.8022G |s2cid=119395450 }}</ref><ref name="LS-20180809">{{cite web |last=Letzter |first=Rafi |title=NASA Spotted a Vast, Glowing 'Hydrogen Wall' at the Edge of Our Solar System |url=https://www.livescience.com/63297-hydrogen-wall-glowing-interstellar-space.html |date=August 9, 2018 |work=Live Science |access-date=August 10, 2018 |archive-date=April 13, 2020 |archive-url=https://web.archive.org/web/20200413080736/https://www.livescience.com/63297-hydrogen-wall-glowing-interstellar-space.html |url-status=live }}</ref> NASA has announced it is to extend operations for New Horizons until the spacecraft exits the Kuiper Belt, which is expected to occur between 2028 and 2029.<ref>{{Cite web |last=O'Callaghan |first=Jonathan |title=Beyond Pluto, New Horizons Gets a Reprieve from NASA |url=https://www.scientificamerican.com/article/beyond-pluto-new-horizons-gets-a-reprieve-from-nasa/ |access-date=2024-01-07 |website=Scientific American |language=en}}</ref> 
{{Clear|left}}

== History ==
{{Main|Astronomy:Exploration of Pluto}}
[[File:New horizons (NASA).jpg|thumb|right|Early concept art of the ''New Horizons'' spacecraft. The mission, led by the Applied Physics Laboratory and Alan Stern, eventually became the first mission to Pluto.]]

In August 1992, [[Organization:Jet Propulsion Laboratory|JPL]] scientist Robert Staehle called Pluto discoverer [[Biography:Clyde Tombaugh|Clyde Tombaugh]], requesting permission to visit his planet. "I told him he was welcome to it," Tombaugh later remembered, "though he's got to go one long, cold trip."<ref name="Sobel1993">{{cite magazine |url=http://discovermagazine.com/1993/may/thelastworld215 |title=The Last World |magazine=Discover |first=Dava |last=Sobel |date=May 1993 |access-date=April 13, 2007 |archive-date=July 3, 2018 |archive-url=https://web.archive.org/web/20180703111150/http://discovermagazine.com/1993/may/thelastworld215 |url-status=live }}</ref> The call eventually led to a series of proposed Pluto missions leading up to ''New Horizons''.

[[Biography:Stamatios Krimigis|Stamatios "Tom" Krimigis]], head of the [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]]'s space division, one of many entrants in the New Frontiers Program competition, formed the ''New Horizons'' team with [[Biography:Alan Stern|Alan Stern]] in December 2000.  Appointed as the project's [[Principal investigator|principal investigator]], Stern was described by Krimigis as "the personification of the Pluto mission".<ref name="alan-stern">{{cite web |last1=Hand |first1=Eric |title=Feature: How Alan Stern's tenacity, drive, and command got a NASA spacecraft to Pluto |url=https://www.science.org/content/article/feature-how-alan-stern-s-tenacity-drive-and-command-got-nasa-spacecraft-pluto |website=Science |publisher=American Association for the Advancement of Science |date=June 25, 2015 |access-date=July 8, 2015 |archive-date=June 26, 2015 |archive-url=https://web.archive.org/web/20150626200636/http://news.sciencemag.org/people-events/2015/06/feature-how-alan-stern-s-tenacity-drive-and-command-got-nasa-spacecraft-pluto |url-status=live }}</ref> ''New Horizons'' was based largely on Stern's work since ''Pluto 350'' and involved most of the team from ''Pluto Kuiper Express''.<ref name="newhorizonsbook">[[Biography:Alan Stern|Stern, Alan]]; {{cite book |last1=Christopher |first1=Russell |title=New Horizons: Reconnaissance of the Pluto-Charon System and the Kuiper Belt |date=2009 |publisher=[[Company:Springer Publishing|Springer Publishing]] |isbn=978-0-387-89518-5 |pages=6, 7 |url=https://books.google.com/books?id=oZfpYIUKDrUC |access-date=July 8, 2015}}</ref>

The ''New Horizons'' proposal was one of five that officially submitted to NASA. It was later selected as one of two finalists to be subject to a three-month concept study in June 2001. The other finalist, POSSE (Pluto and Outer Solar System Explorer), was a separate but similar Pluto mission concept by the [[Organization:University of Colorado Boulder|University of Colorado Boulder]], led by principal investigator [[Biography:Larry W. Esposito|Larry W. Esposito]], and supported by the JPL, [[Company:Lockheed Martin|Lockheed Martin]] and the [[Organization:University of California|University of California]].<ref name="new-frontiers-finalists">{{cite news |last1=Savage |first1=Donald |url=http://nssdc.gsfc.nasa.gov/planetary/text/pluto_pr_20010606.txt |title=NASA Selects Two Investigations for Pluto-Kuiper Belt Mission Feasibility Studies |publisher=[[Organization:NASA|National Aeronautics and Space Administration (NASA)]] |date=June 6, 2001 |access-date=July 9, 2015 |archive-url=https://web.archive.org/web/20151231054106/http://nssdc.gsfc.nasa.gov/planetary/text/pluto_pr_20010606.txt |archive-date=December 31, 2015 |url-status=live}}</ref>

However, the APL, in addition to being supported by ''Pluto Kuiper Express'' developers at the Goddard Space Flight Center and [[Organization:Stanford University|Stanford University]]<ref name="new-frontiers-finalists"/> were at an advantage; they had recently developed ''[[Astronomy:NEAR Shoemaker|NEAR Shoemaker]]'' for NASA, which had successfully entered orbit around [[Astronomy:433 Eros|433 Eros]] earlier that year, and would later land on the asteroid to scientific and engineering fanfare.<ref>{{cite web |last1=Savage |first1=Donald |title=NEAR Shoemaker's Historic Landing on Eros Exceeds Science, Engineering Expectations |url=https://solarsystem.nasa.gov/news/display.cfm?News_ID=683 |website=[[Organization:NASA|National Aeronautics and Space Administration (NASA)]] |date=February 14, 2001 |access-date=July 8, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150709132201/https://solarsystem.nasa.gov/news/display.cfm?News_ID=683 |archive-date=July 9, 2015 }}</ref>

In November 2001, ''New Horizons'' was officially selected for funding as part of the New Frontiers program.<ref>{{cite news |last1=Savage |first1=Donald |url=http://nssdc.gsfc.nasa.gov/planetary/text/pluto_pr_20011129.txt |title=NASA Selects Pluto-Kuiper Belt Mission Phase B Study |publisher=[[Organization:NASA|National Aeronautics and Space Administration (NASA)]] |date=November 29, 2001 |access-date=July 9, 2015 |archive-url=https://web.archive.org/web/20110308190424/http://nssdc.gsfc.nasa.gov/planetary/text/pluto_pr_20011129.txt |archive-date=March 8, 2011 |url-status=live}}</ref> However, the new NASA Administrator appointed by the Bush administration, Sean O'Keefe, was not supportive of ''New Horizons'' and effectively canceled it by not including it in NASA's budget for 2003. NASA's Associate Administrator for the Science Mission Directorate, Ed Weiler, prompted Stern to lobby for the funding of ''New Horizons'' in hopes of the mission appearing in the [[Astronomy:Planetary Science Decadal Survey|Planetary Science Decadal Survey]], a prioritized "wish list,"compiled by the United States National Research Council, that reflects the opinions of the scientific community.<ref name="alan-stern"/>

After an intense campaign to gain support for ''New Horizons'', the Planetary Science Decadal Survey of 2003–2013 was published in the summer of 2002. ''New Horizons'' topped the list of projects considered the highest priority among the scientific community in the medium-size category; ahead of missions to the Moon, and even Jupiter. Weiler stated that it was a result that "[his] administration was not going to fight".<ref name="alan-stern"/> Funding for the mission was finally secured following the publication of the report. Stern's team was finally able to start building the spacecraft and its instruments, with a planned launch in January 2006 and arrival at Pluto in 2015.<ref name="alan-stern"/> Alice Bowman became Mission Operations Manager (MOM).<ref>{{cite web |url=http://www.jhuapl.edu/employment/meet/bowman.asp |title=Alice Bowman: APL's First Female MOM |publisher=Johns Hopkins Applied Physics Laboratory |access-date=April 11, 2016 |archive-date=May 11, 2018 |archive-url=https://web.archive.org/web/20180511193720/http://www.jhuapl.edu/employment/meet/bowman.asp |url-status=live }}</ref>

== Mission profile ==
[[File:15-011a-NewHorizons-PlutoFlyby-ArtistConcept-14July2015-20150115.jpg|thumb|upright|An artist's impression of ''New Horizons''{{'}} close encounter with the Plutonian system]]

''New Horizons'' is the first mission in NASA's New Frontiers mission category, larger and more expensive than the Discovery missions but smaller than the missions of the Flagship Program. The cost of the mission, including spacecraft and instrument development, launch vehicle, mission operations, data analysis, and education/public outreach, is approximately $700&nbsp;million over 15 years (2001–2016).<ref>{{Cite journal |url=https://www.forbes.com/sites/alexknapp/2015/07/14/how-do-new-horizons-costs-compare-to-other-space-missions/ |date=July 14, 2015 |title=How Do New Horizons Costs Compare To Other Space Missions? |first=Alex |last=Knapp |journal={{wipe|Forbes}}}}</ref> The spacecraft was built primarily by [[Organization:Southwest Research Institute|Southwest Research Institute]] (SwRI) and the [[Organization:Johns Hopkins University|Johns Hopkins]] Applied Physics Laboratory. The mission's principal investigator is [[Biography:Alan Stern|Alan Stern]] of the Southwest Research Institute (formerly NASA Associate Administrator).

After separation from the launch vehicle, overall control was taken by Mission Operations Center (MOC) at the Applied Physics Laboratory in Howard County, Maryland. The science instruments are operated at Clyde Tombaugh Science Operations Center (T-SOC) in Boulder, Colorado.<ref name="DoSS">{{cite web |title=Departments of Space Studies & Space Operations |work=Southwest Research Institute Planetary Science Directorate website |publisher=Southwest Research Institute |url=http://www.boulder.swri.edu/swri_boulder_2009a.pdf |access-date=March 14, 2010}}</ref> Navigation is performed at various contractor facilities, whereas the navigational positional data and related celestial reference frames are provided by the Naval Observatory Flagstaff Station through Headquarters NASA and [[Organization:JPL|JPL]].

[[Company:KinetX|KinetX]] is the lead on the ''New Horizons'' navigation team and is responsible for planning trajectory adjustments as the spacecraft speeds toward [[Astronomy:Solar System#Trans-Neptunian region|the outer Solar System]]. Coincidentally the Naval Observatory Flagstaff Station was where the photographic plates were taken for the discovery of Pluto's moon [[Astronomy:Charon (moon)|Charon]]. The Naval Observatory itself is not far from the [[Astronomy:Lowell Observatory|Lowell Observatory]] where Pluto was discovered.

''New Horizons'' was originally planned as a voyage to the only unexplored planet in the Solar&nbsp;System. When the spacecraft was launched, Pluto was still classified as a [[Astronomy:Planet|planet]], later to be [[Astronomy:IAU definition of planet|reclassified]] as a dwarf planet by the [[Organization:International Astronomical Union|International Astronomical Union]] (IAU). Some members of the ''New Horizons'' team, including Alan Stern, disagree with the IAU definition and still describe Pluto as the ninth planet.<ref>{{cite web |title=Unabashedly Onward to the Ninth Planet |work=New Horizons website |url=http://pluto.jhuapl.edu/overview/piPerspective.php?page=piPerspective_09_06_2006. |publisher=Johns Hopkins/APL |access-date=October 25, 2008 |archive-url=https://web.archive.org/web/20141113224857/http://pluto.jhuapl.edu/overview/piPerspective.php?page=piPerspective_09_06_2006 |archive-date=November 13, 2014 |url-status=dead }}</ref> Pluto's satellites Nix and Hydra also have a connection with the spacecraft: the first letters of their names (N and H) are the initials of ''New Horizons''. The moons' discoverers chose these names for this reason, plus Nix and Hydra's relationship to the mythological [[Religion:Pluto (mythology)|Pluto]].<ref>{{Cite press release |title=Pluto's Two Small Moons Christened Nix and Hydra |work=New Horizons website |publisher=Johns Hopkins APL |url=http://www.jhuapl.edu/newscenter/pressreleases/2006/060622.asp |access-date=October 25, 2008 |archive-url=https://web.archive.org/web/20110113182546/http://www.jhuapl.edu/newscenter/pressreleases/2006/060622.asp |url-status=dead |archive-date=January 13, 2011 }}</ref>

In addition to the science equipment, there are several cultural artifacts traveling with the spacecraft. These include a collection of 434,738 names stored on a compact disc,<ref>{{cite web |title=Send Your Name to Pluto |work=New Horizons website |publisher=Johns Hopkins APL |url=http://pluto.jhuapl.edu/spacecraft/searchName.php |access-date=January 30, 2009 |archive-url=https://web.archive.org/web/20141113224718/http://pluto.jhuapl.edu/spacecraft/searchName.php |archive-date=November 13, 2014 |url-status=dead }}</ref> a piece of [[Company:Scaled Composites|Scaled Composites]]'s ''[[Engineering:SpaceShipOne|SpaceShipOne]]'',<ref>{{Cite news |title=Pluto Mission to Carry Piece of SpaceShipOne |date=December 20, 2005 |work=Space.com |url=http://www.space.com/astronotes/astronotes.html |archive-url=https://web.archive.org/web/20101224201249/http://www.space.com/astronotes/astronotes.html |archive-date=December 24, 2010 |url-status=dead |access-date=January 17, 2006 }}</ref> a "Not Yet Explored" USPS stamp,<ref name="stamp-betz">{{cite web |last1=Betz |first1=Eric |title=Postage for Pluto: A 29-cent stamp pissed off scientists so much they tacked it to New Horizons |url=http://www.astronomy.com/year-of-pluto/2015/06/postage-for-pluto-a-29-cent-stamp-pissed-off-scientists-enough-they-tacked-it-to-new-horizons |website=[[Astronomy:Astronomy (magazine)|Astronomy]] |publisher=Kalmbach Publishing |date=June 26, 2015 |access-date=July 8, 2015}}</ref><ref name="stamp-070715">{{cite web |title='Not Yet Explored' no more: New Horizons flying Pluto stamp to dwarf planet |url=http://www.collectspace.com/news/news-070715a-newhorizons-pluto-explored-stamp.html |website=[[Organization:CollectSPACE|collectSPACE]] |publisher=Robert Pearlman |date=July 7, 2015 |access-date=July 8, 2015}}</ref> and a Flag of the United States, along with other mementos.<ref>{{Cite news |title=To Pluto, With Postage |date=October 28, 2008 |work=collectSPACE |url=http://www.collectspace.com/news/news-102808a.html |archive-url=https://web.archive.org/web/20101213192553/http://collectspace.com/news/news-102808a.html |archive-date=December 13, 2010 |url-status=live}}</ref>

About {{convert|1|oz|g|sigfig=1|order=flip}} of Clyde Tombaugh's ashes are aboard the spacecraft, to commemorate his discovery of Pluto in 1930.<ref>{{cite news |title=New Horizons launches on voyage to Pluto and beyond |url=http://www.spaceflightnow.com/atlas/av010/060119launch.html |work=spaceFlightNow |date=January 19, 2006 |access-date=December 1, 2010 |archive-url=https://web.archive.org/web/20110607074815/http://spaceflightnow.com/atlas/av010/060119launch.html |archive-date=June 7, 2011 |url-status=live}}</ref><ref>{{cite web |url=http://www.collectspace.com/news/news-102808a.html |title=To Pluto, with postage: Nine mementos fly with NASA's first mission to the last planet |publisher=collectSPACE |access-date=October 29, 2013 |archive-date=February 17, 2015 |archive-url=https://web.archive.org/web/20150217045712/http://www.collectspace.com/news/news-102808a.html |url-status=live }}</ref> A Florida-state quarter coin, whose design commemorates human exploration, is included, officially as a trim weight.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/newhorizons/main/fl_quarter.html |title=NASA – A 'State' of Exploration |publisher=Nasa.gov |date=March 8, 2006 |access-date=October 29, 2013}}</ref> One of the science packages (a dust counter) is named after [[Biography:Venetia Burney|Venetia Burney]], who, as a child, suggested the name "Pluto" after its discovery.

== Goal ==
[[File:15-150-NasaTeam-NewHorizonsCallsHomeAfterPlutoFlyby-20150714.jpg|thumb|right|View of Mission Operations at the Applied Physics Laboratory in Laurel, Maryland (July 14, 2015)]]
The goal of the mission is to understand the formation of the Plutonian system, the Kuiper belt, and the transformation of the early Solar System.<ref>{{cite web |url=http://www.nasa.gov/sites/default/files/files/AGU-NH-Workshop.pdf |title=The Everest of Planetary Exploration: New Horizons Explores The Pluto System 2015 |format=PowerPoint Presentation |work=NASA |access-date=April 15, 2015 |archive-date=July 10, 2015 |archive-url=https://web.archive.org/web/20150710185202/http://www.nasa.gov/sites/default/files/files/AGU-NH-Workshop.pdf |url-status=live }}</ref> The spacecraft collected data on the atmospheres, surfaces, interiors, and environments of Pluto and its moons. It will also study other objects in the Kuiper belt.<ref>{{cite web |url=https://solarsystem.nasa.gov/missions/profile.cfm?MCode=PKB |title=Solar System Exploration – New Horizons |work=NASA |date=February 27, 2015 |access-date=April 15, 2015 |archive-date=July 11, 2015 |archive-url=https://web.archive.org/web/20150711185410/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=PKB |url-status=live }}</ref> "By way of comparison, ''New Horizons'' gathered 5,000 times as much data at Pluto as [[Astronomy:Mariner program|Mariner]] did at the [[Astronomy:Mars|Red Planet]]."<ref>[https://www.bbc.com/news/science-environment-33440926 New Horizons: Pluto map shows 'whale' of a feature] {{Webarchive|url=https://web.archive.org/web/20170704010737/http://www.bbc.com/news/science-environment-33440926 |date=July 4, 2017 }} by Jonathan Amos, on July 8, 2015 (BBC – Science & Environment section)</ref>

Some of the questions the mission attempts to answer are: What is Pluto's atmosphere made of and how does it behave? What does its surface look like? Are there large geological structures? How do [[Astronomy:Solar wind|solar wind]] particles interact with Pluto's atmosphere?<ref>{{cite web |url=http://www.nasa.gov/mission_pages/newhorizons/spacecraft/index.html |title=New Horizons Spacecraft and Instruments |work=NASA |date=November 10, 2014 |access-date=April 15, 2015 |archive-date=July 11, 2015 |archive-url=https://web.archive.org/web/20150711010249/http://www.nasa.gov/mission_pages/newhorizons/spacecraft/index.html |url-status=live }}</ref>

Specifically, the mission's science objectives are to:<ref>{{cite web |url=http://discoverynewfrontiers.nasa.gov/missions/missions_nh.cfml |title=New Frontiers Program: New Horizons Science Objectives |work=NASA – New Frontiers Program |access-date=April 15, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150415224640/http://discoverynewfrontiers.nasa.gov/missions/missions_nh.cfml |archive-date=April 15, 2015 }}</ref>

*Map the surface compositions of Pluto and [[Astronomy:Charon (moon)|Charon]]
*Characterize the geologies and morphologies of Pluto and Charon
*Characterize the neutral [[Astronomy:Atmosphere of Pluto|atmosphere of Pluto]] and its escape rate
*Search for an atmosphere around Charon
*Map surface temperatures on Pluto and Charon
*Search for rings and additional satellites around Pluto
*Conduct similar investigations of one or more [[Astronomy:Kuiper belt|Kuiper belt]] objects

== Design and construction ==
[[File:New Horizons.stl|thumb|An interactive 3D model of ''New Horizons''|alt=Interactive 3D model of New Horizons]]

=== Spacecraft subsystems ===
[[File:New Horizons 1.jpg|thumb|''New Horizons'' in a factory at Kennedy Space Center in 2005]]
The spacecraft is comparable in size and general shape to a [[Engineering:Grand piano|grand piano]] and has been compared to a piano glued to a cocktail bar-sized satellite dish.<ref name="Moore-2010"/> As a point of departure, the team took inspiration from the Ulysses spacecraft,<ref>{{Cite journal |title=The New Horizons Spacecraft |journal=Space Science Reviews |last1=Fountain |first1=G. H. |last2=Kusnierkiewicz |first2=D. Y. |last3=Hersman |first3=C. B. |last4=Herder |first4=T. S. |last5=Coughlin |first5=T. B. |last6=Gibson |first6=W. C. |last7=Clancy |first7=D. A. |last8=Deboy |first8=C. C. |last9=Hill |first9=T. A. | last10=Kinnison |first10=J. D. |last11=Mehoke |first11=D. S. |last12=Ottman |first12=G. K. |last13=Rogers |first13=G. D. |last14=Stern |first14=S. A. |last15=Stratton |first15=J. M. |last16=Vernon |first16=S. R. |last17=Williams |first17=S. P. |display-authors=1 |volume=140 |issue=1–4 |pages=23–47 |year=2008 |arxiv=0709.4288 |doi=10.1007/s11214-008-9374-8 |bibcode=2008SSRv..140...23F|s2cid=119216290 }}</ref> which also carried a [[Physics:Radioisotope thermoelectric generator|radioisotope thermoelectric generator]] (RTG) and dish on a box-in-box structure through the outer Solar System. Many subsystems and components have flight heritage from APL's [[Astronomy:CONTOUR|CONTOUR]] spacecraft, which in turn had heritage from APL's [[Astronomy:TIMED|TIMED]] spacecraft.

''New Horizons''{{'}} body forms a triangle, almost {{cvt|2.5|ft|m|order=flip}} thick. (The ''Pioneers'' have [[Hexagon|hexagon]]al bodies, whereas the [[Astronomy:Voyager program|''Voyagers'']], ''Galileo'', and ''[[Astronomy:Cassini–Huygens|Cassini–Huygens]]'' have [[Decagon|decagon]]al, hollow bodies.) A [[Chemistry:7075 aluminium alloy|7075 aluminium alloy]] tube forms the main structural column, between the launch vehicle adapter ring at the "rear", and the {{cvt|2.1|m}} radio dish antenna affixed to the "front" flat side. The [[Chemistry:Titanium|titanium]] fuel tank is in this tube. The RTG attaches with a 4-sided titanium mount resembling a gray pyramid or stepstool.

Titanium provides strength and thermal isolation. The rest of the triangle is primarily sandwich panels of thin aluminum face sheet (less than {{cvt|1/64|in|mm|2|disp=or}}) bonded to aluminum honeycomb core. The structure is larger than strictly necessary, with empty space inside. The structure is designed to act as [[Engineering:Radiation hardening|shielding]], reducing electronics [[Engineering:Single event upset|errors caused by radiation]] from the RTG. Also, the mass distribution required for a spinning spacecraft demands a wider triangle.

The interior structure is painted black to equalize temperature by [[Physics:Thermal radiation|radiative]] heat transfer. Overall, the spacecraft is thoroughly blanketed to retain heat. Unlike the ''Pioneers'' and ''Voyagers'', the radio dish is also enclosed in blankets that extend to the body. The heat from the RTG adds warmth to the spacecraft while it is in the outer Solar System. While in the inner Solar System, the spacecraft must prevent overheating, hence electronic activity is limited, power is diverted to [[Engineering:Shunt (electrical)|shunts]] with attached radiators, and [[Engineering:Louver|louver]]s are opened to radiate excess heat. While the spacecraft is cruising inactively in the cold outer Solar System, the louvers are closed, and the shunt regulator reroutes power to electric [[Engineering:Resistor|heaters]].

==== Propulsion and attitude control ====
''New Horizons'' has both spin-stabilized (cruise) and three-axis stabilized (science) modes controlled entirely with [[Chemistry:Hydrazine|hydrazine]] [[Engineering:Monopropellant rocket|monopropellant]]. Additional post launch [[Astronomy:Delta-v|delta-''v'']] of over {{cvt|290|m/s|km/h mph}} is provided by a {{cvt|77|kg}} internal tank. Helium is used as a pressurant, with an [[Physics:Elastomer|elastomer]]ic diaphragm assisting expulsion. The spacecraft's on-orbit mass including fuel is over {{cvt|470|kg}} on the Jupiter flyby trajectory, but would have been only {{cvt|445|kg}} for the backup direct flight option to Pluto. Significantly, had the backup option been taken, this would have meant less fuel for later Kuiper belt operations.

There are 16 [[Engineering:Reaction control system|thrusters]] on ''New Horizons'': four {{cvt|4.4|N|lbf|1|lk=on}} and twelve {{cvt|0.9|N|lbf|1}} plumbed into redundant branches. The larger thrusters are used primarily for trajectory corrections, and the small ones (previously used on ''Cassini'' and the ''Voyager'' spacecraft) are used primarily for [[Astronomy:Spacecraft attitude control|attitude control]] and spinup/spindown maneuvers. Two star cameras are used to measure the spacecraft attitude. They are mounted on the face of the spacecraft and provide attitude information while in spin-stabilized or 3-axis mode. In between the time of star camera readings, spacecraft orientation is provided by dual redundant [[Engineering:Miniature inertial measurement unit|miniature inertial measurement unit]]s. Each unit contains three solid-state [[Engineering:Gyroscope|gyroscope]]s and three [[Physics:Accelerometer|accelerometer]]s. Two Adcole [[Astronomy:Spacecraft attitude control|Sun sensor]]s provide attitude determination. One detects the angle to the Sun, whereas the other measures spin rate and clocking.

==== Power ====
[[File:RTG and New Horizons in background.jpg|thumb|upright|''New Horizons''{{'}} [[Physics:Radioisotope thermoelectric generator|RTG]]]]

A cylindrical [[Physics:Radioisotope thermoelectric generator|radioisotope thermoelectric generator]] (RTG) protrudes in the plane of the triangle from one vertex of the triangle. The RTG provided {{val|245.7|ul=W}} of power at launch, and was predicted to drop approximately {{val|3.5|ul=W}} every year, decaying to {{val|202|u=W}} by the time of its encounter with the Plutonian system in 2015 and will decay too far to power the transmitters in the 2030s.<ref name="tri"/> There are no onboard batteries since RTG output is predictable, and load transients are handled by a capacitor bank and fast circuit breakers. As of January 2019, the power output of the RTG is about {{val|190|ul=W}}.<ref>{{cite web |title=New Horizons Systems and Components |url=http://pluto.jhuapl.edu/Mission/Spacecraft/Systems-and-Components.php}}</ref>

The RTG, model "[[Engineering:GPHS-RTG|GPHS-RTG]]", was originally a spare from the ''Cassini'' mission. The RTG contains {{cvt|9.75|kg|lb}} of [[Physics:Plutonium-238|plutonium-238]] oxide pellets.<ref name="newhorizonsbook"/> Each pellet is clad in [[Chemistry:Iridium|iridium]], then encased in a graphite shell. It was developed by the U.S. Department of Energy at the Materials and Fuels Complex, a part of the [[Organization:Idaho National Laboratory|Idaho National Laboratory]].<ref>{{Cite news |first=Steven |last=Friederich |title=Argonne Lab is developing battery for NASA missions |date=December 16, 2003 |publisher=Idaho State Journal |url=http://www.journalnet.com/articles/2003/12/16/news/local/news02.txt |archive-url=https://web.archive.org/web/20040119190022/http://www.journalnet.com/articles/2003/12/16/news/local/news02.txt |archive-date=January 19, 2004}} [http://www.matr.net/article-9139.html Alt URL]</ref>
The original RTG design called for  {{cvt|10.9|kg|lb}} of plutonium, but a unit less powerful than the original design goal was produced because of delays at the United States Department of Energy, including security activities, that delayed plutonium production.<ref name=radioshow>{{cite web |last1=Betts |first1=Bruce |title=Planetary Radio trivia question at 38m28s |url=http://www.planetary.org/multimedia/planetary-radio/show/2015/0728-the-royal-observatory-greenwich-quest-for-longitude.html |website=The Planetary Society |access-date=August 7, 2015}}</ref> The mission parameters and observation sequence had to be modified for the reduced wattage; still, not all instruments can operate simultaneously. The Department of Energy transferred the space battery program from Ohio to Argonne in 2002 because of security concerns.

The amount of radioactive plutonium in the RTG is about one-third the amount on board the Cassini–Huygens probe when it launched in 1997. The Cassini launch had been protested by multiple organizations, due to the risk of such a large amount of plutonium being released into the atmosphere in case of an accident. The United States Department of Energy estimated the chances of a launch accident that would release radiation into the atmosphere at 1 in 350, and monitored the launch<ref>{{cite news |url=http://www.foxnews.com/story/0,2933,181880,00.html |title=Pluto Probe Launch Scrubbed for Tuesday |work=Fox News |date=January 18, 2006 |archive-url=https://web.archive.org/web/20110223120321/http://www.foxnews.com/story/0,2933,181880,00.html |archive-date=February 23, 2011 |url-status=dead }}</ref> because of the inclusion of an RTG on board. It was estimated that a worst-case scenario of total dispersal of on-board plutonium would spread the equivalent radiation of 80% the average annual dosage in North America from background radiation over an area with a radius of {{cvt|105|km}}.<ref>{{cite web |title=Draft Environmental Impact Statement for the New Horizons Mission |url=http://pluto.jhuapl.edu/overview/deis/docs/NH_DEIS_Full.pdf |publisher=Johns Hopkins APL |access-date=May 16, 2014 |archive-url=https://web.archive.org/web/20141113230746/http://pluto.jhuapl.edu/overview/deis/docs/NH_DEIS_Full.pdf |archive-date=November 13, 2014 }}</ref>

==== Flight computer ====
The spacecraft carries two [[Computer|computer]] systems: the Command and Data Handling system and the Guidance and Control processor. Each of the two systems is duplicated for [[Engineering:Redundancy (engineering)|redundancy]], for a total of four computers. The processor used for its flight computers is the [[Mongoose-V]], a 12 [[Megahertz|MHz]] radiation-hardened version of the [[Engineering:R3000|MIPS R3000]] [[Central processing unit|CPU]]. Multiple redundant clocks and timing routines are implemented in hardware and software to help prevent faults and downtime. To conserve heat and mass, spacecraft and instrument electronics are housed together in IEMs (integrated electronics modules). There are two redundant IEMs. Including other functions such as instrument and radio electronics, each IEM contains 9&nbsp;boards.<ref>{{cite web |url=http://pluto.jhuapl.edu/Mission/Spacecraft/Systems-and-Components.php |title=New Horizons |work=jhuapl.edu}}</ref> The software of the probe runs on [[Software:Nucleus RTOS|Nucleus RTOS]] operating system.<ref>{{cite web |last1=Voica |first1=Alexandru |title=MIPS in space: Inside NASA's New Horizons mission to Pluto |url=http://blog.imgtec.com/mips-processors/mips-in-space-inside-nasa-new-horizons-mission-to-pluto |website=Imagination |access-date=October 18, 2015 |archive-date=October 17, 2015 |archive-url=https://web.archive.org/web/20151017204133/http://blog.imgtec.com/mips-processors/mips-in-space-inside-nasa-new-horizons-mission-to-pluto |url-status=dead }}</ref>

There have been two "safing" events, that sent the spacecraft into [[Engineering:Safe mode (spacecraft)|safe mode]]:
* On March 19, 2007, the Command and Data Handling computer experienced an uncorrectable memory error and rebooted itself, causing the spacecraft to go into safe mode. The craft fully recovered within two days, with some data loss on Jupiter's magnetotail. No impact on the subsequent mission was expected.<ref>{{cite web |title=The PI's Perspective: Trip Report |url=http://pluto.jhuapl.edu/News-Center/PI-Perspectives.php?page=piPerspective_3_26_2007 |date=March 27, 2007 |access-date=August 5, 2009 |publisher=NASA/Johns Hopkins University/APL/New Horizons Mission}}</ref>
* On July 4, 2015, there was a CPU safing event triggered by an over-assignment of commanded science operations on the craft's approach to Pluto. Fortunately, the craft was able to recover within two days without major impacts on its mission. NASA scientists therefore reduced the number of scientific operations on the craft to prevent future events, which could happen during the approach with Pluto.<ref>{{cite web |url=https://www.latimes.com/science/sciencenow/la-sci-sn-pluto-encounter-mode-20150706-story.html |title=Computer glitch doesn't stop New Horizons: Pluto encounter almost a week away |author=Los Angeles Times |date=July 6, 2015 |work=Los Angeles Times |access-date=July 13, 2015}}</ref><ref>{{cite web |url=http://www.space.com/29853-new-horizons-glitch-pluto-flyby.html |title=Pluto Probe Suffers Glitch 10 Days Before Epic Flyby |work=Space.com |date=July 5, 2015 |access-date=July 13, 2015}}</ref>

==== Telecommunications and data handling ====
[[File:New Horizons - REX.jpeg|thumb|''New Horizons''{{'}} [[Engineering:Antenna (radio)|antenna]], with some test equipment attached.]]

Communication with the spacecraft is via [[Physics:X band|X band]]. The craft had a communication rate of {{val|38|u=kbit/s}} at Jupiter; at Pluto's distance, a rate of approximately {{val|1|ul=kbit/s}} per transmitter was expected. Besides the low data rate, Pluto's distance also causes a [[Engineering:Latency (engineering)|latency]] of about 4.5&nbsp;hours (one-way). The {{cvt|70|m|adj=on|sp=us}} [[Astronomy:NASA Deep Space Network|NASA Deep Space Network]] (DSN) dishes are used to relay commands once the spacecraft is beyond Jupiter.  The spacecraft uses [[Dual modular redundancy|dual modular redundancy]] transmitters and receivers, and either right- or left-hand [[Astronomy:Circular polarization|circular polarization]].

The downlink signal is amplified by dual redundant 12-watt [[Engineering:Traveling-wave tube|traveling-wave tube]] amplifiers (TWTAs) mounted on the body under the dish. The receivers are low-power designs. The system can be controlled to power both TWTAs at the same time, and transmit a dual-polarized downlink signal to the DSN that nearly doubles the downlink rate. DSN tests early in the mission with this dual polarization combining technique were successful, and the capability was declared to be operational (when the spacecraft power budget permits both TWTAs to be powered).

In addition to the high-gain antenna, there are two backup low-gain antennas and a medium-gain dish. The high-gain dish has a [[Astronomy:Cassegrain reflector|Cassegrain reflector]] layout, composite construction, of {{convert|2.1|m|ft|0|adj=on|sp=us}} diameter providing over {{val|42|ul=dBi}} of gain and a half-power beam width of about a degree. The prime-focus medium-gain antenna, with a {{convert|0.3|m|ft|0|adj=on|sp=us}} aperture and 10° half-power beam width, is mounted to the forward-facing side of the high-gain antenna's secondary reflector. The forward low-gain antenna is stacked atop the feed of the medium-gain antenna. The aft low-gain antenna is mounted within the launch adapter at the rear of the spacecraft. This antenna was used only for early mission phases near Earth, just after launch and for emergencies if the spacecraft had lost attitude control.

''New Horizons'' recorded scientific instrument data to its solid-state memory buffer at each encounter, then transmitted the data to Earth. Data storage is done on two low-power [[Flash memory|solid-state recorders]] (one primary, one backup) holding up to {{val|8|ul=gigabyte}}s each. Because of the extreme distance from Pluto and the Kuiper belt, only one buffer load at those encounters can be saved. This is because ''New Horizons'' would require approximately 16 months after leaving the vicinity of Pluto to transmit the buffer load back to Earth.<ref name="JHU APL News Center 20150414">{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150414 |title=NASA's New Horizons Nears Historic Encounter with Pluto |publisher=Johns Hopkins University Applied Physics Laboratory |first1=Dwayne |last1=Brown |first2=Michael |last2=Buckley |first3=Maria |last3=Stothoff |date=April 14, 2015 |access-date=March 25, 2018 |archive-date=November 1, 2019 |archive-url=https://web.archive.org/web/20191101170955/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150414 |url-status=live }}</ref> At Pluto's distance, radio signals from the space probe back to Earth took four hours and 25 minutes to traverse 4.7&nbsp;billion km of space.<ref>{{cite news |url=https://www.bbc.com/news/science-environment-33531811 |title=New Horizons: Spacecraft survives Pluto encounter |publisher=BBC |last1=Rincon |first1=Paul |date=July 15, 2015}}</ref>

Part of the reason for the delay between the gathering of and transmission of data is that all of the ''New Horizons'' instrumentation is body-mounted. In order for the cameras to record data, the entire probe must turn, and the one-degree-wide beam of the high-gain antenna was not pointing toward Earth.  Previous spacecraft, such as the ''Voyager'' program probes, had a rotatable instrumentation platform (a "scan platform") that could take measurements from virtually any angle without losing radio contact with Earth.  ''New Horizons'' was mechanically simplified to save weight, shorten the schedule, and improve reliability during its 15-year designed lifetime.

The ''[[Astronomy:Voyager 2|Voyager 2]]'' scan platform jammed at Saturn, and the demands of long time exposures at outer planets led to a change of plans such that the entire probe was rotated to make photos at Uranus and Neptune, similar to how ''New Horizons'' rotated.

== Instruments ==
''New Horizons'' carries seven instruments: three optical instruments, two plasma instruments, a dust sensor and a radio science receiver/radiometer. The instruments are to be used to investigate the global geology, surface composition, surface temperature, atmospheric pressure, atmospheric temperature and escape rate of Pluto and its moons. The rated power is {{val|21|u=watts}}, though not all instruments operate simultaneously.<ref>{{Cite journal |author=Y. Guo |author2=R. W. Farquhar |journal=Acta Astronautica |volume=58 |issue=10 |date=2006 |pages=550–559 |doi=10.1016/j.actaastro.2006.01.012 |title=Baseline design of New Horizons mission to Pluto and the Kuiper belt |bibcode=2006AcAau..58..550G}}</ref> In addition, ''New Horizons'' has an Ultrastable Oscillator subsystem, which may be used to study and test the [[Astronomy:Pioneer anomaly|Pioneer anomaly]] towards the end of the spacecraft's life.<ref>{{Cite journal |author=M.M. Nieto |journal=Physics Letters B |volume=659 |issue=3 |date=2008 |pages=483–485 |doi=10.1016/j.physletb.2007.11.067 |title=New Horizons and the onset of the Pioneer anomaly |bibcode=2008PhLB..659..483N |arxiv=0710.5135|s2cid=18137697 }}</ref>

=== Long-Range Reconnaissance Imager (LORRI) ===
[[File:New Horizons LORRI.jpg|thumb|LORRI—long-range camera]]
{{Main|Astronomy:Long Range Reconnaissance Imager}}
The Long-Range Reconnaissance Imager (LORRI) is a long-focal-length imager designed for high resolution and responsivity at visible wavelengths. The instrument is equipped with a 1024×1024 pixel by 12-bits-per-pixel monochromatic [[Engineering:Charge-coupled device|CCD]] imager giving a resolution of 5&nbsp;μrad (~1&nbsp;[[Arcsecond|arcsec]]).<ref name=jhuapl-lorri>{{cite web |title=About LORRI Images |url=http://pluto.jhuapl.edu/soc/lorri_about.html |publisher=The Johns Hopkins University – Applied Physics Laboratory}}</ref> The CCD is chilled far below freezing by a passive radiator on the antisolar face of the spacecraft. This temperature differential requires insulation and isolation from the rest of the structure. The {{cvt|208.3|mm|in}} aperture Ritchey–Chretien mirrors and metering structure are made of [[Chemistry:Silicon carbide|silicon carbide]] to boost stiffness, reduce weight and prevent warping at low temperatures. The optical elements sit in a composite light shield and mount with titanium and fiberglass for thermal isolation. Overall mass is {{cvt|8.6|kg}}, with the optical tube assembly (OTA) weighing about {{cvt|5.6|kg}},<ref>{{cite web |url=http://www.boulder.swri.edu/pkb/ssr/ssr-lorri.pdf |title=Long-Range Reconnaissance Imager on New Horizons |first=A. F. |last=Cheng |display-authors=0 |archive-url=https://web.archive.org/web/20090709151428/http://www.boulder.swri.edu/pkb/ssr/ssr-lorri.pdf |archive-date=July 9, 2009 |url-status=dead }}</ref> for one of the largest silicon-carbide telescopes flown at the time (now surpassed by [[Astronomy:Herschel Space Observatory|Herschel]]). For viewing on public web sites the 12-bit per pixel LORRI images are converted to 8-bit per pixel [[JPEG]] images.<ref name=jhuapl-lorri/> These public images do not contain the full [[Dynamic range|dynamic range]] of brightness information available from the raw LORRI images files.<ref name=jhuapl-lorri/>
:{{small|''Principal investigator: Andy Cheng, [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]]''}}, {{small|''Data: LORRI image search at jhuapl.edu''<ref>{{cite web |url=http://pluto.jhuapl.edu/Multimedia/Science-Photos/search.php?form_keywords=60 |title=Science Photos: LORRI |work=JHUAPL.edu |access-date=May 2, 2015 |archive-url=https://web.archive.org/web/20150428072216/http://pluto.jhuapl.edu/Multimedia/Science-Photos/search.php?form_keywords=60 |archive-date=April 28, 2015 |url-status=dead }}</ref>}}

=== Solar Wind Around Pluto (SWAP) ===
[[File:New Horizons SWAP.jpg|thumb|[[Astronomy:SWAP (New Horizons)|SWAP]] – Solar Wind Around Pluto]]
{{Main|Astronomy:SWAP (New Horizons)}}
Solar Wind Around Pluto (SWAP) is a toroidal [[Physics:Electrostatic analyzer|electrostatic analyzer]] and retarding potential analyzer (RPA), that makes up one of the two instruments comprising ''New Horizons''{{'}} [[Physics:Plasma|Plasma]] and high-energy particle spectrometer suite (PAM), the other being PEPSSI. SWAP measures particles of up to 6.5&nbsp;keV and, because of the tenuous solar wind at Pluto's distance, the instrument is designed with the largest [[Astronomy:Aperture|aperture]] of any such instrument ever flown.<ref name="ProbeHomepage">{{cite web |url=http://pluto.jhuapl.edu/Mission/Spacecraft/index.php |title=New Horizons |website=pluto.jhuapl.edu |language=en |access-date=May 1, 2018 |archive-url=https://web.archive.org/web/20180501224827/http://pluto.jhuapl.edu/Mission/Spacecraft/index.php |archive-date=May 1, 2018 |url-status=dead }}</ref>
:{{small|''Principal investigator: David McComas, [[Organization:Southwest Research Institute|Southwest Research Institute]]''}}

=== Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) ===
{{Main|Astronomy:Pluto Energetic Particle Spectrometer Science Investigation}}
Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) is a [[Physics:Time-of-flight mass spectrometry|time of flight]] [[Physics:Ion|ion]] and [[Physics:Electron|electron]] sensor that makes up one of the two instruments comprising ''New Horizons''{{'}} plasma and high-energy particle spectrometer suite (PAM), the other being SWAP. Unlike SWAP, which measures particles of up to 6.5&nbsp;keV, PEPSSI goes up to 1&nbsp;MeV.<ref name="ProbeHomepage" /> The PEPSSI sensor has been designed to measure the mass, energy and distribution of charged particles around Pluto, and is also able to differentiate between [[Physics:Proton|proton]]s, [[Physics:Electron|electron]]s, and other heavy ions.<ref>{{Cite book |last=McNutt |first=Ralph |title=The Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) on the New Horizons Mission |publisher=Dordrecht: Springer Netherlands |year=2009 |pages=381}}</ref>
:{{small|''Principal investigator: Ralph McNutt Jr., Applied Physics Laboratory''}}

=== Alice ===
{{Main|Astronomy:Alice (spacecraft instrument)}}
''Alice'' is an [[Physics:Ultraviolet|ultraviolet]] imaging [[Physics:Spectrometer|spectrometer]] that is one of two photographic instruments comprising ''New Horizons''{{'}} Pluto Exploration Remote Sensing Investigation (PERSI); the other being the ''Ralph'' telescope. It resolves 1,024&nbsp;wavelength bands in the far and extreme ultraviolet (from 50–{{val|180|ul=nm}}), over 32&nbsp;view fields. Its goal is to determine the composition of Pluto's atmosphere. This Alice instrument is derived from another Alice aboard [[Organization:European Space Agency|ESA]]'s Rosetta spacecraft.<ref name="ProbeHomepage" /> The instrument has a mass of 4.4&nbsp;kg and draws 4.4 watts of power. Its primary role is to determine the relative concentrations of various elements and isotopes in Pluto's atmosphere.<ref>{{Cite book |last=Stern |first=Alan |title=ALICE: The Ultraviolet Imaging Spectrograph Aboard the New Horizons Pluto–Kuiper Belt Mission |publisher=Dordrecht: Springer Netherlands |year=2008 |pages=155–187}}</ref>
:{{small|''Principal investigator: Alan Stern, Southwest Research Institute''}} 
In August 2018, NASA confirmed, based on results by ''Alice'' on the ''New Horizons'' spacecraft, a "hydrogen wall" at the outer edges of the [[Astronomy:Solar System|Solar System]] that was first detected in 1992 by the two [[Astronomy:Voyager program|Voyager spacecraft]].<ref name="GRL-20180807" /><ref name="LS-20180809" />

=== Ralph telescope ===
[[File:New Horizons - Ralph.png|thumb|''Ralph''—telescope and color camera]]
{{Main|Astronomy:Ralph (New Horizons)}}
The Ralph telescope,  75&nbsp;mm<ref>{{cite web |title=Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission |url=https://www.boulder.swri.edu/pkb/ssr/ssr-ralph.pdf |website=boulder.swri.edu |access-date=16 August 2021}}</ref> in aperture, is one of two photographic instruments that make up ''New Horizons''{{'}} Pluto Exploration Remote Sensing Investigation (PERSI), with the other being the Alice instrument. Ralph has two separate channels: MVIC (Multispectral Visible Imaging Camera), a visible-light [[Engineering:Charge-coupled device|CCD]] imager with broadband and color channels; and LEISA (Linear Etalon Imaging Spectral Array), a near-[[Physics:Infrared|infrared]] imaging spectrometer. LEISA is derived from a similar instrument on the [[Engineering:Earth Observing-1|Earth Observing-1]] spacecraft. Ralph was named after Alice's husband on ''The Honeymooners'', and was designed after Alice.<ref name="sn20150711">{{cite news |url=http://spacenews.com/new-horizons-about-to-bring-an-unknown-world-into-sharp-focus/ |title=Meet Ralph, the New Horizons Camera Bringing Pluto into Sharp Focus |work=Space News |last1=David |first1=Leonard |date=July 11, 2015 |access-date=July 16, 2015}}</ref>

On June 23, 2017, NASA announced that it has renamed the LEISA instrument to the "Lisa Hardaway Infrared Mapping Spectrometer" in honor of Lisa Hardaway, the Ralph program manager at Ball Aerospace, who died in January 2017 at age 50.<ref name="nasa20170623">{{cite web |url=https://www.nasa.gov/feature/nasa-s-new-horizons-mission-honors-memory-of-engineer-lisa-hardaway |title=NASA's New Horizons Mission Honors Memory of Engineer Lisa Hardaway |publisher=NASA |editor-first=Lillian |editor-last=Gipson |date=June 23, 2017 |access-date=June 27, 2017}}</ref>
:{{small|''Principal investigator: Alan Stern, Southwest Research Institute''}}

=== Venetia Burney Student Dust Counter (VBSDC) ===
[[File:New Horizons sdc.jpeg|thumb|VBSDC—Venetia Burney Student Dust Counter]]

The [[Astronomy:Venetia Burney Student Dust Counter|Venetia Burney Student Dust Counter]] (VBSDC), built by students at the University of Colorado Boulder, is operating periodically to make [[Astronomy:Cosmic dust|dust]] measurements.<ref>{{cite web |title=Pluto-Bound, Student-Built Dust Detector Renamed "Venetia," Honoring Girl Who Named Ninth Planet |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=062906 |publisher=The Johns Hopkins University Applied Physics Laboratory}}</ref><ref>{{cite journal |last1=Poppe |first1=Andrew R. |last2=James |first2=David |last3=Jacobsmeyer |first3=Brian |last4=Horanyi |first4=Mihaly |title=Measurements of the Interplanetary Dust Population by the Venetia Burney Student Dust Counter on the New Horizons Mission |journal=41st Annual Lunar and Planetary Science Conference |year=2010 |issue=1533 |page=1219 |bibcode=2010LPI....41.1219P |url=http://www.unmannedspaceflight.com/index.php?act=attach&type=post&id=21744 |access-date=28 March 2022}}</ref> It consists of a detector panel, about {{cvt|18|x|12|in|mm|order=flip}}, mounted on the anti-solar face of the spacecraft (the ram direction), and an electronics box within the spacecraft. The detector contains fourteen polyvinylidene difluoride (PVDF) panels, twelve science and two reference, which generate voltage when impacted. Effective collecting area is {{cvt|0.125|m2}}. No dust counter has operated past the orbit of [[Astronomy:Uranus|Uranus]]; models of dust in the outer Solar System, especially the Kuiper belt, are speculative. The VBSDC is always turned on measuring the masses of the interplanetary and interstellar dust particles (in the range of nano- and picograms) as they collide with the PVDF panels mounted on the ''New Horizons'' spacecraft. The measured data is expected to greatly contribute to the understanding of the dust spectra of the Solar System. The dust spectra can then be compared with those from observations of other stars, giving new clues as to where Earth-like planets can be found in the universe. The dust counter is named for [[Biography:Venetia Burney|Venetia Burney]], who first suggested the name "Pluto" at the age of 11. A thirteen-minute short film about the VBSDC garnered an Emmy Award for student achievement in 2006.<ref>{{cite web |url=https://www.youtube.com/watch?v=nes3cAh8_DI |title=Destination: Pluto and Beyond |work=YouTube.com |archive-url=https://web.archive.org/web/20140619180449/http://www.youtube.com/watch?v=nes3cAh8_DI |archive-date=June 19, 2014 |url-status=dead }}</ref>
:{{small|''Principal investigator: Mihaly Horanyi, [[Organization:University of Colorado Boulder|University of Colorado Boulder]]''}}

=== Radio Science Experiment (REX) ===
{{Main|Astronomy:REX (New Horizons)}}
The Radio Science Experiment (REX) used an ultrastable [[Engineering:Crystal oscillator|crystal oscillator]] (essentially a calibrated crystal in a miniature [[Physics:Crystal oven|oven]]) and some additional electronics to conduct radio science investigations using the communications channels. These are small enough to fit on a single card. Because there are two redundant communications subsystems, there are two, identical REX circuit boards.
:{{small|''Principal investigators: Len Tyler and Ivan Linscott, [[Organization:Stanford University|Stanford University]]''}}
{{Clear}}

== Journey to Pluto ==
{{Main|Astronomy:Timeline of New Horizons}}

=== Launch ===
{{multiple image |direction=horizontal |align=right |total_width=300
 |image1=NewHorizons Rocket Bly.jpg
 |image2=Atlas V 551 roars into blue sky.jpg
 |footer=Launch of ''New Horizons''. The [[Engineering:Atlas V|Atlas V]] rocket on the launchpad (left) and lift off from Cape Canaveral.
}}

On September 24, 2005, the spacecraft arrived at the Kennedy Space Center on board a C-17 Globemaster III for launch preparations.<ref name="SpaceDaily">{{cite web |url=http://www.spacedaily.com/reports/NASAS_Pluto_Space_Probe_Begins_Launch_Preparations.html |title=NASA'S Pluto Space Probe Begins Launch Preparations |publisher=SpaceDaily |date=September 27, 2005 |access-date=January 12, 2011 |archive-url=https://web.archive.org/web/20091231125211/http://www.spacedaily.com/reports/NASAS_Pluto_Space_Probe_Begins_Launch_Preparations.html |archive-date=December 31, 2009 |url-status=dead }}</ref> The launch of ''New Horizons'' was originally scheduled for January 11, 2006, but was initially delayed until January 17, 2006, to allow for [[Physics:Borescope|borescope]] inspections of the [[Engineering:Atlas V|Atlas V]]'s [[Chemistry:Kerosene|kerosene]] tank. Further delays related to low cloud ceiling conditions [[Engineering:Downrange|downrange]], and high winds and technical difficulties—unrelated to the rocket itself—prevented launch for a further two days.<ref name="nytimes.com">{{cite news |url=https://www.nytimes.com/2006/01/17/science/winds-delay-launching-for-nasa-mission-to-pluto.html |title=Winds Delay Launching for NASA Mission to Pluto |work=The New York Times |first=Warren E. |last=Leary |date=January 17, 2006}}</ref><ref name="Space.com">{{cite web |url=http://www.space.com/1957-launch-nasa-pluto-probe-delayed-24-hours.html |title=Launch of NASA's Pluto Probe Delayed for 24 Hours |work=Space.com |date=January 17, 2006 |access-date=June 3, 2013}}</ref>

The probe finally lifted off from Pad 41 at {{wipe|Cape Canaveral Air Force Station}}, Florida, directly south of [[Engineering:Space Shuttle|Space Shuttle]] Launch Complex 39, at 19:00&nbsp;UTC on January 19, 2006.<ref name="Amir">{{cite web |url=http://www.planetary.org/news/2006/0119_New_Horizons_Launched_on_its_Way_to.html |title=New Horizons Launched on its Way to Pluto |publisher=The Planetary Society |first=Amir |last=Alexander |date=January 19, 2006 |archive-url=https://web.archive.org/web/20120318214956/http://www.planetary.org/news/2006/0119_New_Horizons_Launched_on_its_Way_to.html |archive-date=March 18, 2012}}</ref><ref name="Harwood">{{cite news |url=http://spaceflightnow.com/atlas/av010/060119launch.html |title=New Horizons launches on voyage to Pluto and beyond |work=Spaceflight Now |last=Harwood |first=William |date=January 19, 2006 |access-date=January 12, 2011 |archive-url=https://web.archive.org/web/20101130001152/http://spaceflightnow.com/atlas/av010/060119launch.html |archive-date=November 30, 2010 |url-status=live}}</ref> The [[Engineering:Centaur (rocket stage)|Centaur]] second stage ignited at 19:04:43&nbsp;UTC and burned for 5 minutes 25 seconds. It reignited at 19:32&nbsp;UTC and burned for 9 minutes 47 seconds. The [[Company:Alliant Techsystems|ATK]] [[Astronomy:Star 48|Star 48]]B third stage ignited at 19:42:37&nbsp;UTC and burned for 1 minute 28 seconds.<ref name="ils200601">{{cite web |url=http://pluto.jhuapl.edu/Mission/The-Path-to-Pluto/FINAL-PLUTO_MO.pdf |title=New Horizons: Mission Overview |publisher=International Launch Services |date=January 2006 |access-date=April 21, 2018 |archive-url=https://web.archive.org/web/20160909024832/http://pluto.jhuapl.edu/Mission/The-Path-to-Pluto/FINAL-PLUTO_MO.pdf |archive-date=September 9, 2016 |url-status=dead }}</ref> Combined, these burns successfully sent the probe on a solar-escape trajectory at {{convert|16.26|km/s|km/h mph|0|sp=us}}.<ref name="sciam20130225" /> ''New Horizons'' took only nine hours to pass the Moon's orbit.<ref name="airspace20150710">{{cite magazine |url=https://airandspace.si.edu/stories/editorial/first-mission-pluto-difficult-birth-new-horizons |title=First Mission to Pluto: The Difficult Birth of New Horizons |magazine=Smithsonian |first=Michael |last=Neufeld |date=July 10, 2015 |access-date=April 21, 2018}}</ref> Although there were backup launch opportunities in February 2006 and February 2007, only the first twenty-three days of the 2006 window permitted the Jupiter flyby. Any launch outside that period would have forced the spacecraft to fly a slower trajectory directly to Pluto, delaying its encounter by five to six years.<ref name="nasa20150702">{{cite web |url=https://www.nasa.gov/feature/nasa-met-unprecedented-challenges-sending-spacecraft-to-pluto |title=NASA Met Unprecedented Challenges Sending Spacecraft to Pluto |publisher=NASA |first=Bob |last=Granath |date=July 2, 2015 |access-date=April 21, 2018}}</ref>

The probe was launched by a [[Company:Lockheed Martin|Lockheed Martin]] Atlas V 551 rocket, with a third stage added to increase the heliocentric (escape) speed. This was the first launch of the Atlas V 551 configuration, which uses five [[Engineering:Solid rocket booster|solid rocket booster]]s, and the first Atlas V with a third stage. Previous flights had used zero, two, or three solid boosters, but never five. The vehicle, AV-010, weighed {{convert|573160|kg|lb|sp=us}} at lift-off,<ref name="ils200601" /> and had earlier been slightly damaged when Hurricane Wilma swept across Florida on October 24, 2005. One of the solid rocket boosters was hit by a door. The booster was replaced with an identical unit, rather than inspecting and requalifying the original.<ref>{{cite news |url=http://spaceflightnow.com/atlas/av010/051102srbreplace.html |title=Damage prompts booster replacement for Pluto probe |work=Spaceflight Now |first=Justin |last=Ray |date=November 2, 2005 |access-date=July 31, 2007 |archive-url=https://web.archive.org/web/20110424103844/http://spaceflightnow.com/atlas/av010/051102srbreplace.html |archive-date=April 24, 2011 |url-status=dead }}</ref>

The launch was dedicated to the memory of launch conductor Daniel Sarokon, who was described by space program officials as one of the most influential people in the history of space travel.<ref>{{cite web |url=http://triblive.com/x/leadertimes/news/s_414000.html |title=Spacecraft will carry memory of Sagamore native |publisher=TribLIVE |first=Patrick |last=Schuster |date=January 16, 2006 |access-date=June 3, 2013}}</ref>

=== Inner Solar System ===

==== Trajectory corrections ====
On January 28 and 30, 2006, mission controllers guided the probe through its first [[Physics:Trajectory|trajectory]]-correction maneuver (TCM), which was divided into two parts (TCM-1A and TCM-1B). The total velocity change of these two corrections was about {{convert|18|m/s|km/h mph|sp=us}}. TCM-1 was accurate enough to permit the cancellation of TCM-2, the second of three originally scheduled corrections.<ref>{{cite web |url=http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_1_31_2006.php |title=Our Aim Is True |work=The PI's Perspective |publisher=Johns Hopkins APL |first=Alan |last=Stern |date=January 31, 2006 |access-date=June 11, 2006 |archive-url=https://web.archive.org/web/20141010030345/http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_1_31_2006.php |archive-date=October 10, 2014 |url-status=dead }}</ref> On March 9, 2006, controllers performed TCM-3, the last of three scheduled course corrections. The engines burned for 76&nbsp;seconds, adjusting the spacecraft's velocity by about {{cvt|1.16|m/s|km/h mph}}.<ref>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/030906.php |title=New Horizons Adjusts Course Towards Jupiter |publisher=Johns Hopkins APL |date=March 9, 2006 |access-date=May 29, 2011 |archive-url=https://web.archive.org/web/20141113224837/http://pluto.jhuapl.edu/news_center/news/030906.php |url-status=dead |archive-date=November 13, 2014}}</ref> Further trajectory maneuvers were not needed until September 25, 2007 (seven months after the Jupiter flyby), when the engines were fired for 15&nbsp;minutes and 37&nbsp;seconds, changing the spacecraft's velocity by {{cvt|2.37|m/s|km/h mph}},<ref>{{cite press release |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=092707 |title=Maneuver Puts New Horizons on a Straight Path to Pluto |publisher=Johns Hopkins APL |date=September 27, 2007 |access-date=July 16, 2015 |archive-url=https://web.archive.org/web/20080725071941/http://pluto.jhuapl.edu/news_center/news/092707.html |url-status=live |archive-date=July 25, 2008}}</ref> followed by another TCM, almost three years later on June 30, 2010, that lasted 35.6&nbsp;seconds, when ''New Horizons'' had already reached the halfway point (in time traveled) to Pluto.<ref>{{cite press release |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20100701 |title=Course Correction Keeps New Horizons on Path to Pluto |publisher=Johns Hopkins APL |date=July 1, 2010 |access-date=July 16, 2015 |archive-url=https://web.archive.org/web/20141113224818/http://pluto.jhuapl.edu/news_center/news/20100701.php |archive-date=November 13, 2014 |url-status=live}}</ref>

==== In-flight tests and crossing of Mars orbit ====
During the week of February 20, 2006, controllers conducted initial in-flight tests of three onboard science instruments, the Alice ultraviolet imaging spectrometer, the PEPSSI plasma-sensor, and the LORRI long-range visible-spectrum camera. No scientific measurements or images were taken, but instrument electronics, and in the case of Alice, some electromechanical systems were shown to be functioning correctly.<ref>{{cite web |author=Stern, Alan |date=February 27, 2006 |title=Boulder and Baltimore |work=The PI's Perspective |url=http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_2_27_2006.php |publisher=Johns Hopkins APL |access-date=June 11, 2006 |archive-url=https://web.archive.org/web/20060901080153/http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_2_27_2006.php |archive-date=September 1, 2006 |url-status=dead }}</ref>

On April 7, 2006, the spacecraft passed the orbit of Mars, moving at roughly {{cvt|21|km/s|km/h mph}} away from the Sun at a solar distance of 243 million kilometers.<ref name="Malik">{{cite news |last=Malik |first=T. |title=Pluto-Bound Probe Passes Mars' Orbit |work=Space.com |date=April 7, 2006 |url=http://www.space.com/2263-pluto-bound-probe-passes-mars-orbit.html |access-date=January 14, 2011 |archive-url=https://web.archive.org/web/20111127062040/http://www.space.com/2263-pluto-bound-probe-passes-mars-orbit.html |archive-date=November 27, 2011 |url-status=dead }}</ref><ref>{{Cite news |title=Outbound for the Frontier, New Horizons Crosses the Orbit of Mars |date=April 7, 2006 |publisher=Johns Hopkins APL |url=https://solarsystem.nasa.gov/news/display.cfm?News_ID=14396 |url-status=dead |archive-url=https://web.archive.org/web/20150213042523/https://solarsystem.nasa.gov/news/display.cfm?News_ID=14396 |archive-date=February 13, 2015 }}</ref><ref>{{cite web |title=Outbound for the Frontier, NASA New Horizons Crosses the Orbit of Mars |work=Pluto Today |publisher=SpaceRef Interactive Inc. |date=April 7, 2006 |url=http://www.plutotoday.com/news/viewsr.html?pid=20190 |access-date=February 3, 2013 |archive-url=https://web.archive.org/web/20060426224005/http://www.plutotoday.com/news/viewsr.html?pid=20190 |archive-date=April 26, 2006}}</ref>

==== Asteroid 132524 APL ====
{{multiple image |direction=horizontal |align=right |total_width=300
 |image1=Asteroid 2002 JF56.jpg |caption1=Asteroid [[Astronomy:132524 APL|132524 APL]] viewed by ''New Horizons'' in June 2006
 |image2=First Pluto sighting from New Horizons.gif |caption2=First images of Pluto in September 2006
}}

Because of the need to conserve fuel for possible encounters with Kuiper belt objects subsequent to the Pluto flyby, intentional encounters with objects in the [[Astronomy:Asteroid belt|asteroid belt]] were not planned. After launch, the ''New Horizons'' team scanned the spacecraft's trajectory to determine if any asteroids would, by chance, be close enough for observation. In May 2006 it was discovered that ''New Horizons'' would pass close to the tiny asteroid [[Astronomy:132524 APL|132524 APL]] on June 13, 2006. Closest approach occurred at 4:05&nbsp;UTC at a distance of {{cvt|101,867|km|mi}} (around one quarter of the [[Astronomy:Lunar distance|average Earth-Moon distance]]). The asteroid was imaged by Ralph (use of LORRI was not possible because of proximity to the Sun), which gave the team a chance to test Ralph{{'s}} capabilities, and make observations of the asteroid's composition as well as light and phase curves. The asteroid was estimated to be {{cvt|2.5|km|mi}} in diameter.<ref>{{cite web |author=Stern, Alan |date=June 1, 2006 |title=A Summer's Crossing of the Asteroid Belt |series=The PI's Perspective |publisher=Johns Hopkins APL |url=http://pluto.jhuapl.edu/overview/piPerspective.php?page=piPerspective_6_1_2006 |access-date=June 20, 2010 |archive-url=https://web.archive.org/web/20141113224821/http://pluto.jhuapl.edu/overview/piPerspective.php?page=piPerspective_6_1_2006 |archive-date=November 13, 2014 |url-status=dead }}</ref><ref>{{cite web |title=JF56 Encounter, Encounter Date June 13, 2006 UT |work=Pluto New Horizons Mission, Supporting Observations for 2002 |publisher=International Astronomical Union |url=http://smass.mit.edu/2002jf56.html |archive-url=https://web.archive.org/web/20070805184931/http://smass.mit.edu/2002jf56.html |archive-date=August 5, 2007 |access-date=June 20, 2010}}</ref><ref name="JHAPL61506">{{cite web |title=New Horizons Tracks an Asteroid |publisher=Johns Hopkins APL |url=http://pluto.jhuapl.edu/news_center/news/061506.php |date=June 15, 2006 |access-date=June 20, 2010 |archive-url=https://web.archive.org/web/20141113224827/http://pluto.jhuapl.edu/news_center/news/061506.php |archive-date=November 13, 2014 |url-status=dead }}</ref> The spacecraft successfully tracked the rapidly moving asteroid over June 10–12, 2006.

==== First Pluto sighting ====
The first images of Pluto from ''New Horizons'' were acquired September 21–24, 2006, during a test of LORRI. They were released on November 28, 2006.<ref name="LORRI">{{cite web |author=K. Beisser |title=New Horizons, Not Quite to Jupiter, Makes First Pluto Sighting |url=http://pluto.jhuapl.edu/news_center/news/112806.php |publisher=JHU/APL |date=November 28, 2006 |access-date=January 13, 2011 |archive-url=https://web.archive.org/web/20141113224846/http://pluto.jhuapl.edu/news_center/news/112806.php |archive-date=November 13, 2014 |url-status=dead }}</ref> The images, taken from a distance of approximately {{convert|4.2|e9km|e9mi+AU|abbr=unit}}, confirmed the spacecraft's ability to track distant targets, critical for maneuvering toward Pluto and other Kuiper belt objects.

=== Jupiter encounter ===
{{Main|Astronomy:Exploration of Jupiter}}
[[File:NH Jupiter IR (contrast enhanced).jpg|thumb|upright=0.6|Infrared image of Jupiter by ''New Horizons'']]
''New Horizons'' used LORRI to take its first photographs of Jupiter on September 4, 2006, from a distance of {{convert|291|e6km|abbr=off|sp=us}}.<ref>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/092606.html |title=Jupiter Ahoy! |publisher=Johns Hopkins APL |date=September 26, 2006 |access-date=October 27, 2008 |archive-url=https://web.archive.org/web/20080907192302/http://pluto.jhuapl.edu/news_center/news/092606.html |archive-date=September 7, 2008 |url-status=dead }}</ref> More detailed exploration of the system began in January 2007 with an infrared image of the moon [[Astronomy:Callisto (moon)|Callisto]], as well as several black-and-white images of Jupiter itself.<ref name=jupiter-encounter>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/011007.php |title=Jupiter Encounter Begins |publisher=Johns Hopkins APL |access-date=December 17, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224807/http://pluto.jhuapl.edu/news_center/news/011007.php |archive-date=November 13, 2014 }}</ref> ''New Horizons'' received a gravity assist from Jupiter, with its closest approach at 05:43:40&nbsp;UTC on February 28, 2007, when it was {{convert|2.3|e6km|abbr=off|sp=us}} from Jupiter. The flyby increased ''New Horizons''{{'}} speed by {{cvt|4|km/s|km/h mph|-3}}, accelerating the probe to a velocity of {{cvt|23|km/s|km/h mph|-3}} relative to the Sun and shortening its voyage to Pluto by three years.<ref name=boost>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/022807.php |title=Pluto-Bound New Horizons Spacecraft Gets a Boost from Jupiter |publisher=Johns Hopkins APL |date=February 28, 2007 |access-date=December 17, 2008 |archive-url=https://web.archive.org/web/20141113224828/http://pluto.jhuapl.edu/news_center/news/022807.php |archive-date=November 13, 2014}}</ref>

The flyby was the center of a four-month intensive observation campaign lasting from January to June. Being an ever-changing scientific target, Jupiter has been observed intermittently since the end of the ''[[Engineering:Galileo (spacecraft)|Galileo]]'' mission in September 2003. Knowledge about Jupiter benefited from the fact that ''New Horizons''{{'}} instruments were built using the latest technology, especially in the area of cameras, representing a significant improvement over ''Galileo''{{'s}} cameras, which were modified versions of ''[[Astronomy:Voyager 1|Voyager]]'' cameras, which, in turn, were modified ''[[Astronomy:Mariner program|Mariner]]'' cameras. The Jupiter encounter also served as a shakedown and dress rehearsal for the Pluto encounter. Because Jupiter is much closer to Earth than Pluto, the communications link can transmit multiple loadings of the memory buffer; thus the mission returned more data from the Jovian system than it was expected to transmit from Pluto.<ref>{{cite web |url=https://www.nbcnews.com/id/17381933 |title=Pluto probe gets an eyeful in Jupiter flyby |work=NBC News |first=Tariq |last=Malik |date=February 28, 2007 |access-date=May 29, 2011 }}</ref>

One of the main goals during the Jupiter encounter was observing its [[Astronomy:Atmosphere of Jupiter|atmospheric conditions]] and analyzing the structure and composition of its clouds. Heat-induced lightning strikes in the polar regions and "waves" that indicate violent storm activity were observed and measured. The Little Red Spot, spanning up to 70% of Earth's diameter, was imaged from up close for the first time.<ref name=boost/> Recording from different angles and illumination conditions, ''New Horizons'' took detailed images of Jupiter's faint [[Astronomy:Rings of Jupiter|ring system]], discovering debris left over from recent collisions within the rings or from other unexplained phenomena. The search for undiscovered moons within the rings showed no results. Travelling through Jupiter's [[Astronomy:Magnetosphere of Jupiter|magnetosphere]], ''New Horizons'' collected valuable particle readings.<ref name=boost/> "Bubbles" of plasma that are thought to be formed from material ejected by the moon Io were noticed in the magnetotail.<ref name=surf>{{cite news |last=Than |first=Ker |date=October 9, 2007 |title=Spacecraft Surfs Jupiter's Magnetic Tail |url=http://www.space.com/4446-spacecraft-surfs-jupiter-magnetic-tail.html |newspaper=Space.com |access-date=December 17, 2013}}</ref>

==== Jovian moons ====
The four largest moons of Jupiter were in poor positions for observation; the necessary path of the gravity-assist maneuver meant that ''New Horizons'' passed millions of kilometers from any of the [[Astronomy:Galilean moons|Galilean moons]]. Still, its instruments were intended for small, dim targets, so they were scientifically useful on large, distant moons. Emphasis was put on Jupiter's innermost Galilean moon, [[Astronomy:Io (moon)|Io]], whose active volcanoes shoot out tons of material into Jupiter's magnetosphere, and further. Out of eleven observed eruptions, three were seen for the first time. That of [[Astronomy:Tvashtar Paterae|Tvashtar]] reached an altitude of up to {{cvt|330|km}}. The event gave scientists an unprecedented look into the structure and motion of the rising plume and its subsequent fall back to the surface. Infrared signatures of a further 36 volcanoes were noticed.<ref name=boost/> [[Astronomy:Callisto (moon)|Callisto]]'s surface was analyzed with LEISA, revealing how lighting and viewing conditions affect infrared spectrum readings of its surface water ice.<ref>{{cite web |url=http://pluto.jhuapl.edu/gallery/sciencePhotos/image.php?page=4&gallery_id=2&image_id=21 |title=Capturing Callisto |publisher=Johns Hopkins APL |access-date=December 17, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224826/http://pluto.jhuapl.edu/gallery/sciencePhotos/image.php?page=4&gallery_id=2&image_id=21 |archive-date=November 13, 2014 }}</ref> Minor moons such as [[Astronomy:Amalthea (moon)|Amalthea]] had their orbit solutions refined. The cameras determined their positions, acting as "reverse optical navigation".

{{Multiple image |align=center |total_width=800
 |header=Jovian moons imaged by ''New Horizons''
 |image1=Tvashtar volcano on Io from New Horizons.jpg |caption1=[[Astronomy:Io (moon)|Io]] imaged on February 28, 2007. The feature near the north pole of the moon is a {{cvt|290|km|sp=us}} high plume from the volcano [[Astronomy:Tvashtar Paterae|Tvashtar]].
 |image2=PIA09246.jpg |caption2=[[Astronomy:Europa (moon)|Europa]] imaged on February 27, 2007, from a distance of {{convert|3.1|e6km|abbr=unit}}. Image scale is {{cvt|15|km|mi|disp=x| per pixel (|/px)}}.
 |image3=PIA09245 modest.jpg |caption3=[[Astronomy:Ganymede (moon)|Ganymede]] imaged on February 27, 2007, from a distance of {{convert|3.5|e6km|abbr=unit}}. Image scale is {{cvt|17|km|mi|disp=x| per pixel (|/px)}}.
 |image4=PIA09258 Callisto.jpg |caption4=[[Astronomy:Callisto (moon)|Callisto]] imaged on February 27, 2007, from a distance of {{convert|4.7|e6km|abbr=unit}}.
}}

=== Outer Solar System ===
After passing Jupiter, ''New Horizons'' spent most of its journey towards Pluto in hibernation mode. Redundant components as well as guidance and control systems were shut down to extend their life cycle, decrease operation costs and free the Deep Space Network for other missions.<ref name=hibernation1>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/062807.php |title=New Horizons Slips into Electronic Slumber |publisher=Johns Hopkins APL |date=2007 |access-date=December 14, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224815/http://pluto.jhuapl.edu/news_center/news/062807.php |archive-date=November 13, 2014 }}</ref> During hibernation mode, the onboard computer monitored the probe's systems and transmitted a signal back to Earth; a "green" code if everything was functioning as expected or a "red" code if mission control's assistance was needed.<ref name=hibernation1/> The probe was activated for about two months a year so that the instruments could be calibrated and the systems checked. The first hibernation mode cycle started on June 28, 2007,<ref name=hibernation1/> the second cycle began on December 16, 2008,<ref>[http://pluto.jhuapl.edu/news_center/news/121908.php New Horizons Earns a Holiday] {{webarchive|url=https://web.archive.org/web/20141113224845/http://pluto.jhuapl.edu/news_center/news/121908.php |date=November 13, 2014 }} JHUAPL December 19, 2008</ref> the third cycle on August 27, 2009,<ref>[http://pluto.jhuapl.edu/news_center/news/20090828.php New Horizons Checks Out, Enters Hibernation] {{webarchive|url=https://web.archive.org/web/20141113224816/http://pluto.jhuapl.edu/news_center/news/20090828.php |date=November 13, 2014 }} JHUAPL August 28, 2009</ref> and the fourth cycle on August 29, 2014, after a 10-week test.<ref>[http://pluto.jhuapl.edu/news_center/news/20140829.php New Horizons Commanded into Last Pre-Pluto Slumber] {{webarchive|url=https://web.archive.org/web/20141113224855/http://pluto.jhuapl.edu/news_center/news/20140829.php |date=November 13, 2014 }} JHUAPL August 29, 2014</ref>

''New Horizons'' crossed the orbit of [[Astronomy:Saturn|Saturn]] on June 8, 2008,<ref name=saturn>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/060808.php |title=New Horizons Ventures Beyond Saturn's Orbit |publisher=Johns Hopkins APL |date=2008 |access-date=December 14, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224829/http://pluto.jhuapl.edu/news_center/news/060808.php |archive-date=November 13, 2014 }}</ref> and [[Astronomy:Uranus|Uranus]] on March 18, 2011.<ref name=uranus>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/20110318.php |title=Later, Uranus: New Horizons Passes Another Planetary Milestone |publisher=Johns Hopkins APL |date=2011 |access-date=December 14, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224830/http://pluto.jhuapl.edu/news_center/news/20110318.php |archive-date=November 13, 2014 }}</ref> After astronomers announced the discovery of two new moons in the Pluto system, Kerberos and Styx, mission planners started contemplating the possibility of the probe running into unseen debris and dust left over from ancient collisions between the moons. A study based on 18 months of computer simulations, Earth-based telescope observations and occultations of the Pluto system revealed that the possibility of a catastrophic collision with debris or dust was less than 0.3% on the probe's scheduled course.<ref name=debris1>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/20121016.php |title=At Pluto, Moons and Debris May Be Hazardous to New Horizons |publisher=Johns Hopkins APL |date=2012 |access-date=December 14, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224823/http://pluto.jhuapl.edu/news_center/news/20121016.php |archive-date=November 13, 2014 }}</ref><ref name=debris2>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/20130614.php |title=New Horizons Team Sticking to Original Flight Plan at Pluto |publisher=Johns Hopkins APL |date=2013 |access-date=December 14, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224851/http://pluto.jhuapl.edu/news_center/news/20130614.php |archive-date=November 13, 2014 }}</ref> If the hazard increased, ''New Horizons'' could have used one of two possible contingency plans, the so-called SHBOTs (Safe Haven by Other Trajectories). Either the probe could have continued on its present trajectory with the antenna facing the incoming particles so the more vital systems would be protected, or it could have positioned its antenna to make a course correction that would take it just 3000&nbsp;km from the surface of Pluto where it was expected that the atmospheric drag would have cleaned the surrounding space of possible debris.<ref name=debris2/>

While in hibernation mode in July 2012, ''New Horizons'' started gathering scientific data with SWAP, PEPSSI and VBSDC. Although it was originally planned to activate just the VBSDC, other instruments were powered on in order to collect valuable heliospheric data. Before activating the other two instruments, ground tests were conducted to make sure that the expanded data gathering in this phase of the mission would not limit available energy, memory and fuel in the future and that all systems were functioning during the flyby.<ref name=new_instruments>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/20120709.php |title=New Horizons Doing Science in Its Sleep |publisher=Johns Hopkins APL |date=2012 |access-date=December 14, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224851/http://pluto.jhuapl.edu/news_center/news/20120709.php |archive-date=November 13, 2014 }}</ref> The first set of data was transmitted in January 2013 during a three-week activation from hibernation. The command and data handling software was updated to address the problem of computer resets.<ref name=data>{{cite web |url=http://pluto.jhuapl.edu/news_center/news/20130110.php |title=New Horizons Gets a New Year's Workout |publisher=Johns Hopkins APL |date=2013 |access-date=December 14, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113224830/http://pluto.jhuapl.edu/news_center/news/20130110.php |archive-date=November 13, 2014 }}</ref>

==== Possible Neptune trojan targets ====
Other possible targets were [[Astronomy:Neptune trojan|Neptune trojan]]s. The probe's trajectory to Pluto passed near Neptune's trailing [[Astronomy:Lagrangian point|Lagrange point]] ("{{L5}}"), which may host hundreds of bodies in 1:1 resonance. In late 2013, ''New Horizons'' passed within {{convert|1.2|AU|e6km e6mi|abbr=unit}} of the high-inclination L5 Neptune trojan {{mpl|2011 HM|102}},<ref name=parker2012>{{cite journal |last1=Parker |first1=Alex H. |display-authors=0 |title=2011 HM102: Discovery of a High-Inclination L5 Neptune Trojan in the Search for a post-Pluto New Horizons Target |journal=The Astronomical Journal |volume=145 |issue=4 |page=96 |date=2013 |arxiv=1210.4549 |bibcode=2013AJ....145...96P |doi=10.1088/0004-6256/145/4/96|s2cid=119267735 }}</ref> which was discovered shortly before by the New Horizons KBO Search task, a [[Astronomy:Astronomical survey|survey]] to find additional [[Astronomy:Distant minor planet|distant objects]] for ''New Horizons'' to fly by after its 2015 encounter with Pluto. At that range, {{mp|2011 HM|102}} would have been bright enough to be detectable by ''New Horizons''{{'}} LORRI instrument; however, the ''New Horizons'' team eventually decided that they would not target {{mp|2011 HM|102}} for observations because the preparations for the Pluto approach took precedence.<ref>{{cite news |last=Parker |first=Alex |url=http://www.planetary.org/blogs/guest-blogs/2013/0430-2011hm102-new-neptune-companion.html |title=2011 HM102: A new companion for Neptune |work=The Planetary Society |date=April 30, 2013 |access-date=October 7, 2014 |archive-date=October 9, 2014 |archive-url=https://web.archive.org/web/20141009183627/http://www.planetary.org/blogs/guest-blogs/2013/0430-2011hm102-new-neptune-companion.html |url-status=live }}</ref> On August 25, 2014, ''New Horizons'' crossed the orbit of [[Astronomy:Neptune|Neptune]], exactly 25 years after the planet was visited by the ''[[Astronomy:Voyager 2|Voyager 2]]'' probe.<ref>{{cite news |last=Northon |first=Karen |url=https://www.nasa.gov/press/2014/august/nasa-s-new-horizons-spacecraft-crosses-neptune-orbit-en-route-to-historic-pluto |title=NASA's New Horizons Spacecraft Crosses Neptune Orbit En Route to Historic Pluto Encounter |work=NASA |date=August 25, 2014 |access-date=July 26, 2023 }}</ref> This was the last major planet orbit crossing before the Pluto flyby. At the time, the spacecraft was {{convert|3.99|e9km|e9mi AU|abbr=unit}} away from Neptune and {{convert|4.51|e9km|e9mi AU|abbr=unit}} from the Sun.

==== Observations of Pluto and Charon 2013–14 ====
Images from July 1 to 3, 2013, by LORRI were the first by the probe to resolve Pluto and Charon as separate objects.<ref>{{cite news |last=Atkinson |first=Nancy |url=http://www.universetoday.com/103429/new-horizons-i-spy-pluto-and-charon/ |title=New Horizons: I Spy Pluto and Charon! |work=Universe Today |date=July 10, 2013 |access-date=October 7, 2014}}</ref> On July 14, 2014, mission controllers performed a sixth trajectory-correction maneuver (TCM) since its launch to enable the craft to reach Pluto.<ref>[http://pluto.jhuapl.edu/news_center/news/20140715.php New Horizons Marks a 'Year Out' with a Successful Course Correction] {{webarchive|url=https://web.archive.org/web/20141113224821/http://pluto.jhuapl.edu/news_center/news/20140715.php |date=November 13, 2014 }}, New Horizons NASA July 17, 2014</ref> Between July 19–24, 2014, ''New Horizons''{{'}} LORRI snapped 12 images of Charon revolving around Pluto, covering almost one full rotation at distances ranging from about {{convert|429|to|422|e6km|e6mi|abbr=unit|sp=us}}.<ref>{{cite web |url=http://pluto.jhuapl.edu/Multimedia/Science-Photos/pics/PR_E12_proper_nosat_3fps.png |title=A Moon over Pluto (Close up) |date=August 7, 2014 |publisher=Johns Hopkins APL |access-date=February 11, 2015 |archive-url=https://web.archive.org/web/20160826101411/http://pluto.jhuapl.edu/Multimedia/Science-Photos/pics/PR_E12_proper_nosat_3fps.png |archive-date=August 26, 2016 |url-status=dead }}</ref> In August 2014, astronomers made high-precision measurements of Pluto's location and orbit around the Sun using the Atacama Large Millimeter/submillimeter Array ([[Astronomy:Atacama Large Millimeter Array|ALMA]]), an array of radio telescopes located in Chile, to help NASA's ''New Horizons'' spacecraft accurately home in on Pluto.<ref>{{cite news |title=ALMA Pinpoints Pluto to Help Guide New Horizons Spacecraft |url=http://www.eso.org/public/announcements/ann14059/ |access-date=August 7, 2014 |work=ESO Announcement}}</ref> On December 6, 2014, mission controllers sent a signal for the craft to "wake up" from its final Pluto-approach hibernation and begin regular operations. The craft's response that it was "awake" reached Earth on December 7, 2014, at 02:30&nbsp;UTC.<ref name="awoketwitter">{{cite web |url=https://twitter.com/NASANewHorizons |title=NASA New Horizons (@NASANewHorizons) – Twitter}}</ref><ref name="awokeAST">{{cite journal |last1=Nally |first1=Jonathan |title=Ready for a Close Encounter |journal=Australian Sky & Telescope |issue=83 |page=14 |issn=1832-0457}}</ref><ref>{{cite news |url=https://www.nbcnews.com/science/space/its-alive-nasas-new-horizons-pluto-probe-wakes-work-n262996 |title=It's Alive! NASA's New Horizons Pluto Probe 'Wakes Up' for Work |work=NBC News |date=December 6, 2014}}</ref>

=== Pluto approach ===
{{multiple image |direction=horizontal |align=right |total_width=300
 |image1=PlutoCharon-1stColorImage-NewHorizons-Ralph-20150409.png
 |image2=Pluto-System-June-29.png
 |footer=[[Astronomy:Pluto|Pluto]] and [[Astronomy:Charon (moon)|Charon]] photographed on April 9, 2015, ''(left)'' by [[Astronomy:Ralph (New Horizons)|Ralph]] and on June 29, 2015, ''(right)'' by [[Astronomy:Long Range Reconnaissance Imager|LORRI]].
}}
Distant-encounter operations at Pluto began on January 4, 2015.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20140829 |title=New Horizons Commanded into Last Pre-Pluto Slumber |publisher=Applied Physics Laboratory |date=August 29, 2014 |access-date=October 7, 2014}}</ref> On this date, images of the targets with the onboard LORRI imager plus the Ralph telescope were only a few [[Pixel|pixel]]s in width. Investigators began taking Pluto images and background starfield images to assist mission navigators in the design of course-correcting engine maneuvers that would precisely modify the trajectory of ''New Horizons'' to aim the approach.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150115 |title=New Horizons Begins First Stages of Pluto Encounter |publisher=Applied Physics Laboratory |date=January 15, 2015 |access-date=November 5, 2016 |archive-date=July 14, 2015 |archive-url=https://web.archive.org/web/20150714232102/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150115 |url-status=live }}</ref>

On February 12, 2015, NASA released new images of Pluto (taken from January 25 to 31) from the approaching probe.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150204 |title=Happy Birthday Clyde Tombaugh: New Horizons Returns New Images of Pluto |publisher=Applied Physics Laboratory |date=February 4, 2015 |access-date=November 5, 2016 |archive-date=July 14, 2015 |archive-url=https://web.archive.org/web/20150714231810/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150204 |url-status=live }}</ref><ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150212 |title=The View from New Horizons: A Full Day on Pluto-Charon |publisher=Applied Physics Laboratory |date=February 12, 2015 |access-date=November 5, 2016 |archive-date=July 14, 2015 |archive-url=https://web.archive.org/web/20150714133648/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150212 |url-status=live }}</ref> ''New Horizons'' was more than {{convert|203|e6km|e6mi|abbr=unit|sp=us}} away from Pluto when it began taking the photos, which showed Pluto and its largest moon, Charon. The exposure time was too short to see Pluto's smaller, much fainter moons.

Investigators compiled a series of images of the moons Nix and Hydra taken from January 27 through February 8, 2015, beginning at a range of {{convert|201|e6km|e6mi|abbr=unit|sp=us}}.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150218 |title=85 Years after Pluto's Discovery, New Horizons Spots Small Moons Orbiting Pluto |publisher=Applied Physics Laboratory |date=February 18, 2015 |access-date=November 5, 2016 |archive-date=July 14, 2015 |archive-url=https://web.archive.org/web/20150714232053/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150218 |url-status=live }}</ref> Pluto and Charon appear as a single overexposed object at the center. The right side image has been processed to remove the background starfield. The other two, even smaller moons—Kerberos and Styx—were seen on photos taken on April 25.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150512 |title=New Horizons Spots Pluto's Faintest Known Moons |publisher=Applied Physics Laboratory |date=May 12, 2015 |access-date=November 5, 2016 |archive-date=July 12, 2015 |archive-url=https://archive.today/20150712141848/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150512 |url-status=live }}</ref> Starting on May 11, a hazard search was performed, looking for unknown objects that could be a danger to the spacecraft, such as rings or hitherto undiscovered moons, which could then possibly be avoided by a course change.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150528 |title=So Far, All Clear: New Horizons Team Completes First Search for Pluto System Hazards |publisher=Applied Physics Laboratory |date=May 28, 2015 |access-date=November 5, 2016 |archive-date=July 14, 2015 |archive-url=https://web.archive.org/web/20150714232040/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150528 |url-status=live }}</ref> No rings or additional moons were found.

Also in regard to the approach phase during January 2015, on August 21, 2012, the team announced that they would spend mission time attempting long-range observations of the Kuiper belt object temporarily designated VNH0004 (now designated {{mpl|2011 KW|48}}), when the object was at a distance of {{convert|75|e6km|AU e6mi|abbr=unit|sp=us}} from ''New Horizons''.<ref name="vnh"/> The object would be too distant to resolve surface features or take spectroscopy, but it would be able to make observations that cannot be made from Earth, namely a [[Physics:Phase curve|phase curve]] and a search for small moons. A second object was planned to be observed in June 2015, and a third in September after the flyby; the team hoped to observe a dozen such objects through 2018.<ref name="vnh">{{cite news |url=http://www.americaspace.com/?p=24691 |title=New Horizons to Encounter KBO Ahead of Pluto Flyby |website=Americaspace.com |date=2012 |access-date=April 22, 2014 |archive-date=June 29, 2015 |archive-url=https://web.archive.org/web/20150629191044/http://www.americaspace.com/?p=24691 |url-status=live }}</ref> On April 15, 2015, Pluto was imaged showing a possible polar cap.<ref name="NASA-20150429">{{cite web |last1=Brown |first1=Dwayne |last2=Buckley |first2=Michael |title=NASA's New Horizons Detects Surface Features, Possible Polar Cap on Pluto |url=http://www.nasa.gov/press-release/nasa-s-new-horizons-detects-surface-features-possible-polar-cap-on-pluto |date=April 29, 2015 |publisher=[[Organization:NASA|NASA]] |access-date=April 30, 2015 |archive-date=July 5, 2015 |archive-url=https://web.archive.org/web/20150705011700/http://www.nasa.gov/press-release/nasa-s-new-horizons-detects-surface-features-possible-polar-cap-on-pluto/ |url-status=live }}</ref>

==== Software glitch ====
On July 4, 2015, ''New Horizons'' experienced a software anomaly and went into safe mode, preventing the spacecraft from performing scientific observations until engineers could resolve the problem.<ref>{{cite web |last1=Gipson |first1=Lillian |title=New Horizons Team Responds to Spacecraft Anomaly |url=http://www.nasa.gov/nh/new-horizons-responds-spacecraft-anomaly |publisher=[[Organization:NASA|NASA]] |date=July 4, 2015 |access-date=July 5, 2015 |archive-date=July 15, 2015 |archive-url=https://web.archive.org/web/20150715222035/http://www.nasa.gov/nh/new-horizons-responds-spacecraft-anomaly/ |url-status=live }}</ref><ref>{{cite news |author=Klotz, Irene |url=https://www.reuters.com/article/us-space-pluto-idUSKCN0PF0HW20150705 |title=New Horizons space probe suffers glitch on approach to Pluto |agency={{wipe|Reuters}} |date=July 5, 2015|newspaper=Reuters }}</ref> On July 5, NASA announced that the problem was determined to be a timing flaw in a command sequence used to prepare the spacecraft for its flyby, and the spacecraft would resume scheduled science operations on July 7. The science observations lost because of the anomaly were judged to have no impact on the mission's main objectives and minimal impact on other objectives.<ref name="NASA-new-horizons-2015-07-05">{{cite web |title=NASA's New Horizons Plans July 7 Return to Normal Science Operations |url=http://www.nasa.gov/nh/new-horizons-plans-july-7-return-to-normal-science-operations |website=NASA.gov |publisher=[[Organization:NASA|NASA]] |date=July 5, 2015 |access-date=July 6, 2015 |archive-date=July 6, 2015 |archive-url=https://web.archive.org/web/20150706043056/http://www.nasa.gov/nh/new-horizons-plans-july-7-return-to-normal-science-operations/ |url-status=live }}</ref>

The timing flaw consisted of performing two tasks simultaneously—compressing previously acquired data to release space for more data, and making a second copy of the approach command sequence—that together overloaded the spacecraft's primary computer. After the overload was detected, the spacecraft performed as designed: it switched from the primary computer to the backup computer, entered safe mode, and sent a distress call back to Earth. The distress call was received the afternoon of July 4 and alerted engineers that they needed to contact the spacecraft to get more information and resolve the issue. The resolution was that the problem happened as part of preparations for the approach, and was not expected to happen again because no similar tasks were planned for the remainder of the encounter.<ref name="NASA-new-horizons-2015-07-05"/><ref>{{cite news |last=Feltman |first=Rachel |title=New Horizons computer overload won't hurt the mission to Pluto, NASA says |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2015/07/06/after-a-heart-stopping-glitch-nasas-new-horizons-prepares-for-its-historic-pluto-flyby/ |newspaper={{wipe|The Washington Post}} |date=July 6, 2015}}</ref>

== Pluto system encounter ==
[[File:Alan Stern and New Horizons Team Celebrate Pluto Flyby.jpg|thumb|right|Alan Stern and the ''New Horizons'' team celebrate after the spacecraft successfully completed its flyby of Pluto.]]
The closest approach of the ''New Horizons'' spacecraft to Pluto occurred at 11:49&nbsp;UTC on July 14, 2015, at a range of {{convert|12472|km|mi|abbr=on}} from the surface<ref>{{cite web |title=NASA's Three-Billion-Mile Journey to Pluto Reaches Historic Encounter |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150714-2 |publisher=Johns Hopkins University Applied Physics Laboratory |date=July 14, 2015}}</ref> and {{convert|13658|km|mi|abbr=on}} from the center of Pluto. [[Telemetry]] data confirming a successful flyby and a healthy spacecraft was received on Earth from the vicinity of the Pluto system on July 15, 2015, 00:52:37&nbsp;UTC,<ref>{{cite web |author=Lakdawalla, Emily |title=New Horizons "phones home" after Pluto flyby |url=http://www.planetary.org/blogs/emily-lakdawalla/2015/07142231-new-horizons-phones-home.html |publisher=[[Organization:The Planetary Society|The Planetary Society]] |date=July 15, 2015}}</ref> after 22 hours of planned [[Social:Radio silence#Non-military radio silence|radio silence]] due to the spacecraft being pointed towards the [[Astronomy:Moons of Pluto|Pluto system]]. Mission managers estimated a one in 10,000 chance that debris could have destroyed the probe or its communication-systems during the flyby, preventing it from sending data to Earth.<ref>{{cite news |author=Phipps, Claire |title=Pluto: New Horizons probe makes contact with Earth |url=https://www.theguardian.com/science/2015/jul/15/new-horizons-pluto-probe-makes-contact-with-earth |newspaper={{wipe|The Guardian}} |date=July 15, 2015}}</ref> The first details of the encounter were received the next day, but the download of the complete data set through the 2 kbps data downlink took just over 15 months,<ref name="NYT-20161028" /> and analysis of the data continues as of 2021.<ref>{{Cite web|title=New Horizons: Using "Charon-light," Researchers Capture Pluto's Dark Side|url=http://pluto.jhuapl.edu/News-Center/PI-Perspectives.php?page=piPerspective_12_17_2021|access-date=2022-01-21|website=pluto.jhuapl.edu}}</ref>

=== Objectives ===
The mission's science objectives were grouped in three distinct priorities. The "primary objectives" were required. The "secondary objectives" were expected to be met but were not demanded. The "tertiary objectives" were desired. These objectives could have been skipped in favor of the above objectives. An objective to measure any magnetic field of Pluto was dropped, due to mass and budget issues associated with including a [[Physics:Magnetometer|magnetometer]] on the spacecraft. Instead, SWAP and PEPSSI could indirectly detect magnetic fields around Pluto.<ref>{{cite book |last1=Jones |first1=Barrie W. |url=https://books.google.com/books?id=8nKZnNnWjE0C&pg=PA189 |title=Pluto: Sentinel of the Outer Solar System |publisher=Cambridge University Press |year=2010 |page=189 |isbn=9781139490221 |access-date=May 1, 2018}}</ref>

* '''Primary objectives (required)'''
** Characterize the global geology and morphology of Pluto and Charon
** Map chemical compositions of Pluto and Charon surfaces
** Characterize the neutral (non-[[Physics:Ion|ion]]ized) [[Astronomy:Atmosphere of Pluto|atmosphere of Pluto]] and its escape rate
* '''Secondary objectives (expected)'''
** Characterize the time variability of Pluto's surface and atmosphere
** Image select Pluto and Charon areas in [[Stereoscopy|stereo]]
** Map the [[Astronomy:Terminator (solar)|terminators]] (day/night border) of Pluto and Charon with high resolution
** Map the chemical compositions of select Pluto and Charon areas with high resolution
** Characterize Pluto's [[Astronomy:Ionosphere|ionosphere]] (upper layer of the atmosphere) and its interaction with the [[Astronomy:Solar wind|solar wind]]
** Search for molecular neutral species such as molecular hydrogen, [[Chemistry:Hydrocarbon|hydrocarbon]]s, [[Chemistry:Hydrogen cyanide|hydrogen cyanide]] and other [[Chemistry:Nitrile|nitrile]]s in the atmosphere
** Search for any Charon atmosphere
** Determine bolometric [[Physics:Bond albedo|Bond albedo]]s for Pluto and Charon
** Map surface temperatures of Pluto and Charon
** Map any additional surfaces of outermost moons: Nix, Hydra, Kerberos, and Styx
* '''Tertiary objectives (desired)'''
** Characterize the energetic particle environment at Pluto and Charon
** Refine bulk parameters (radii, masses) and orbits of Pluto and Charon
** Search for additional [[Astronomy:Natural satellite|moons]] and any rings

"The New Horizons flyby of the Pluto system was fully successful, meeting and in many cases exceeding, the Pluto objectives set out for it by NASA and the National Academy of Sciences."<ref>{{cite journal |title=The New Horizons Kuiper Belt Extended Mission |journal=S.A. Stern, H.A. Weaver, J.R. Spencer, H.A. Elliott, the New Horizons Team |year=2018 |page=4 |doi=10.1007/s11214-018-0507-4 |arxiv=1806.08393 |last1=Stern |first1=S. A. |last2=Weaver |first2=H. A. |last3=Spencer |first3=J. R. |last4=Elliott |first4=H. A. |author5=the New Horizons Team |volume=214 |issue=4 |bibcode=2018SSRv..214...77S |s2cid=119506499 }}</ref>

=== Flyby details ===
{{multiple image |direction=horizontal |align=right |total_width=300
 |image1=Pluto in True Color - High-Res.jpg |caption1=Pluto's "encounter hemisphere" viewed by ''New Horizons'' on July 14, 2015
 |image2=Pluto by LORRI, 11 July 2015.jpg |caption2=Pluto's Charon-facing opposing hemisphere viewed on July 11, 2015
}}
[[File:New Horizons flyby of Pluto (Eyes on the Solar System).ogg|thumb|Animation of ''New Horizons''{{'}} flyby of Pluto in [[Software:NASA's Eyes|Eyes on the Solar System]].]]
''New Horizons'' passed within {{cvt|12500|km|mi}} of Pluto, with this closest approach on July 14, 2015, at 11:50&nbsp;UTC. ''New Horizons'' had a relative velocity of {{cvt|13.78|km/s|km/h mph}} at its closest approach, and came as close as {{cvt|28800|km|mi}} to Charon. Starting 3.2 days before the closest approach, long-range imaging included the mapping of Pluto and Charon to {{cvt|40|km|mi}} resolution. This is half the rotation period of the Pluto–Charon system and allowed imaging of all sides of both bodies. Close range imaging was repeated twice per day in order to search for surface changes caused by localized snow fall or surface cryovolcanism. Because of Pluto's tilt, a portion of the northern hemisphere would be in shadow at all times. During the flyby, engineers expected LORRI to be able to obtain select images with resolution as high as {{cvt|50|m|ft|disp=x| per pixel (|/px)}} if closest distance were around {{cvt|12500|km|mi}}, and MVIC was expected to obtain four-color global dayside maps at {{cvt|1.6|km|mi|0}} resolution. LORRI and MVIC attempted to overlap their respective coverage areas to form stereo pairs. LEISA obtained hyperspectral near-infrared maps at {{cvt|7|km|mi|disp=x|/px (|/px)}} globally and {{cvt|0.6|km|mi|disp=x|/px (|/px)}} for selected areas.

[[File:Snakeskin terrain on Pluto (PIA19957).png|thumb|left|Patterns of blue-gray ridges and reddish material observed in the Tartarus Dorsa region on July 14, 2015]]

Meanwhile, Alice characterized the atmosphere, both by emissions of atmospheric molecules ([[Astronomy:Airglow|airglow]]), and by dimming of background stars as they pass behind Pluto ([[Astronomy:Occultation|occultation]]). During and after closest approach, SWAP and PEPSSI sampled the high atmosphere and its effects on the solar wind. VBSDC searched for dust, inferring meteoroid collision rates and any invisible rings. REX performed active and passive radio science. The communications dish on Earth measured the disappearance and reappearance of the [[Astronomy:Radio occultation|radio occultation]] signal as the probe flew by behind Pluto. The results resolved Pluto's diameter (by their timing) and atmospheric density and composition (by their weakening and strengthening pattern). (Alice can perform similar occultations, using sunlight instead of radio beacons.) Previous missions had the spacecraft transmit through the atmosphere, to Earth ("downlink"). Pluto's mass and mass distribution were evaluated by the gravitational tug on the spacecraft. As the spacecraft speeds up and slows down, the radio signal exhibited a Doppler shift. The Doppler shift was measured by comparison with the ultrastable oscillator in the communications electronics.

Reflected sunlight from Charon allowed some imaging observations of the nightside. Backlighting by the Sun gave an opportunity to highlight any rings or atmospheric hazes. REX performed radiometry of the nightside.
{{Clear}}

=== Satellite observations ===
''New Horizons''{{'}} best spatial resolution of the small satellites is {{cvt|330|m|ft|disp=x| per pixel (|/px)}} at Nix, {{cvt|780|m|ft|disp=x|/px (|/px)}} at Hydra, and approximately {{cvt|1.8|km|mi|disp=x|/px (|/px)}} at Kerberos and Styx. Estimates for the dimensions of these bodies are: Nix at {{cvt|49.8|xx|33.2|xx|31.1|km|mi}}; Hydra at {{cvt|50.9|xx|36.1|xx|30.9|km|mi}}; Kerberos at {{cvt|19|xx|10|xx|9|km|mi}}; and Styx at {{cvt|16|xx|9|xx|8|km|mi}}.<ref name="phasecurves">{{cite journal |last1=Verbiscer |first1=A. J. |last2=Porter |first2=S. B. |last3=Buratti |first3=B. J. |last4=Weaver |first4=H. A. |last5=Spencer |first5=J. R. |last6=Showalter |first6=M. R. |last7=Buie |first7=M. W. |last8=Hofgartner |first8=J. D. |last9=Hicks |first9=M. D. |last10=Ennico-Smith |first10=K. |last11=Olkin |first11=C. B. |last12=Stern |first12=S. A. |last13=Young |first13=L. A. |last14=Cheng |first14=A. |title=Phase Curves of Nix and Hydra from the ''New Horizons'' Imaging Cameras |journal=The Astrophysical Journal |date=2018 |volume=852 |issue=2 |pages=L35 |doi=10.3847/2041-8213/aaa486|doi-access=free |bibcode=2018ApJ...852L..35V }}</ref>

Initial predictions envisioned Kerberos as a relatively large and massive object whose dark surface led to it having a faint reflection. This proved to be wrong as images obtained by ''New Horizons'' on July 14 and sent back to Earth in October 2015 revealed that Kerberos was smaller in size, {{cvt|19|km|mi}} across with a highly reflective surface suggesting the presence of relatively clean water ice similarly to the rest of Pluto's smaller moons.<ref name=kerberos>{{cite web |url=http://www.astronomy.com/news/2015/10/last-of-plutos-moons--mysterious-kerberos--revealed-by-new-horizons |title=Last of Pluto's moons – mysterious Kerberos – revealed by New Horizons |work=[[Astronomy:Astronomy (magazine)|Astronomy.com]] |date=October 23, 2015 |access-date=December 6, 2015}}</ref>

{{Multiple image |align=center |total_width=800
 |header=Satellites of Pluto imaged by ''New Horizons''
 |image1=Charon in True Color - High-Res.jpg |caption1=[[Astronomy:Charon (moon)|Charon]]
 |image2=Styx (moon).jpg |caption2=Styx
 |image3=Nix best view.jpg |caption3=Nix
 |image4=Kerberos (moon).jpg |caption4=Kerberos
 |image5=Hydra Enhanced Color.jpg |caption5=Hydra
}}

== Post-Pluto events ==
[[File:Blue hazes over backlit Pluto.jpg|thumb|left|View of Pluto as ''New Horizons'' left the system, catching the Sun's rays passing through Pluto's atmosphere, forming a ring]]
Soon after the Pluto flyby, in July 2015, ''New Horizons'' reported that the spacecraft was healthy, its flight path was within the margins, and science data of the Pluto–Charon system had been recorded.<ref name="NYT-20150714-kc2">{{cite news |url=https://www.nytimes.com/2015/07/15/science/space/nasa-new-horizons-spacecraft-reaches-pluto.html |title=NASA's New Horizons Spacecraft Sends Signal From Pluto to Earth |work={{wipe|The New York Times}} |last=Chang |first=Kenneth |date=July 14, 2015 |access-date=July 14, 2015 |archive-date=January 18, 2018 |archive-url=https://web.archive.org/web/20180118163357/https://www.nytimes.com/2015/07/15/science/space/nasa-new-horizons-spacecraft-reaches-pluto.html |url-status=live }}</ref><ref>{{cite news |url=https://www.nbcnews.com/science/space/nasas-new-horizons-probe-phones-home-after-pluto-flyby-n391611 |title=NASA's New Horizons Probe Phones Home After Historic Pluto Flyby |work=NBC News |first=Alan |last=Boyle |date=July 14, 2015 |access-date=July 14, 2015}}</ref> The spacecraft's immediate task was to begin returning the 6.25 gigabytes of information collected.<ref name="NYT-20161028" /> The [[Physics:Free-space path loss|free-space path loss]] at its distance of 4.5&nbsp;light-hours ({{Convert|3|e9km|AU e9mi|abbr=unit|disp=or}}) is approximately 303&nbsp;[[Physics:Decibel|dB]] at 7&nbsp;GHz. Using the high gain antenna and transmitting at full power, the signal from EIRP is +83 dBm, and at this distance, the signal reaching Earth is −220 dBm. The received signal level (RSL) using one, un-arrayed Deep Space Network antenna with 72 dBi of forward gain equals −148 dBm.<ref>{{cite web | url=http://planetfox.net/microwaves/bandwidth.html | title=How Much Bandwidth Does a Satellite Have &#124; Microwaves &#124; Planet Fox}}</ref> Because of the extremely low RSL, it could only transmit data at 1 to 2 kilobits per second.<ref name="jhuhub20150717">{{cite web |url=http://hub.jhu.edu/2015/07/17/new-horizons-data-transmission/ |title=How exactly does New Horizons send all that data back from Pluto? |work=The Hub |publisher=Johns Hopkins University |first=Greg |last=Rienzi |date=July 17, 2015 |access-date=July 17, 2015}}</ref>

By March 30, 2016, about nine months after the flyby, ''New Horizons'' reached the halfway point of transmitting this data.<ref name="airspace20160330">{{cite news |url=http://www.airspacemag.com/daily-planet/new-horizons-still-only-halfway-through-its-download-pluto-180958617/ |title=New Horizons is Still Only Halfway Through Its Download from Pluto |work=Air & Space/Smithsonian |first=Kiona |last=Smith-Strickland |date=March 30, 2016 |access-date=November 5, 2016}}</ref> The transfer was completed on October 25, 2016, at 21:48&nbsp;UTC, when the last piece of data—part of a Pluto–Charon observation sequence by the Ralph/LEISA imager—was received by the Johns Hopkins University [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]].<ref name="NYT-20161028" /><ref name="nasa20161027">{{cite news |url=http://www.nasa.gov/feature/new-horizons-returns-last-bits-of-2015-flyby-data-to-earth |title=New Horizons Returns Last Bits of 2015 Flyby Data to Earth |publisher=NASA |editor-first=Tricia |editor-last=Talbert |date=October 27, 2016 |access-date=October 27, 2016 |archive-date=October 28, 2016 |archive-url=https://web.archive.org/web/20161028152315/http://www.nasa.gov/feature/new-horizons-returns-last-bits-of-2015-flyby-data-to-earth/ |url-status=live }}</ref>

As of November 2018, at a distance of {{convert|43|AU|e9km+e9mi|2|abbr=unit}} from the Sun and {{convert|0.4|AU|e6km+e6mi|abbr=unit}} from 486958 Arrokoth,<ref name="currentposition">{{cite web |url=http://pluto.jhuapl.edu/Mission/Where-is-New-Horizons/index.php |title=New Horizons Current Position |publisher=[[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] |access-date=November 26, 2018 |archive-date=May 9, 2015 |archive-url=https://web.archive.org/web/20150509174048/http://pluto.jhuapl.edu/Mission/Where-is-New-Horizons/index.php |url-status=live }}</ref> ''New Horizons'' was [[commons:File:New Horizons Full Trajectory.svg|heading in the direction]] of the constellation [[Astronomy:Sagittarius (constellation)|Sagittarius]]<ref name="heavens-escaping" /> at {{cvt|14.10|km/s|mi/s AU/year|lk=on}} relative to the Sun.<ref name="currentposition" /> The brightness of the Sun from the spacecraft was [[Astronomy:Magnitude|magnitude]] −18.5.<ref name="heavens-escaping">{{cite web |url=http://www.heavens-above.com/SolarEscape.aspx |title=Spacecraft escaping the Solar System |work=Heavens-Above |last=Peat |first=Chris |access-date=November 26, 2018 |archive-date=May 11, 2018 |archive-url=https://web.archive.org/web/20180511013456/http://www.heavens-above.com/SolarEscape.aspx |url-status=live }}</ref>

On April 17, 2021, ''New Horizons'' reached a distance of 50&nbsp;AU from the Sun, while remaining fully operational.<ref>{{cite news |title=After Visiting Pluto, NASA's New Horizons Spacecraft Reaches Another Cosmic Milestone |url=https://time.com/5955695/new-horizons-50-au/ |date=April 16, 2021 |magazine=TIME|accessdate=April 18, 2021 }}</ref>

{{clear}}

== Mission extension ==
[[File:Oort cloud Sedna orbit.svg|thumb|Big picture: from the inner Solar System to the Oort cloud with the Kuiper belt in between]]

The ''New Horizons'' team requested, and received, a mission extension through 2021 to explore additional Kuiper belt objects (KBOs). Funding was secured on July 1, 2016.<ref name="Mission Extension"/> During this Kuiper Belt Extended Mission (KEM) the spacecraft performed a close fly-by of [[Astronomy:486958 Arrokoth|486958 Arrokoth]] and will conduct more distant observations of an additional two dozen objects,<ref name="extension request">{{cite news |url=http://www.space.com/32660-new-horizons-extended-mission-kuiper-belt.html |title=New Horizons Encore? Pluto Probe's Team Proposes Extension |work=Space.com |last=Wall |first=Mike |date=April 25, 2016 |access-date=April 27, 2016}}</ref><ref name="Mission Extension">{{cite news |url=http://www.space.com/33332-new-horizons-pluto-probe-mission-extension.html |title=It's Official! NASA Pluto Probe to Fly by Another Object in 2019 |work=Space.com |last=Wall |first=Mike |date=July 1, 2016 |access-date=July 3, 2016}}</ref><ref name="verge20160701">{{cite news |url=https://www.theverge.com/2016/7/1/11686404/nasa-new-horizons-mission-funding-extension-mu69 |title=NASA extends the New Horizons mission to fly by another small world beyond Pluto |work=The Verge |first=Loren |last=Grush |date=July 1, 2016 |access-date=September 11, 2016}}</ref> and possibly make a fly-by of another KBO.{{Citation needed|date=January 2019}}

=== Kuiper belt object mission ===

==== Target background ====
Mission planners searched for one or more additional Kuiper belt objects (KBOs) of the order of {{cvt|50|–|100|km|mi}} in diameter as targets for flybys similar to the spacecraft's Plutonian encounter. However, despite the large population of KBOs, many factors limited the number of possible targets. Because the flight path was determined by the Pluto flyby, and the probe only had 33 kilograms of [[Chemistry:Hydrazine|hydrazine]] [[Chemistry:Rocket propellant|propellant]] remaining, the object to be visited needed to be within a cone of less than a degree's width extending from Pluto. The target also needed to be within 55&nbsp;AU, because beyond 55&nbsp;AU, the communications link becomes too weak, and the RTG power output decays significantly enough to hinder observations.<ref>{{cite web|title=New Horizons conducts flyby of Pluto in historic Kuiper Belt encounter|author=Chris Gebhardt|publisher=NASA|year=2015|url=https://www.nasaspaceflight.com/2015/07/new-horizons-pluto-historic-kuiper-encounter/|access-date=2019-08-30}}</ref> Desirable KBOs are well over {{cvt|50|km|-1}} in diameter, neutral in color (to contrast with the reddish Pluto), and, if possible, have a moon that imparts a wobble.{{citation needed|date=January 2019}}

==== KBO Search ====
[[File:New Horizons KEM Trajectory.png|thumb|Trajectory of ''New Horizons'' and other nearby Kuiper belt objects]]
{{anchor|New Horizons KBO Search}}
In 2011, mission scientists started the '''New Horizons KBO Search''', a dedicated [[Astronomy:Astronomical survey|survey]] for suitable KBOs using ground telescopes. Large ground telescopes with wide-field cameras, notably the twin 6.5-meter [[Astronomy:Magellan Telescopes|Magellan Telescopes]] in Chile, the 8.2-meter [[Astronomy:Subaru Telescope|Subaru Observatory]] in Hawaii and the [[Astronomy:Canada–France–Hawaii Telescope|Canada–France–Hawaii Telescope]]<ref name=parker2012/><ref name="Pluto-bound probe faces crisis">[http://www.nature.com/news/pluto-bound-probe-faces-crisis-1.15261 Pluto-bound probe faces crisis] (nature.com May 20, 2014)</ref> were used to search for potential targets. By participating in a citizen-science project called Ice Hunters the public helped to scan telescopic images for possible suitable mission candidates.<ref name="icehunters">{{cite web |url=http://demo.icehunters.org/ |archive-url=https://web.archive.org/web/20140505003325/http://demo.icehunters.org/ |url-status=dead |archive-date=May 5, 2014 |title=IceHunters |publisher=Zooniverse |date=2011 |access-date=June 27, 2011}}</ref><ref name="icehuntersdone">{{cite web |url=https://www.zooniverse.org/project/icehunters |title=IceHunters project complete |publisher=Zooniverse |date=2012 |access-date=August 7, 2012}}</ref><ref>{{cite web |title=Ice Hunters web site |url=http://www.icehunters.org |publisher=Zooniverse.Org |access-date=July 8, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120721055846/http://www.icehunters.org/ |archive-date=July 21, 2012 }}</ref><ref name=nasaice>{{cite web |title=Citizen Scientists: Discover a New Horizons Flyby Target |url=http://solarsystem.nasa.gov/news/display.cfm?News_ID=37726 |publisher=[[Organization:NASA|NASA]] |access-date=August 23, 2011 |date=June 21, 2011 |archive-date=October 5, 2012 |archive-url=https://web.archive.org/web/20121005160611/http://solarsystem.nasa.gov/news/display.cfm?News_ID=37726 |url-status=dead }}</ref><ref name = "exciting">{{cite web |last=Lakdawalla |first=Emily |date=June 21, 2011 |title=The most exciting citizen science project ever (to me, anyway) |publisher=[[Organization:The Planetary Society|The Planetary Society]] |url=http://planetary.org/blog/article/00003073/ |access-date=August 31, 2011 |archive-date=June 14, 2012 |archive-url=https://web.archive.org/web/20120614040626/http://www.planetary.org/blogs/emily-lakdawalla/2011/3073.html |url-status=live }}</ref> The ground-based search resulted in the discovery of about 143 KBOs of potential interest,<ref>{{cite web |title=Confirmed KBOs |url=http://www.icehunters.org/catalogue.php?task=6&page=1 |website=New Horizons Ice Hunters |publisher=Zooniverse |access-date=August 21, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20141211123836/http://www.icehunters.org/catalogue.php?task=6&page=1 |archive-date=December 11, 2014}}</ref> but none of these were close enough to the flight path of ''New Horizons''.<ref name="Pluto-bound probe faces crisis"/> Only the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] was deemed likely to find a suitable target in time for a successful KBO mission.<ref name="witze20140520">{{cite news |url=http://www.scientificamerican.com/article/pluto-bound-spacecraft-faces-crisis/ |title=Pluto-Bound Spacecraft Faces Crisis |work=Nature |date=May 20, 2014 |access-date=May 26, 2014 |author=Witze, Alexandra}}</ref> On June 16, 2014, time on Hubble was granted for a search.<ref>{{cite web |url=http://www.nasaspaceflight.com/2014/06/hubble-recruited-new-horizons-pluto-target/ |title=Hubble recruited to find New Horizons probe post-Pluto target |work=nasaspaceflight.com|date=June 16, 2014 }}</ref> Hubble has a much greater ability to find suitable KBOs than ground telescopes. The probability that a target for ''New Horizons'' would be found was estimated beforehand at about 95%.<ref>[https://archive.today/20140625194129/http://www.spacenews.com/article/civil-space/40944hubble-to-lend-pluto-probe-helping-hand-in-search-for-secondary-target Hubble To Lend Pluto Probe Helping Hand in Search for Secondary Target] spacenews.com June 25, 2014.</ref>

==== Suitable KBOs ====
[[File:KBO 2014 MU69 HST.jpg|thumb|486958 Arrokoth, the announced target for the Kuiper belt object mission]]

On October 15, 2014, it was revealed that Hubble's search had uncovered three potential targets,<ref name="NASA-20141015">{{cite web |last1=Brown |first1=Dwayne |last2=Villard |first2=Ray |title=RELEASE 14-281 NASA's Hubble Telescope Finds Potential Kuiper Belt Targets for New Horizons Pluto Mission |url=http://www.nasa.gov/press/2014/october/nasa-s-hubble-telescope-finds-potential-kuiper-belt-targets-for-new-horizons |date=October 15, 2014 |work=[[Organization:NASA|NASA]] |access-date=October 16, 2014 |archive-date=April 6, 2020 |archive-url=https://web.archive.org/web/20200406132923/https://www.nasa.gov/press/2014/october/nasa-s-hubble-telescope-finds-potential-kuiper-belt-targets-for-new-horizons |url-status=live }}</ref><ref name = "Lakdawalla2014"/><ref>{{cite web |title=NASA's Hubble Telescope Finds Potential Kuiper Belt Targets for New Horizons Pluto Mission |work=press release |publisher=Johns Hopkins [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] |date=October 15, 2014 |access-date=October 16, 2014 |archive-date=October 16, 2014 |url=http://www.jhuapl.edu/newscenter/pressreleases/2014/141015_2.asp |archive-url=https://web.archive.org/web/20141016023345/http://www.jhuapl.edu/newscenter/pressreleases/2014/141015_2.asp}}</ref><ref name = "Wall2014">{{cite news |last=Wall |first=Mike |title=Hubble Telescope Spots Post-Pluto Targets for New Horizons Probe |work=Space.com |date=October 15, 2014 |access-date=October 15, 2014 |archive-date=October 15, 2014 |url=http://www.space.com/27445-hubble-telescope-new-horizons-kuiper-belt.html |archive-url=https://web.archive.org/web/20141015233156/http://www.space.com/27445-hubble-telescope-new-horizons-kuiper-belt.html}}</ref><ref>{{cite web |author=Buie, Marc |title=New Horizons HST KBO Search Results: Status Report |url=http://www.stsci.edu/institute/stuc/oct-2014/New-Horizons.pdf |publisher=[[Organization:Space Telescope Science Institute|Space Telescope Science Institute]] |date=October 15, 2014 |page=23 |access-date=May 10, 2015 |archive-date=July 27, 2015 |archive-url=https://wayback.archive-it.org/all/20150727213348/http://www.stsci.edu/institute/stuc/oct-2014/New-Horizons.pdf |url-status=dead }}</ref> temporarily designated PT1 ("potential target 1"), PT2 and PT3 by the ''New Horizons'' team. PT1 was eventually chosen as the target and would be named [[Astronomy:486958 Arrokoth|486958 Arrokoth]].

All objects had estimated diameters in the {{cvt|30|-|55|km|mi}} range and were too small to be seen by ground telescopes. The targets were at distances from the Sun ranging from 43 to 44&nbsp;AU, which would put the encounters in the 2018–2019 period.<ref name="Lakdawalla2014" /> The initial estimated probabilities that these objects were reachable within ''New Horizons''{{'}} fuel budget were 100%, 7%, and 97%, respectively.<ref name="Lakdawalla2014" /> All were members of the "cold" (low-[[Astronomy:Orbital inclination|inclination]], low-[[Astronomy:Orbital eccentricity|eccentricity]]) classical Kuiper belt objects, and thus were very different from Pluto.

[[Astronomy:486958 Arrokoth|PT1]] (given the temporary designation "1110113Y" on the HST web site<ref>{{cite web |title=Hubble to Proceed with Full Search for New Horizons Targets |work=HubbleSite news release |publisher=[[Organization:Space Telescope Science Institute|Space Telescope Science Institute]] |date=July 1, 2014 |access-date=October 15, 2014 |url=http://hubblesite.org/newscenter/archive/releases/2014/35/image/a/ |archive-date=May 12, 2015 |archive-url=https://web.archive.org/web/20150512031618/http://hubblesite.org/newscenter/archive/releases/2014/35/image/a/ |url-status=live }}</ref>), the most favorably situated object, had a magnitude of 26.8, is {{cvt|30|-|45|km|mi}} in diameter, and was encountered in January 2019.<ref name="VOX-20150414">{{cite web |last=Stromberg |first=Joseph |title=NASA's New Horizons probe is visiting Pluto – and just sent back its first color photos |url=https://www.vox.com/2015/4/14/8412031/pluto-new-horizons |date=April 14, 2015 |work=Vox |access-date=April 14, 2015 |archive-date=April 6, 2020 |archive-url=https://web.archive.org/web/20200406132908/https://www.vox.com/2015/4/14/8412031/pluto-new-horizons |url-status=live }}</ref> A course change to reach it required about 35% of ''New Horizons''{{'}} available [[Astronomy:Delta-v budget|trajectory-adjustment fuel supply]].  A mission to PT3 was in some ways preferable, in that it is brighter and therefore probably larger than PT1, but the greater fuel requirements to reach it would have left less for maneuvering and unforeseen events.<ref name="Lakdawalla2014">{{cite web |last=Lakdawalla |first=Emily |title=Finally! New Horizons has a second target |work=Planetary Society blog |publisher=Planetary Society |date=October 15, 2014 |access-date=October 15, 2014 |archive-date=October 15, 2014 |url=http://www.planetary.org/blogs/emily-lakdawalla/2014/10151024-finally-new-horizons-has-a-kbo.html |archive-url=https://web.archive.org/web/20141015230432/http://www.planetary.org/blogs/emily-lakdawalla/2014/10151024-finally-new-horizons-has-a-kbo.html |url-status=live}}</ref>

Once sufficient orbital information was provided, the [[Organization:Minor Planet Center|Minor Planet Center]] gave [[Astronomy:Provisional designation in astronomy|provisional designations]] to the three target KBOs: {{mpl|2014 MU|69}} (later 486958 Arrokoth) (PT1), {{mpl|2014 OS|393}} (PT2), and {{mpl|2014 PN|70}} (PT3). By the fall of 2014, a possible fourth target, {{mpl|2014 MT|69}}, had been eliminated by follow-up observations. PT2 was out of the running before the Pluto flyby.<ref>{{cite web |author=Corey S. Powell |title=Alan Stern on Pluto's Wonders, New Horizons' Lost Twin, and That Whole "Dwarf Planet" Thing |url=http://blogs.discovermagazine.com/outthere/2015/03/29/alan-stern-on-plutos-wonders/ |magazine=Discover |date=March 29, 2015 |access-date=May 7, 2015 |archive-date=November 16, 2019 |archive-url=https://web.archive.org/web/20191116104116/http://blogs.discovermagazine.com/outthere/2015/03/29/alan-stern-on-plutos-wonders/ |url-status=live }}</ref><ref>{{Cite web |url=http://www.hou.usra.edu/meetings/lpsc2015/pdf/1301.pdf |title=Orbits and Accessibility of Potential New Horizons KBO Encounter Targets |access-date=December 12, 2018 |archive-date=March 3, 2016 |archive-url=https://web.archive.org/web/20160303182211/http://www.hou.usra.edu/meetings/lpsc2015/pdf/1301.pdf |url-status=live }}</ref>

==== KBO selection ====
On August 28, 2015, 486958 Arrokoth (then known as {{mp|486958|2014 MU|69}} and nicknamed ''Ultima Thule'') (PT1) was chosen as the flyby target. The necessary course adjustment was performed with four engine firings between October 22 and November 4, 2015.<ref name=wired-20151104>{{cite news |url=https://www.wired.com/2015/11/how-nasa-is-steering-new-horizons-toward-a-tiny-space-rock-in-the-kuiper-belt/ |title=How NASA Is Steering New Horizons Toward a Tiny Space Rock in the Kuiper Belt |magazine=Wired |first=Nick |last=Stockton |date=November 4, 2015 |access-date=May 30, 2017}}</ref><ref>{{cite news |url=https://www.nasaspaceflight.com/2017/01/new-horizons-2019-kuiper-belt-encounter/ |title=New Horizons prepares for New Year's Day 2019 Kuiper Belt Object encounter |work=NASASpaceFlight.com |first=Chris |last=Gebhardt |date=January 3, 2017}}</ref> The flyby occurred on January 1, 2019, at 00:33 UTC.<ref>{{cite news |title=NASA's New Horizons Team Selects Potential Kuiper Belt Flyby Target |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150828 |publisher=Johns Hopkins University Applied Physics Laboratory |date=August 15, 2015}}</ref><ref>{{cite news |url=http://space.io9.com/new-horizons-locks-onto-next-target-lets-explore-the-k-1727298103 |title=New Horizons Locks Onto Next Target: Let's Explore the Kuiper Belt! |work=io9 |last=McKinnon |first=Mika |date=August 28, 2015}}</ref>

=== Observations of other KBOs ===

Aside from its flyby of 486958 Arrokoth, the extended mission for ''New Horizons'' calls for the spacecraft to conduct observations of, and look for ring systems around, between 25 and 35 different KBOs.<ref name="Porter2017">{{cite conference |url=https://www.youtube.com/watch?v=KqOfJ6p1JmQ&t=1h22m55s  |archive-url=https://ghostarchive.org/varchive/youtube/20211221/KqOfJ6p1JmQ |archive-date=2021-12-21 |url-status=live|title=Constraints on the Shapes and Rotational States of the Distant New Horizons Kuiper Belt Targets |conference=AGU Fall Meeting. December 11–15, 2017. New Orleans, Louisiana. |first1=Simon |last1=Porter |first2=Anne |last2=Verbiscer |first3=John |last3=Spencer |first4=Harold |last4=Weaver |first5=Marc |last5=Buie |first6=Susan |last6=Benecchi |first7=Catherine |last7=Olkin |first8=Alan |last8=Stern |display-authors=1 |at=1:22:55–1:36:00 |date=December 11, 2017 |id=P13F-07}}{{cbignore}}</ref> In addition, it will continue to study the gas, dust and plasma composition of the Kuiper belt before the mission extension ends in 2021.<ref name="extension request" /><ref name="verge20160701" />{{Update inline|date=June 2022}}

On November 2, 2015, ''New Horizons'' imaged KBO [[Astronomy:15810 Arawn|15810 Arawn]] with the LORRI instrument from {{convert|280|e6km|e6mi+AU|abbr=unit|disp=x| away (|)}}.<ref name="spdaily20151207">{{cite news |url=http://www.spacedaily.com/reports/New_Horizons_catches_a_wandering_Kuiper_Belt_Object_not_far_off_999.html |title=New Horizons' catches a wandering Kuiper Belt Object not far off |work=Space Daily |date=December 7, 2015 |access-date=December 19, 2015}}</ref> This KBO was again imaged by the LORRI instrument on April 7–8, 2016, from a distance of {{convert|111|e6km|e6mi+AU|abbr=unit}}. The new images allowed the science team to further refine the location of 15810 Arawn to within {{cvt|1000|km|mi}} and to determine its rotational period of 5.47 hours.<ref name="unitoday20160613">{{cite news |url=http://www.universetoday.com/129014/new-horizons-sends-back-first-science-distant-kuiper-belt-object/ |title=New Horizons Sends Back First Science On Distant Kuiper Belt Object |work=Universe Today |first=Evan |last=Gough |date=June 13, 2016 |access-date=November 5, 2016}}</ref><ref name="jhuapl20160518">{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20160518-2 |title=New Horizons Collects First Science on a Post-Pluto Object |publisher=[[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] |date=May 18, 2016 |access-date=November 5, 2016}}</ref>

In July 2016, the LORRI camera captured some distant images of [[Astronomy:50000 Quaoar|Quaoar]] from {{convert|2.1|e9km|e9mi+AU|abbr=unit|disp=x| away (|)}}; the oblique view will complement Earth-based observations to study the object's light-scattering properties.<ref name="nasa20160831">{{cite web |url=http://www.nasa.gov/image-feature/new-horizons-spies-a-kuiper-belt-companion |title=New Horizons Spies a Kuiper Belt Companion |publisher=[[Organization:NASA|NASA]] |first=Tricia |last=Talbert |date=August 31, 2016 |access-date=September 12, 2016}}</ref>

On December 5, 2017, when ''New Horizons'' was 40.9&nbsp;AU from Earth, a calibration image of the [[Astronomy:NGC 3532|Wishing Well cluster]] marked the most distant image ever taken by a spacecraft (breaking the 27-year record set by ''[[Astronomy:Voyager 1|Voyager 1]]''{{'}}s famous ''[[Astronomy:Pale Blue Dot|Pale Blue Dot]]''). Two hours later, ''New Horizons'' surpassed its own record, imaging the Kuiper belt objects {{mp|2012 HZ|84}} and {{mp|2012 HE|85}} from a distance of 0.50 and 0.34&nbsp;AU, respectively. These were the closest images taken of a Kuiper belt object besides Pluto and Arrokoth {{as of|2018|02|lc=y}}.<ref name="nasa20180208">{{cite web |url=https://www.nasa.gov/feature/new-horizons-captures-record-breaking-images-in-the-kuiper-belt |title=New Horizons Captures Record-Breaking Images in the Kuiper Belt |publisher=NASA |editor-first=Bill |editor-last=Keeter |date=February 8, 2018 |access-date=February 9, 2018}}</ref><ref>{{cite web |url=https://ssd.jpl.nasa.gov/horizons.cgi |title=HORIZONS Web-Interface, Ephemeris Type: VECTORS, Target Body: Asteroid (2012 HE85), Coordinate Origin: New Horizons Spacecraft [500@-98], Time Span: Start=2017-12-05, Stop=2017-12-06, Intervals=1 |work=[[Astronomy:JPL Horizons On-Line Ephemeris System|JPL Horizons On-Line Ephemeris System]] |access-date=February 8, 2018 |archive-date=August 13, 2011 |archive-url=https://web.archive.org/web/20110813225539/http://ssd.jpl.nasa.gov/horizons.cgi |url-status=live }}</ref>

The dwarf planet [[Astronomy:Haumea|Haumea]] was observed from afar by the ''New Horizons'' spacecraft in October 2007, January 2017, and May 2020, from distances of 49&nbsp;AU, 59&nbsp;AU, and 63&nbsp;AU, respectively. ''New Horizons'' has observed the dwarf planets Eris (2020), Haumea (2007, 2017, 2020), Makemake (2007, 2017), and Quaoar (2016, 2017, 2019), as well as the large KBOs [[Astronomy:28978 Ixion|Ixion]] (2016), {{mpl-|307261|2002 MS|4}} (2016, 2017, 2019), and {{mpl-|556416|2014 OE|394}} (2017, 2018). It also observed Neptune's largest moon [[Astronomy:Triton (moon)|Triton]] (which shares similarities with Pluto and Eris) in 2019.<ref name="Verbiscer2022">{{cite journal
  |display-authors = etal
  |first1 = Anne J. |last1 = Verbiscer
  |first2 = Paul |last2 = Helfenstein
  |first3 = Simon B. |last3 = Porter
  |first4 = Susan D. |last4 = Benecchi
  |first5 = J. J. |last5 = Kavelaars
  |first6 = Tod R. |last6 = Lauer
  |title      = The Diverse Shapes of Dwarf Planet and Large KBO Phase Curves Observed from New Horizons
  |journal    = The Planetary Science Journal
  |date       = April 2022
  |volume     = 3
  |issue      = 4
  |id         = 95
  |pages      = 31
  |doi-access = free
  |doi        = 10.3847/PSJ/ac63a6
  |bibcode    = 2022PSJ.....3...95V}}</ref>

{{Multiple image |align=center |total_width=800
 |header=Extended mission imaging targets
 |image1=PIA205891994 JR1newhorizons.gif |caption1=[[Astronomy:15810 Arawn|15810 Arawn]] in April 2016
 |image2=Quaoar_animation_dark_crsub_circle.gif |caption2=[[Astronomy:50000 Quaoar|50000 Quaoar]] in July 2016 at a distance of about 14&nbsp;AU<ref name="nasa20160831" />
 |image3=Wishing Well cluster New Horizons.png |caption3=Calibration image of the [[Astronomy:NGC 3532|Wishing Well cluster]] from December 2017
 |image4=2012 HZ84 by New Horizons.jpg |caption4=False-color image of {{mpl|2012 HZ|84}} from December 2017
 |image5=2012 HE85 by New Horizons.jpg |caption5=False-color image of {{mpl|2012 HE|85}} from December 2017
 |footer= <!-- Conflict between Wikimedia Commons "Category:Photos of Kuiper belt objects by New Horizons" and Wikidata in § Observations of other KBOs; preview-only error message. This hidden text dated 17 December 2020 UTC. -->
 
}}

By December 2023, ''New Horizons'' had discovered a total of about 100 KBOs, and flown close enough to about 20 of them to capture characteristics such as shape, rotational period, possible moons, and surface composition. In addition, since 2021, Canadian researchers had been able to use [[Machine learning|machine learning]] software to speed up identification processes of potential KBO targets for a third flyby, cutting weeks-long efforts to hours-long.<ref name="Verbiscer2022"/><ref name="Hope 2023">{{cite web | last=Hope | first=Diane | title=Deep into the Kuiper Belt, New Horizons is still doing science | website=Ars Technica | date=December 12, 2023 | url=https://arstechnica.com/science/2023/12/squeezing-science-out-of-new-horizons-as-it-heads-out-of-the-solar-system/ | access-date=December 14, 2023}}</ref>

== Encounter with Arrokoth ==
[[File:New Horizons flyby of 2014 MU69 (Eyes on the Solar System).ogg|thumb|Animation of New Horizons' flyby of Arrokoth in [[Software:NASA's Eyes|Eyes on the Solar System]].]]
[[File:Animation of New Horizons trajectory.gif|thumb|right|Animation of ''New Horizons''{{'s}} trajectory from January 19, 2006, to  December 30, 2030<br /> {{legend2|magenta| ''New Horizons'' }}{{·}}{{legend2|lime|486958 Arrokoth}}{{·}}{{legend2|Royalblue|[[Astronomy:Earth|Earth]]}}{{·}}{{legend2|Gold|132524 APL}}{{·}}{{legend2|OrangeRed|Jupiter }}{{·}}{{legend2|Cyan|Pluto }}]]
[[File:UltimaThule CA06 color vertical.png|thumb|''New Horizons'' image of Arrokoth]]{{See also|486958 Arrokoth #Exploration}}

=== Objectives ===
Science objectives of the flyby included characterizing the geology and morphology of [[Astronomy:486958 Arrokoth|Arrokoth]]<ref name="NYT-20181231">{{cite news |last=Chang |first=Kenneth |title=NASA's New Horizons Will Visit Ultima Thule on New Year's Day – The probe that visited Pluto will study a mysterious icy world just after midnight. Arrokoth will be the most distant object ever visited by a spacecraft. |url=https://www.nytimes.com/2018/12/31/science/ultima-thule-pictures-new-horizons.html |date=December 31, 2018 |work={{wipe|The New York Times}} |access-date=December 31, 2018 |archive-date=February 29, 2020 |archive-url=https://web.archive.org/web/20200229203949/https://www.nytimes.com/2018/12/31/science/ultima-thule-pictures-new-horizons.html |url-status=live }}</ref><ref name="NYT-20181230">{{cite news |last=Chang |first=Kenneth |title=A Journey Into the Solar System's Outer Reaches, Seeking New Worlds to Explore |url=https://www.nytimes.com/2018/12/30/science/nasa-new-horizons-kuiper-belt.html |date=December 30, 2018 |work={{wipe|The New York Times}} |access-date=December 30, 2018 |archive-date=April 3, 2020 |archive-url=https://web.archive.org/web/20200403135023/https://www.nytimes.com/2018/12/30/science/nasa-new-horizons-kuiper-belt.html |url-status=live }}</ref> and mapping the surface composition (by searching for ammonia, carbon monoxide, methane, and water ice). Searches will be conducted for orbiting moonlets, a coma, rings and the surrounding environment.<ref name="2017 AGU"/> Additional objectives include:<ref name="skytel20151001">{{cite news |url=http://www.skyandtelescope.com/astronomy-news/new-horizons-a-billion-miles-to-2014-mu69-10012015/
 |title=New Horizons: A Billion Miles to {{mp|486958|2014 MU|69}}
 |work=Sky & Telescope |last=Stern |first=Alan
 |date=October 1, 2015 |access-date=October 3, 2015}}</ref>

*Mapping the surface geology to learn how it formed and evolved
*Measuring the surface temperature
*Mapping the 3-D surface topography and surface composition to learn how it is similar to and different from comets such as 67P/Churyumov–Gerasimenko and dwarf planets such as Pluto
*Searching for any signs of activity, such as a cloud-like coma
*Searching for and studying any satellites or rings
*Measuring or constraining the mass

=== Targeting maneuvers ===
Arrokoth is the first object to be targeted for a flyby that was discovered after the spacecraft was launched.<ref name="Lakdawalla20150901">{{cite news |url=http://www.planetary.org/blogs/emily-lakdawalla/2015/09011608-new-horizons-extended-mission-pt1.html |title=New Horizons extended mission target selected |publisher=[[Organization:The Planetary Society|The Planetary Society]] |last=Lakdawalla |first=Emily |date=September 1, 2015 |access-date=September 22, 2015 |archive-date=October 18, 2015 |archive-url=https://web.archive.org/web/20151018200350/http://www.planetary.org/blogs/emily-lakdawalla/2015/09011608-new-horizons-extended-mission-pt1.html |url-status=live }}</ref> ''New Horizons'' was planned to come within {{convert|3500|km|mi|abbr=on}} of Arrokoth, three times closer than the spacecraft's earlier encounter with Pluto. Images with a resolution of up to {{convert|30|m|ft|abbr=on}} per pixel were expected.<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20170906 |title=New Horizons Files Flight Plan for 2019 Flyby |publisher=[[Organization:Applied Physics Laboratory|Johns Hopkins University Applied Physics Laboratory]] |date=September 6, 2017 |access-date=December 28, 2017 |archive-date=August 31, 2019 |archive-url=https://web.archive.org/web/20190831062326/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20170906 |url-status=live }}</ref>

The new mission began on October 22, 2015, when ''New Horizons'' carried out the first in a series of four initial targeting maneuvers designed to send it towards Arrokoth. The maneuver, which started at approximately 19:50&nbsp;UTC and used two of the spacecraft's small hydrazine-fueled thrusters, lasted approximately 16 minutes and changed the spacecraft's trajectory by about {{convert|10|m/s|ft/s|sp=us}}. The remaining three targeting maneuvers took place on October 25, October 28, and November 4, 2015.<ref name="spdaily20151106">{{cite news |url=http://www.spacedaily.com/reports/New_Horizons_Completes_Targeting_Maneuvers_999.html |title=New Horizons Completes Targeting Maneuvers |work=Space Daily |date=November 6, 2015 |access-date=December 19, 2015}}</ref><ref name="jhuapl20151029">{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20151029 |title=On Track: New Horizons Carries Out Third KBO Targeting Maneuver |publisher=Johns Hopkins University Applied Physics Laboratory |date=October 29, 2015 |access-date=December 19, 2015 |archive-date=January 5, 2016 |archive-url=https://web.archive.org/web/20160105082024/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20151029 |url-status=live }}</ref>

=== Approach phase ===
The craft was brought out of its hibernation at approximately 00:33&nbsp;[[UTC]] [[Physics:Spacecraft Event Time|{{abbr|SCET|Spacecraft Event Time}}]] on June 5, 2018 (06:12&nbsp;UTC [[Physics:Spacecraft Event Time|ERT]], Earth-Received Time),{{refn|group="lower-alpha"|name="note"|Confirmation that ''New Horizons'' exited hibernation was received by ground stations at 06:12&nbsp;UTC. [[Physics:Spacecraft Event Time|Spacecraft Event Time]] is calculated by subtracting the one-way light-travel time (5 hours, 38 minutes, 38 seconds) from Earth-received time.<ref name="position20180606">{{cite web |url=http://pluto.jhuapl.edu/Mission/Where-is-New-Horizons/index.php |title=New Horizons: Current Position |publisher=[[Organization:Johns Hopkins University|Johns Hopkins University]] [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] |date=June 6, 2018 |archive-url=https://web.archive.org/web/20180607001308/http://pluto.jhuapl.edu/Mission/Where-is-New-Horizons/index.php |archive-date=June 7, 2018}}</ref>}} in order to prepare for the approach phase.<ref name="verge20180605">{{cite news |url=https://www.theverge.com/2018/6/5/17429698/nasa-new-horizons-ultima-thule-2014-mu69-pluto-flyby |title=NASA's New Horizons probe woke up today to prep for its next deep space flyby |work=[[The Verge]] |first=Loren |last=Grush |date=June 5, 2018 |access-date=June 6, 2018}}</ref><ref name="jhuapl20180605">{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20180605 |title=New Horizons Wakes for Historic Kuiper Belt Flyby |publisher=[[Organization:Johns Hopkins University|Johns Hopkins University]] [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] |date=June 5, 2018 |access-date=June 6, 2018}}</ref> After verifying its health status, the spacecraft transitioned from a [[Engineering:Spin-stabilisation|spin-stabilized]] mode to a three-axis-stabilized mode on August 13, 2018. The official approach phase began on August 16, 2018, and continued through December 24, 2018.<ref name="Planetary">{{cite web |url=http://www.planetary.org/blogs/emily-lakdawalla/2018/0124-new-horizons-prepares-for-2014mu69.html |title=New Horizons prepares for encounter with 2014 MU69 |publisher=[[Organization:The Planetary Society|The Planetary Society]] |last1=Lakdawalla |first1=Emily |date=January 24, 2018 |access-date=January 26, 2018 |archive-date=February 20, 2018 |archive-url=https://web.archive.org/web/20180220213605/http://www.planetary.org/blogs/emily-lakdawalla/2018/0124-new-horizons-prepares-for-2014mu69.html |url-status=live }}</ref>

''New Horizons'' made its first detection of Arrokoth on August 16, 2018, from a distance of {{convert|107|e6mi|e6km|abbr=unit}}. At that time, Arrokoth was visible at magnitude 20 against a crowded stellar background in the direction of the constellation [[Astronomy:Sagittarius (constellation)|Sagittarius]].<ref name="First detection">{{cite web|url=https://www.nasa.gov/feature/ultima-in-view-nasa-s-new-horizons-makes-first-detection-of-kuiper-belt-flyby-target|title=Ultima in View: NASA's New Horizons Makes First Detection of Kuiper Belt Flyby Target|date=August 28, 2018|access-date=August 28, 2018|publisher=NASA|archive-date=January 24, 2020|archive-url=https://web.archive.org/web/20200124212405/https://www.nasa.gov/feature/ultima-in-view-nasa-s-new-horizons-makes-first-detection-of-kuiper-belt-flyby-target/|url-status=live}}</ref><ref name="JPLHorizonsX">{{cite web|url=https://ssd.jpl.nasa.gov/horizons.cgi|title=JPL Horizons|access-date=August 28, 2018|publisher=JPL|archive-date=August 13, 2011|archive-url=https://web.archive.org/web/20110813225539/http://ssd.jpl.nasa.gov/horizons.cgi|url-status=live}}</ref>

=== Flyby ===
The Core phase began a week before the encounter and continued for two days after the encounter. The spacecraft flew by the object at a speed of {{cvt|51500|kph|mph km/s|abbr=on}} and within {{cvt|3500|km|abbr=on}}.<ref>[https://www.skyandtelescope.com/astronomy-news/new-horizons-approaching-ultima-thule/ New Horizons: Ultima Thule is Dead Ahead]. Allan Stern, ''Sky and Telescope.'' December 26, 2018.</ref> The majority of the science data was collected within 48 hours of the closest approach in a phase called the Inner Core.<ref name="Planetary"/> Closest approach occurred January 1, 2019, at 05:33&nbsp;[[UTC]]<ref name="sfnow20180106">{{cite news |url=https://spaceflightnow.com/2018/01/06/plot-thickens-as-new-horizons-moves-within-year-of-next-flyby/ |title=Plot thickens as New Horizons moves within year of next flyby |work=Spaceflight Now |first=Stephen |last=Clark |date=January 6, 2018 |access-date=January 11, 2018}}</ref> [[Physics:Spacecraft Event Time|SCET]] at which point the probe was {{val|43.4|ul=AU}} from the [[Astronomy:Sun|Sun]].<ref>{{cite web |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20151023 |title=Maneuver Moves New Horizons Spacecraft toward Next Potential Target |date=October 23, 2015 |access-date=November 5, 2015 |archive-date=October 25, 2015 |archive-url=https://web.archive.org/web/20151025193927/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20151023 |url-status=live }}</ref> At this distance, the one-way transit time for radio signals between Earth and ''New Horizons'' was six hours.<ref name="2017 AGU">{{cite journal |last1=Green |first1=Jim |title=New Horizons Explores the Kuiper Belt |journal=2017 American Geophysical Union (AGU) Fall Meeting in New Orleans |date=December 12, 2017 |pages=12–15 |url=http://pluto.jhuapl.edu/News-Center/Press-Conferences/December-12-2017.php |access-date=December 13, 2017 |archive-url=https://web.archive.org/web/20171213092759/http://pluto.jhuapl.edu/News-Center/Press-Conferences/December-12-2017.php |archive-date=December 13, 2017 |url-status=dead }}</ref> Confirmation that the craft had succeeded in filling its digital recorders occurred when data arrived on Earth ten hours later, at 15:29 UTC.<ref>{{cite web |title=New Horizons Successfully Explores Ultima Thule |url=http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20190101 |publisher=Johns Hopkins Applied Physics Laboratory |date=Jan 1, 2019 |access-date=January 4, 2019 |archive-date=January 1, 2019 |archive-url=https://web.archive.org/web/20190101164301/http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20190101 |url-status=live }}</ref>

=== Data download ===

After the encounter, preliminary, high-priority data was sent to Earth on January 1 and 2, 2019. On January 9, ''New Horizons'' returned to a spin-stabilized mode to prepare sending the remainder of its data back to Earth.<ref name="Planetary"/> This download was expected to take 20 months at a data rate of 1–2 kilobits per second.<ref>{{cite web| title=New Horizons Data Collection| url=https://pluto.jhuapl.edu/Mission/Spacecraft/Data-Collection.php| publisher=Johns Hopkins Applied Physics Center| access-date=January 1, 2019| archive-date=December 28, 2018| archive-url=https://web.archive.org/web/20181228180823/http://pluto.jhuapl.edu/Mission/Spacecraft/Data-Collection.php| url-status=dead}}</ref>
As of July 2022, approximately 10% of the data was still left to be received.<ref>{{cite web |author1=Leonard David |title=Far beyond Pluto: What's next for NASA's New Horizons probe? |url=https://www.space.com/beyond-pluto-nasa-new-horizons-next-steps |website=Space.com |access-date=2 August 2022 |language=en |date=14 July 2022}}</ref>

== Post-Arrokoth events ==

[[File:New Horizons Proxima Centauri Parallax Animation.gif|thumb|Parallax of Proxima Centauri as observed from New Horizons and Earth.<ref name=":0" />]]

In April 2020, ''New Horizons'' was used in conjunction with telescopes on Earth to take pictures of nearby stars [[Astronomy:Proxima Centauri|Proxima Centauri]] and [[Astronomy:Wolf 359|Wolf 359]]; the images from each vantage point – over 4 billion miles (6.4 billion km) apart – were compared to produce "the first demonstration of an easily observable [[Astronomy:Stellar parallax|stellar parallax]]."<ref name=":0">{{Cite web |last=Talbert |first=Tricia |date=2020-07-10 |title=New Horizons Conducts the First Interstellar Parallax Experiment |url=http://www.nasa.gov/feature/nasa-s-new-horizons-conducts-the-first-interstellar-parallax-experiment |url-status=live |archive-url=https://web.archive.org/web/20231104161749/https://www.nasa.gov/solar-system/nasas-new-horizons-conducts-the-first-interstellar-parallax-experiment/ |archive-date=2023-11-04 |access-date=2020-07-14 |website=NASA |language=en}}</ref>

Images taken by the LORRI camera while ''New Horizons'' was 42 to 45 AU from the Sun were used to measure the cosmic optical background, the visible light analog of the [[Astronomy:Cosmic microwave background|cosmic microwave background]], in seven high galactic latitude fields. At that distance ''New Horizons'' saw a sky ten times darker than the sky seen by the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] because of the absence of diffuse background sky brightness from the [[Astronomy:Zodiacal light|zodiacal light]] in the inner solar system. These measurements indicate that the total amount of light emitted by all galaxies at ultraviolet and visible wavelengths may be lower than previously thought.<ref name="laueretal"/><ref name="COBPress"/>

[[File:New Horizons Full Trajectory Sideview.svg|thumb|''New Horizons''{{'}} position<ref name="currentposition" />]]

The spacecraft reached a distance of {{convert|50|AU|e9km e9mi|abbr=unit}} on April 17, 2021, at 12:42 UTC, a feat performed only four times before, by ''[[Astronomy:Pioneer 10|Pioneer 10]]'', ''[[Astronomy:Pioneer 11|Pioneer 11]]'', ''[[Astronomy:Voyager 1|Voyager 1]]'', and ''[[Astronomy:Voyager 2|Voyager 2]]''. ''Voyager 1'' is the farthest spacecraft from the Sun, more than {{convert|152|AU|e9km e9mi|abbr=unit}} away when ''New Horizons'' reached its landmark in 2021.<ref>[http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20210415 NASA's New Horizons Reaches a Rare Space Milestone] NASA, April 15, 2021.</ref> The support team continued to use the spacecraft in 2021 to study the [[Astronomy:Heliosphere|heliospheric]] environment (plasma, dust and gas) and to study other Kuiper Belt objects.<ref>[http://www.collectspace.com/news/news-041521a-new-horizons-50-au-voyager-photo.html NASA's New Horizons reaches rare distance, looks out to Voyager] CollectSpace, April 15, 2021.</ref>

=== Plans ===
After the spacecraft passed Arrokoth, the instruments continue to have enough power to be operational until the 2030s.

Team leader Alan Stern stated there is potential for a third flyby in the 2020s at the outer edges of the Kuiper belt.<ref>{{cite news|date=December 21, 2018|title=New Horizons May Make Yet Another Flyby After Ultima Thule|website=Space.com|url=https://www.space.com/42808-nasa-new-horizons-possible-third-flyby.html|access-date=January 2, 2019}}</ref><ref>{{cite web|date=September 11, 2017|title=New Horizons planning additional extended missions|url=https://spacenews.com/new-horizons-planning-additional-extended-missions/|access-date=January 1, 2019|website=SpaceNews.com|language=en-US}}</ref> This depends on a suitable Kuiper belt object being found or confirmed close enough to the spacecraft's current trajectory. Since May 2020, the ''New Horizons'' team has been using time on the [[Astronomy:Subaru Telescope|Subaru Telescope]] to look for suitable candidates within the spacecraft's proximity. {{As of|2023|10}}, none had been found close enough to the trajectory of ''New Horizons'' for it to be able to make a close flyby with its remaining fuel. However, the mission continues to be funded as a planetary science mission, rather than as a pure heliophysics mission as NASA officials suggested in spring 2023.<ref name="jhuapl_20201104_newhorizons">{{Cite web |url=http://pluto.jhuapl.edu/News-Center/PI-Perspectives.php?page=piPerspective_11_04_2020 |title = New Horizons: The PI's Perspective: Far from Home |date=November 4, 2020 |access-date=April 28, 2023 |archive-url=https://web.archive.org/web/20230403211646/http://pluto.jhuapl.edu/News-Center/PI-Perspectives.php?page=piPerspective_11_04_2020 |archive-date=April 3, 2023 |url-status=dead}}</ref><ref name="Kornfeld 2023">{{cite web | last=Kornfeld | first=Laurel | title=New Horizons to remain a planetary mission through decade's end | website=SpaceFlight Insider | date=October 11, 2023 | url=https://www.spaceflightinsider.com/missions/solar-system/new-horizons-to-remain-a-planetary-mission-through-decades-end/ | access-date=December 14, 2023}}</ref>

''New Horizons'' may also take a picture of Earth from its distance in the Kuiper belt, but only after completing all planned KBO flybys and imaging Uranus and Neptune.<ref>{{cite web|last=Stern|first=Alan|title=Hi, I am Alan Stern, head of NASA's New Horizons spacecraft on its way to explore Ultima Thule, a Kuiper Belt object one billion miles beyond Pluto! AMA|date=December 11, 2018|url=https://www.reddit.com/r/space/comments/a581g4/hi_i_am_alan_stern_head_of_nasas_new_horizons/ebkny1l}}</ref><ref name="Kornfeld 2023"/> This is because pointing a camera towards Earth could cause the camera to be damaged by sunlight,<ref>{{Cite news|last=Koren|first=Marina|date=February 13, 2018|title=Astronomers Are Already Planning for the Next 'Pale Blue Dot'|work=The Atlantic|url=https://www.theatlantic.com/science/archive/2018/02/new-horizons-pale-blue-dot-nasa/553160/|access-date=January 1, 2019}}</ref> as none of ''New Horizons''' cameras have an active shutter mechanism.<ref>{{Cite web|title=About LORRI Images|url=http://pluto.jhuapl.edu/soc/lorri_about.html|access-date=2019-12-14|website=pluto.jhuapl.edu}}</ref><ref>{{cite web|date=September 2007|title=New Horizons SOC to Instrument Pipeline ICD|url=https://pds-rings.seti.org/newhorizons/SOC_INST_ICD.PDF|access-date=November 3, 2020|publisher=Southwest Research Institute}}</ref>

== Speed ==
[[File:New Horizons Speed and distance from Sun.svg|thumb|right|Speed and distance from the Sun]]
''New Horizons'' has been called "the fastest spacecraft ever launched"<ref name="APL-20070116">{{cite web |url=http://pluto.jhuapl.edu/News-Center/Resources/Press-Kits/011607_JupiterPressKit.pdf |title=New Horizons, The First Mission to Pluto and the Kuiper Belt: Exploring Frontier Worlds |publisher=[[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] |type=Press Kit |date=January 16, 2007}}</ref> because it left Earth at {{convert|16.26|km/s|km/h mph|0|sp=us}}.<ref name="sciam20130225">{{cite web |url=https://blogs.scientificamerican.com/life-unbounded/the-fastest-spacecraft-ever/ |title=The Fastest Spacecraft Ever? |work=Scientific American |first=Caleb A. |last=Scharf |date=February 25, 2013 |access-date=July 12, 2017}}</ref><ref name="ionine20150609">{{cite news |url=http://io9.gizmodo.com/heres-why-the-new-horizons-spacecraft-wont-be-stopping-1710069685 |title=Here's Why The New Horizons Spacecraft Won't Be Stopping At Pluto |work=io9 |first=George |last=Dvorsky |date=June 9, 2015 |access-date=July 12, 2017}}</ref> It is also the first spacecraft launched directly into a solar escape trajectory, which requires an approximate speed while near Earth of {{cvt|16.5|km/s|km/h mph}},<ref group="lower-alpha">To escape the Sun, the spacecraft needs a speed relative to the Sun of the square root of 2 times the speed of the Earth, which is 29.78&nbsp;km/s. (In other words, <math>\sqrt2\cdot 29.78 \text{ km/s}\approx 42.11\text{ km/s}</math>.) Relative to the Earth, this is just 12.3&nbsp;km/s. But the kinetic energy when near the surface of the Earth must include the energy to exit the gravity well of the Earth, which requires a speed of about 11 km/s. The total speed needed is the square root of the sum of the squares of these two speeds.{{citation needed|date=January 2018}}</ref> plus additional [[Astronomy:Delta-v|delta-''v'']] to cover air and [[Astronomy:Gravity drag|gravity drag]], all to be provided by the launch vehicle. {{As of|2024|01|17|df=US}}, the spacecraft is {{convert|57.97|AU|e9km e9mi|abbr=unit}} from the Sun traveling at {{Cvt|13.71|km/s|km/h mph}}.<ref>{{Cite web |title=Current Position — New Horizons |url=https://pluto.jhuapl.edu/Mission/Where-is-New-Horizons.php|access-date=2023-07-13 |website=pluto.jhuapl.edu}}</ref> <!-- DO NOT UPDATE THIS MORE THAN ONCE A MONTH -->

However, it is not the fastest spacecraft to leave the Solar System. {{as of|2023|07}}, this record is held by ''Voyager 1'', traveling at {{cvt|16.985|km/s|km/h mph|0}} relative to the Sun.<ref name="heavens-escaping" /> ''Voyager 1'' attained greater hyperbolic excess velocity than ''New Horizons'' due to [[Astronomy:Gravity assist|gravity assist]]s by Jupiter and Saturn.  When ''New Horizons'' reaches the distance of {{convert|100|AU|e9km e9mi|abbr=unit}}, it will be traveling at about {{cvt|13|km/s|km/h mph}}, around {{cvt|4|km/s|km/h mph}} slower than ''Voyager 1'' at that distance.<ref name="jhuapl2006">{{cite web|url=http://spaceref.com/news/viewpr.html?pid=20620|title=New Horizons Salutes Voyager|date=August 17, 2006|publisher=Johns Hopkins APL|archive-url=https://web.archive.org/web/20141113224847/http://pluto.jhuapl.edu/news_center/news/081706.php|archive-date=November 13, 2014|url-status=dead|access-date=November 3, 2009}}</ref> The [[Astronomy:Parker Solar Probe|Parker Solar Probe]] can also be measured as the fastest object, because of its [[Astronomy:Orbital speed|orbital speed]] relative to the Sun at [[Astronomy:Apsis|perihelion]]: {{cvt|95.3|km/s|km/h mph}}.{{refn|group="lower-alpha"|name="parker-note"}} Because it remains in solar orbit, its [[Astronomy:Specific orbital energy|specific orbital energy]] relative to the Sun is lower than ''New Horizons'' and other artificial objects escaping the Solar System.


== Gallery ==

=== Images of the launch ===
{{Multiple image |align=center |total_width=800
 |image1=Atlas 551 rocket prepared for launch.jpg |caption1=The Atlas V 551 rocket, used to launch ''New Horizons'', being processed a month before launch.
 |image2=Atlas V 551 at Launch Pad 41.jpg |caption2=View of Cape Canaveral Launch Complex 41, with the Atlas V carrying ''New Horizons'' on the pad.
 |image3=D6-17018ML.jpg |caption3=Distant view of Cape Canaveral during the launch of ''New Horizons'' on January 19, 2006.
 |image4=NASA TV - New Horizons Pluto Launch (January 19, 2006).ogg |caption4=NASA TV footage of ''New Horizons''{{'}} launch from Cape Canaveral. (4:00)
}}

=== Videos ===
{{Multiple image |align=center |total_width=800 |caption_align=center
 |image1=Pluto-FlyoverAnimation-20150918.webm |caption1=(00:30; [[:File:Pluto-FlyoverAnimation-20150918.webm|released September 18, 2015]])
 |image2=15-02652-PlutoFilm-50sec-20150714.webm |caption2=(00:50; [[:File:15-02652-PlutoFilm-50sec-20150714.webm|released December 5, 2015]])
}}
{{Clear}}

== See also ==
{{div col|colwidth=30em}}
* 2006 in spaceflight
* [[Astronomy:Exploration of Pluto|Exploration of Pluto]]
* List of artificial objects leaving the Solar System
* [[Astronomy:List of missions to the outer planets|List of missions to the outer planets]]
* [[Astronomy:List of New Horizons topics|List of ''New Horizons'' topics]]
* [[Astronomy:Mariner Mark II|Mariner Mark II]], a planned family of NASA spacecraft including a Pluto mission
* ''[[Astronomy:New Horizons 2|New Horizons 2]]'', a proposed trans-Neptunian object flyby mission
* ''[[Astronomy:Pioneer 10|Pioneer 10]]''
* ''[[Astronomy:Pioneer 11|Pioneer 11]]''
* ''[[Astronomy:Pluto Kuiper Express|Pluto Kuiper Express]]'', a cancelled NASA Pluto flyby mission
* ''[[Engineering:TAU (spacecraft)|TAU]]'', a proposed mission to fly by Pluto
* [[Astronomy:Timeline of Solar System exploration|Timeline of Solar System exploration]]
* ''[[Astronomy:Voyager 1|Voyager 1]]''
* ''[[Astronomy:Voyager 2|Voyager 2]]''
{{div col end}}

== Notes ==
{{Reflist|group=lower-alpha}}

== References ==
{{Reflist|colwidth=30em|refs=
<ref name="Moore-2010">{{cite book |url=https://books.google.com/books?id=7u7k3qBd-boC&pg=PA35 |title=The Sky at Night |publisher=Springer |last=Moore |first=Patrick |page=35 |date=2010 |isbn=978-1-4419-6408-3}}<!-- not a quote in the article as there is a word-order misprint in the book which would distract if visibly corrected --></ref>
<ref name="laueretal">{{cite web |last1=Lauer |first1=Tod R. |last2=Postman |first2=Marc |last3=Weaver |first3=Harold A.. |last4=Spencer |first4=John R. |last5=Stern |first5=S. Alan |last6=Buie |first6=Marc W. |last7=Durda |first7=Daniel D. |last8=Lisse |first8=Carey M. |last9=Poppe |first9=A.R. |last10=Binzel |first10=Richard P. |last11=Britt |first11=Daniel T. |last12=Buratti |first12=Bonnie J. |last13=Cheng |first13=Andrew F. |last14=Grundy |first14=W.M. |last15=Horanyi |first15=Mihaly |last16=Kavelaars |first16=J.J. |last17=Linscott |first17=Ivan R. |last18=McKinnon |first18=William B. |last19=Moore |first19=Jeffrey M. |last20=Nunez |first20=J.I. |last21=Olkin |first21=Catherine B. |last22=Parker |first22=Joel W. |last23=Porter |first23=Simon B. |last24=Reuter |first24=Dennis C. |last25=Robbins |first25=Stuart J. |last26=Schenk |first26=Paul |last27=Showalter |first27=Mark R. |last28=Singer |first28=Kelsi N. |last29=Verbiscer |first29=Anne. J. |last30=Young |first30=Leslie A. |title=New Horizons Observations of the Cosmic Optical Background |url=https://imgsrc.hubblesite.org/hvi/uploads/science_paper/file_attachment/622/2011.03052.pdf |website=Hubblesite |publisher=NASA |access-date=18 January 2021 |archive-date=January 21, 2021 |archive-url=https://web.archive.org/web/20210121164355/https://imgsrc.hubblesite.org/hvi/uploads/science_paper/file_attachment/622/2011.03052.pdf |url-status=dead }}</ref>
<ref name="COBPress">{{cite web |title=New Horizons Spacecraft Answers Question: How Dark Is Space? |url=https://hubblesite.org/contents/news-releases/2021/news-2021-01 |website=Hubblesite |publisher=NASA |access-date=18 January 2021}}</ref>
}}

== Further reading ==
* {{Cite journal |last1=Guo |first1=Yanping |last2=Farquhar |first2=Robert W. |url=http://www.boulder.swri.edu/~tcase/Guo_Acta56_2005.pdf |title=New Horizons Pluto–Kuiper Belt mission: design and simulation of the Pluto–Charon encounter |journal=Acta Astronautica |volume=56 |issue=3 |pages=421–429 |date=February 2005 |doi=10.1016/j.actaastro.2004.05.076 |bibcode=2005AcAau..56..421G}}
* {{cite journal |first=Michael J. |last=Neufeld |url=https://airandspace.si.edu/blogmedia/neufeld-new-horizons-2015.pdf |title=First Mission to Pluto: Policy, Politics, Science, and Technology in the Origins of New Horizons, 1989–2003 |journal=Historical Studies in the Natural Sciences |volume=44 |issue=3 |pages=234–276 |date=November 2012 |doi=10.1525/hsns.2014.44.3.234 |archive-url=https://web.archive.org/web/20150907015621/https://airandspace.si.edu/blogmedia/neufeld-new-horizons-2015.pdf |archive-date=September 7, 2015}}
* {{cite book |title=New Horizons: Reconnaissance of the Pluto-Charon System and the Kuiper Belt |publisher=Springer |first=Christopher T. |last=Russell |date=2009 |isbn=978-0-387-89517-8}}
* {{cite book |title=Chasing New Horizons: Inside the Epic First Mission to Pluto |publisher=Picador |first1=Alan |last1=Stern |first2=David |last2=Grinspoon |date=2018 |isbn=978-125009896-2}}

== External links ==
* [https://science.nasa.gov/mission/new-horizons/ ''New Horizons'' website] by NASA
* [http://pluto.jhuapl.edu/ ''New Horizons'' website] by the [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]]
* [https://web.archive.org/web/20160205053300/http://solarsystem.nasa.gov/missions/newhorizons ''New Horizons'' profile] by NASA's Planetary Science Division
* [https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2006-001A ''New Horizons'' profile] by the [[Astronomy:National Space Science Data Center|National Space Science Data Center]]
* [http://pluto.jhuapl.edu/News-Center/Where-to-Watch.php ''New Horizons'' Flyby] of ''Ultima Thule'' – Best Places to Follow Future News.
* [https://www.youtube.com/watch?v=j3Jm5POCAj8 ''New Horizons'' Flyby] – Musical Tribute by astrophysicist Brian May (who consulted on the project<ref>"[https://www.npr.org/2019/01/02/681535239/queen-guitarist-brian-may-contributes-to-nasa-s-new-horizons-probe NASA Gets Some Help From Guitarist Brian May On Its New Horizons Probe]", NPR, aired January 2, 2019.</ref>) and the band Queen.
* [https://pdssbn.astro.umd.edu/data_sb/missions/newhorizons/index.shtml ''New Horizons'' Mission Archive] at the NASA Planetary Data System, Small Bodies Node
* [https://pdssbn.astro.umd.edu/data_sb/missions/nh-kem/index.shtml ''New Horizons: Kuiper Belt Extended Mission (KEM)'' Mission Archive] at the NASA Planetary Data System, Small Bodies Node

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[[Category:New Horizons| ]]
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