View source for Astronomy:Double Asteroid Redirection Test

{{Short description|2021 NASA planetary defense mission}}
{{Infobox spaceflight
| name               = Double Asteroid Redirection Test
| names_list         = DART
| image              = Dart-poster3.jpg
| image_caption      = Diagram of the DART spacecraft striking [[Astronomy:Dimorphos|Dimorphos]]
| image_size         = 300px
| mission_type       = [[Astronomy:Planetary Defense Coordination Office|Planetary defense mission]]
| operator           = [[Organization:NASA|NASA]] {{\}} [[Organization:Applied Physics Laboratory|APL]]
| COSPAR_ID          = 2021-110A
| SATCAT             = 49497
| website            = {{Plainlist|
* {{url|dart.jhuapl.edu/Mission}}
}}
| mission_duration   = {{Plainlist|
{{time interval|24 November 2021 06:21:02|26 September 2022 01:14|show=md}}
}}
| spacecraft         = {{Plainlist|
* '''DART''' impactor
* '''[[Astronomy:LICIACube|LICIACube]]''' CubeSat
}}
| spacecraft_type    = 
| spacecraft_bus     = 
| manufacturer       = [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]]<br />of [[Organization:Johns Hopkins University|Johns Hopkins University]]
| launch_mass        = {{Plainlist|
* '''DART''': {{cvt|610|kg}}<ref name="DART">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2021-110A|title=DART|publisher=[[Engineering:NASA Space Science Data Coordinated Archive|NASA Space Science Data Coordinated Archive]] |access-date=February 9, 2023}}</ref>
* '''LICIACube''': {{cvt|14|kg}}
}}
| dimensions         = {{Plainlist|
* '''DART''': {{cvt|1.8|xx|1.9|xx|2.6|m}}
* '''ROSA''': {{cvt|8.5|xx|2.4|m}} (each)
}}
| power              = 6.6 kW
| launch_date        = 24 November 2021, 06:21:02 [[Physics:Coordinated Universal Time|UTC]]<ref name="DART"></ref>
| launch_rocket      = [[Engineering:Falcon 9 Block 5|Falcon 9 Block 5]], [[Engineering:List of Falcon 9 first-stage boosters|B1063.3]]
| launch_site        = Vandenberg, SLC-4E
| launch_contractor  = [[Company:SpaceX|SpaceX]]
{{Infobox spaceflight/IP
   | type            = impactor
   | object          = [[Astronomy:Dimorphos|Dimorphos]]
   | arrival_date    = 26 September 2022, 23:14 UTC<ref name="PressKit" /><ref name="spacecom-impact-time" />
}}
{{Infobox spaceflight/IP
   | type           = flyby 
   | object         = [[Astronomy:65803 Didymos|Didymos]] system
   |component       = [[Astronomy:LICIACube|LICIACube]] (deployed from DART)
   | arrival_date   = 26 September 2022, ~23:17 UTC
   | distance       = {{cvt|56.7|km}}
  }}
| instruments        = Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO)
| insignia           = 
| insignia_caption   = 
| insignia_size      = 
| programme          = '''[[Astronomy:Planetary Missions Program Office|Solar System Exploration program]]'''
| previous_mission   = 
| next_mission       = ''[[Astronomy:Europa Clipper|Europa Clipper]]''
}}

'''Double Asteroid Redirection Test''' ('''DART''') was<!-- while the LICIACube spacecraft remains active, the primary DART spacecraft and mission have been terminated --> a [[Organization:NASA|NASA]] [[Engineering:Spaceflight|space mission]] aimed at testing a method of [[Astronomy:Asteroid impact avoidance|planetary defense]] against [[Astronomy:Near-Earth object|near-Earth object]]s (NEOs).<ref name="NYT-20220907kch">{{Cite news |last=Chang |first=Kenneth |date=27 September 2022 |title=What NASA's Crash into an Asteroid Looks Like – Astronomers on Earth – and a shoebox-size Italian spacecraft called LICIACube – captured the DART mission's successful strike on Dimorphos. |work={{wipe|The New York Times}} |url=https://www.nytimes.com/2022/09/27/science/nasa-dart-asteroid-photos.html |access-date=28 September 2022}}</ref><ref name="NYT-20220925">{{Cite news |last=Chang |first=Kenneth |date=25 September 2022 |title=NASA Is About to Crash into an Asteroid. Here's How to Watch – The DART mission has been flying to its target since launching last year. On Monday night, it will connect. |work={{wipe|The New York Times}} |url=https://www.nytimes.com/2022/09/25/science/nasa-dart-asteroid.html |access-date=26 September 2022}}</ref> It was designed to assess how much a spacecraft impact deflects an asteroid through its transfer of [[Physics:Momentum|momentum]] when hitting the asteroid head-on.<ref>{{Cite web |date=27 September 2022 |title=NASA's DART Mission Hits Asteroid in First-Ever Planetary Defense Test |url=https://www.nasa.gov/press-release/nasa-s-dart-mission-hits-asteroid-in-first-ever-planetary-defense-test |publisher=NASA}}</ref> The selected target asteroid, [[Astronomy:Dimorphos|Dimorphos]], is a [[Astronomy:Minor-planet moon|minor-planet moon]] of the asteroid [[Astronomy:65803 Didymos|Didymos]]; neither asteroid poses an impact threat to Earth, but their joint characteristics made them an ideal benchmarking target. Launched on 24 November 2021, the DART spacecraft successfully collided with Dimorphos on 26 September 2022 at 23:14 UTC about {{convert|11|e6km|sp=us|e6mi|abbr=off}} from Earth. The collision shortened Dimorphos' orbit by 32 minutes, greatly in excess of the pre-defined success threshold of 73 seconds.<ref name="NYT-20220926kc">{{Cite news |last=Chang |first=Kenneth |date=26 September 2022 |title=NASA Smashes into an Asteroid, Completing a Mission to Save a Future Day |work={{wipe|The New York Times}} |url=https://www.nytimes.com/2022/09/26/science/dart-nasa-asteroid-dimorphos-contact.html |access-date=27 September 2022}}</ref><ref>{{Cite web |last=Bardan |first=Roxana |date=2022-10-11 |title=NASA Confirms DART Mission Impact Changed Asteroid's Motion in Space |url=http://www.nasa.gov/press-release/nasa-confirms-dart-mission-impact-changed-asteroid-s-motion-in-space |access-date=2022-10-11 |website=NASA}}</ref><ref>{{Cite web |last=Strickland |first=Ashley |date=2022-10-11 |title=The DART mission successfully changed the motion of an asteroid |url=https://www.cnn.com/2022/10/11/world/nasa-dart-success-update-scn/index.html |access-date=2022-10-11 |website=CNN |language=en}}</ref> DART's success in deflecting Dimorphos was due to the momentum transfer associated with the recoil of the ejected debris, which was substantially larger than that caused by the impact itself.<ref name="Nature March2023" /> 

DART was a joint project between NASA and the [[Organization:Johns Hopkins University|Johns Hopkins]] [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]]. The project was funded through NASA's [[Astronomy:Planetary Defense Coordination Office|Planetary Defense Coordination Office]], managed by NASA's Planetary Missions Program Office at the [[Organization:Marshall Space Flight Center|Marshall Space Flight Center]], and several NASA laboratories and offices provided [[Technical support|technical support]]. The [[Organization:Italian Space Agency|Italian Space Agency]] contributed [[Astronomy:LICIACube|LICIACube]], a [[Engineering:CubeSat|CubeSat]] which photographed the impact event, and other international partners, such as the [[Organization:European Space Agency|European Space Agency]] (ESA), and Japan Aerospace Exploration Agency (JAXA), are contributing to related or subsequent projects.<ref>{{Cite web |last=Keeter |first=Bill |date=7 September 2022 |title=DART Sets Sights on Asteroid Target |url=http://www.nasa.gov/feature/dart-sets-sights-on-asteroid-target |access-date=10 September 2022 |website=NASA}}; {{cite web|date=22 November 2021|title=SpaceX ready for first launch with NASA interplanetary mission|url=https://spaceflightnow.com/2021/11/22/spacex-ready-for-first-launch-with-nasa-interplanetary-mission/|access-date=24 November 2021|publisher=Spaceflight Now}}; {{cite web |date=17 February 2021|title=DART Launch Moves to Secondary Window|url=https://www.nasa.gov/feature/dart-launch-moves-to-secondary-window|access-date=24 November 2021|publisher=NASA}} {{PD-notice}}; {{Cite news |date=26 September 2022 |title=Live: NASA to crash spacecraft into asteroid in trial to protect Earth from collisions |language=en-AU |work=ABC News |url=https://www.abc.net.au/news/2022-09-27/nasa-dart-mission-test-against-asteroid-hazards/101473242 |access-date=26 September 2022}}</ref>

== Mission history ==
[[Organization:NASA|NASA]] and the [[Organization:European Space Agency|European Space Agency]] (ESA) started with individual plans for missions to test [[Astronomy:Asteroid impact avoidance|asteroid deflection]] strategies, but by 2015, they struck a collaboration called [[Astronomy:AIDA (mission)|AIDA]] (Asteroid Impact and Deflection Assessment) involving two separate spacecraft launches that would work in synergy.<ref name="APL home">[http://dart.jhuapl.edu/ AIDA DART] Home page at APL</ref><ref name="Aida study 20153">{{Cite web |title=Asteroid Impact & Deflection Assessment (AIDA) study |url=http://www.esa.int/Our_Activities/Space_Engineering_Technology/NEO/Asteroid_Impact_Deflection_Assessment_AIDA_study |url-status=dead |archive-url=https://web.archive.org/web/20150607004851/http://www.esa.int/Our_Activities/Space_Engineering_Technology/NEO/Asteroid_Impact_Deflection_Assessment_AIDA_study |archive-date=7 June 2015}}</ref><ref name="Home APL">[http://dart.jhuapl.edu/Mission/index.php DART] at Applied Physics Laboratory Johns Hopkins University</ref> Under that proposal, the European Asteroid Impact Mission (AIM), would have launched in December 2020, and DART in July 2021. AIM would have orbited the larger asteroid to study its composition and that of its moon. DART would then kinetically impact the asteroid's moon on 26 September 2022, during a close approach to Earth.<ref name="Aida study 20153" />

The AIM orbiter was however canceled, then replaced by [[Astronomy:Hera (space mission)|Hera]] which plans to start observing the asteroid four years after the DART impact. Live monitoring of the DART impact thus had to be obtained from ground-based [[Astronomy:Telescope|telescope]]s and [[Engineering:Radar|radar]].<ref name="DART home" /><ref name="Home APL" />

In June 2017, NASA approved a move from concept development to the preliminary design phase,<ref name="Brown-2017">{{Cite web |last1=Brown |first1=Geoff |last2=University |first2=Johns Hopkins |title=NASA plans to test asteroid deflection technique designed to prevent Earth impact |url=https://phys.org/news/2017-07-nasa-asteroid-deflection-technique-earth.html |website=phys.org}}</ref> and in August 2018 the start of the final design and assembly phase of the mission.<ref name="construction">[https://phys.org/news/2018-09-asteroid-deflection-mission-key-milestone.html Asteroid-deflection mission passes key development milestone] 7 September 2018</ref> On 11 April 2019, NASA announced that a SpaceX [[Engineering:Falcon 9|Falcon 9]] would be used to launch DART.<ref name="NASA_Falcon9">{{Cite web |date=12 April 2019 |title=NASA Awards Launch Services Contract for Asteroid Redirect Test Mission |url=https://www.nasa.gov/press-release/nasa-awards-launch-services-contract-for-asteroid-redirect-test-mission |access-date=12 April 2019 |publisher=NASA}} {{PD-notice}}</ref>

Satellite impact on a small Solar System body had already been implemented once, by NASA's {{Cvt|372|kg}} ''[[Engineering:Deep Impact (spacecraft)|Deep Impact]]'' space probe's impactor spacecraft and for a completely different purpose (analysis of the structure and composition of a comet). On impact, Deep Impact released 19 gigajoules of energy (the equivalent of 4.8 [[Ton|ton]]s of TNT),<ref>{{Cite web |title=NASA – Deep Impact's Impactor |url=https://www.nasa.gov/mission_pages/deepimpact/spacecraft/impactor.html |url-status=dead |archive-url=https://web.archive.org/web/20160623220100/http://www.nasa.gov/mission_pages/deepimpact/spacecraft/impactor.html |archive-date=23 June 2016 |website=nasa.gov}}</ref> and excavated a crater up to {{cvt|150|m}} wide.<ref>{{cite web |title=In Depth - Deep Impact (EPOXI) |url=https://solarsystem.nasa.gov/missions/deep-impact-epoxi/in-depth/ |website=NASA Solar System Exploration |access-date=11 October 2022}}</ref>

== Description ==

=== Spacecraft ===

The DART spacecraft was an impactor with a mass of {{cvt|610|kg}}<ref name="nasa-dart-oct2021">{{Cite web |date=28 October 2021 |title=Double Asteroid Redirection Test (DART) |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=DART |access-date=5 November 2021 |publisher=NASA}} {{PD-notice}}</ref> that hosted no scientific [[Engineering:Cargo|payload]] and had sensors only for navigation. The spacecraft cost US$330 million by the time it collided with Dimorphos in 2022.<ref name="Lost 1M kg" />

====Camera====
[[File:DRACO intergration to DART.jpg|thumb|DRACO camera]]

DART's navigation sensors included a [[Astronomy:Sun sensor|Sun sensor]], a [[Astronomy:Star tracker|star tracker]] called SMART Nav software (Small-body Maneuvering Autonomous Real Time Navigation),<ref name="dart.jhuapl.edu">{{Cite web |title=DART |url=https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php |access-date=20 May 2022 |website=dart.jhuapl.edu |language=en}}</ref> and a {{cvt|20|cm}} aperture camera called Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO). DRACO was based on the [[Astronomy:Long Range Reconnaissance Imager|Long Range Reconnaissance Imager]] (LORRI) onboard ''[[Astronomy:New Horizons|New Horizons]]'' spacecraft, and supported autonomous navigation to impact the asteroid's moon at its center. The optical part of DRACO was a Ritchey-Chrétien telescope with a [[Physics:Field of view|field of view]] of 0.29° and a [[Focal length|focal length]] of 2.6208 m (f/12.60). The spatial resolution of the images taken immediately before the impact was around 20 centimeters per pixel. The instrument had a mass of {{Cvt|8.66|kg}}.<ref name="dart-draco-design">{{Cite conference |last1=Fletcher |first1=Zachary |last2=Ryan |first2=Kyle |last3=Maas |first3=Bryan |last4=Dickman |first4=Joseph |last5=Hammond |first5=Randolph |last6=Bekker |first6=Dmitriy |last7=Nelson |first7=Tyler |last8=Mize |first8=James |last9=Greenberg |first9=Jacob |date=6 July 2018 |title=Design of the Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO) on the double asteroid redirection test (DART) |url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10698/2310136/Design-of-the-Didymos-reconnaissance-and-asteroid-camera-for-OpNav/10.1117/12.2310136.short?SSO=1 |conference=Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave |location=Austin, TX |publisher=Proceedings of SPIE 10698 |volume=106981X |doi=10.1117/12.2310136 |first10=Wendy |last10=Hunt |first11=Stephen |last11=Smee |first12=Nancy |last12=Chabot |first13=Andrew |last13=Cheng}}</ref>

The detector used in the camera was a CMOS image sensor measuring 2,560 × 2,160 <abbr>pixels</abbr>. The detector records the wavelength range from 0.4 to 1 micron (visible and near infrared). A [[Finance:Commercial off-the-shelf|commercial off-the-shelf]] CMOS detector was used instead of a custom [[Engineering:Charge-coupled device|charge-coupled device]] in LORRI. DRACO's detector performance actually met or exceeded that of LORRI because of the improvements in sensor technology in the decade separating the design of LORRI and DRACO.<ref>{{Cite web |last=Lakdawalla |first=Emily |date=22 September 2022 |title=DART Impact on Monday! |url=https://www.patreon.com/posts/dart-impact-on-72349462?utm_medium=social&utm_source=twitter&utm_campaign=postshare_creator |access-date=26 September 2022 |via=Patreon}}</ref> Fed into an onboard computer with software descended from anti-missile technology, the DRACO images helped DART autonomously guide itself to its crash.<ref name="LakdawallaS&T">{{Cite web |last=Lakdawalla |first=Emily |date=23 September 2022 |title=NASA's DART Mission to Impact Asteroid Monday |url=https://skyandtelescope.org/astronomy-news/nasas-dart-mission-to-impact-asteroid/ |access-date=26 September 2022 |website=Sky & Telescope |language=en-US}}</ref>

====Solar arrays====
{{multiple image
|image1 = Behind_the_Scenes_Inspecting_DART's_Roll_Out_Solar_Array_ROSA_Technology.webm
|image2 = Transformational Solar Array experiment on DART's Roll Out Solar Array (ROSA).png
|footer = The spacecraft's solar arrays used a [[Astronomy:Roll Out Solar Array|Roll Out Solar Array]] (ROSA) design, that was tested on the [[Astronomy:International Space Station|International Space Station]] (ISS) in June 2017 as part of [[Astronomy:Expedition 52|Expedition 52]].<ref>{{Cite news |last=Talbert |first=Tricia |date=30 June 2017 |title=Double Asteroid Redirection Test (DART) Mission |publisher=NASA |url=https://www.nasa.gov/planetarydefense/dart |access-date=21 January 2018}} {{PD-notice}}</ref>
}}

Using ROSA as the structure, a small portion of the DART solar array was configured to demonstrate [[Astronomy:Roll Out Solar Array|Transformational Solar Array]] technology, which has very-high-efficiency SolAero Inverted Metamorphic (IMM) solar cells and reflective concentrators providing three times more power than current other solar array technology.<ref>{{citation|url=https://www.youtube.com/watch?v=UmSdzC93H7c|title=Behind the Scenes: Inspecting DART's Roll-Out Solar Array (ROSA) Technology|access-date=13 August 2021}}; {{Cite web |title=DART has a solar array experiment called transformational solar array on its roll out solar array panel |url=https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php |url-status=live |archive-url=https://web.archive.org/web/20191223144842/https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php |archive-date=23 December 2019 |access-date=13 August 2021 |website=dart.jhuapl.edu}}</ref>

====Antenna====
The DART spacecraft was the first spacecraft to use a new type of high-gain communication antenna, a Spiral Radial Line Slot Array (RLSA). The circularly-polarized antenna operated at the [[Physics:X band|X-band]] [[Astronomy:NASA Deep Space Network|NASA Deep Space Network]] (NASA DSN) frequencies of 7.2 and 8.4 [[Hertz|GHz]], and had a gain of 29.8 dBi on downlink and 23.6 dBi on uplink. The fabricated antenna in a flat and compact shape exceeded the given requirements and was tested through environments resulting in a [[Engineering:Technology readiness level|TRL]]-6 design.<ref>{{Cite book |last=Bray |first=Matthew |title=2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting |year=2020 |isbn=978-1-7281-6670-4 |pages=379–380 |chapter=A Spiral Radial Line Slot Array Antenna for NASA's Double Asteroid Redirection Test (DART) |doi=10.1109/IEEECONF35879.2020.9330400 |s2cid=231975847}}</ref>[[File:NASA NEXT Ion thruster.712983main NEXT LDT Thrusterhi-res full.jpg|thumb|NASA's Evolutionary Xenon Thruster ([[Engineering:NEXT (ion thruster)|NEXT]])]]

====Ion thruster====

DART demonstrated the [[Engineering:NEXT (ion thruster)|NEXT gridded ion thruster]], a type of [[Engineering:Solar electric propulsion|solar electric propulsion]].<ref name="DART home">[https://www.nasa.gov/planetarydefense/dart Planetary Defense: Double Asteroid Redirection Test (DART) Mission] NASA 2017 {{PD-notice}}</ref><ref>{{Cite book |last=Kantsiper |first=Brian |title=2017 IEEE Aerospace Conference |year=2017 |isbn=978-1-5090-1613-6 |pages=1–7 |chapter=The Double Asteroid Redirection Test (DART) mission electric propulsion trade |doi=10.1109/AERO.2017.7943736 |s2cid=43072949}}</ref> It was powered by {{cvt|22|m2}} solar arrays to generate the ~3.5&nbsp;kW needed to power the NASA Evolutionary [[Chemistry:Xenon|Xenon]] Thruster–Commercial (NEXT-C) engine.<ref name="Power">{{Cite book |last1=Adams |first1=Elena |title=2019 IEEE Aerospace Conference |last2=Oshaughnessy |first2=Daniel |last3=Reinhart |first3=Matthew |last4=John |first4=Jeremy |last5=Congdon |first5=Elizabeth |last6=Gallagher |first6=Daniel |last7=Abel |first7=Elisabeth |last8=Atchison |first8=Justin |last9=Fletcher |first9=Zachary |year=2019 |isbn=978-1-5386-6854-2 |pages=1–11 |chapter=Double Asteroid Redirection Test: The Earth Strikes Back |doi=10.1109/AERO.2019.8742007 |last10=Chen |first10=Michelle |last11=Heistand |first11=Christopher |last12=Huang |first12=Philip |last13=Smith |first13=Evan |last14=Sibol |first14=Deane |last15=Bekker |first15=Dmitriy |last16=Carrelli |first16=David |s2cid=195222414}}</ref> Early tests of the ion thruster revealed a reset mode that induced higher current (100 A) in the spacecraft structure than expected (25 A). It was decided not to use the ion thruster further as the mission could be accomplished without it, using conventional thrusters fueled by the 110 pounds of [[Chemistry:Hydrazine|hydrazine]] onboard.<ref>{{cite web |title=Impactor Spacecraft |url=https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php |website=DART |publisher=The Johns Hopkins University |access-date=24 November 2022}}</ref> However, the ion thrusters remained available if needed to deal with contingencies, and had DART missed its target, the ion system could have returned DART to Dimorphos two years later.<ref>[https://www.youtube.com/watch?v=fsZo1cxMqck NASA's DART Mission Post-Asteroid-Impact News Briefing], 26 September 2022, 8pm EDT, at 27 minutes</ref>

=== Secondary spacecraft ===
[[File:LICIACube CubeSat a companion satellite of Dart Spacecraft.jpg|thumb|upright=1.0|right|LICIACube CubeSat, a companion satellite of the DART spacecraft]]
{{Main Article|Astronomy:LICIACube}}

The [[Organization:Italian Space Agency|Italian Space Agency]] (ASI) contributed a secondary spacecraft called [[Astronomy:LICIACube|LICIACube]] (''Light Italian CubeSat for Imaging of Asteroids''), a small [[Engineering:CubeSat|CubeSat]] that piggybacked with ''DART'' and separated on 11 September 2022, 15 days before impact. It acquired images of the impact and ejecta as it drifted past the asteroid.<ref name="DART Home LICIA">[http://dart.jhuapl.edu/News-and-Resources/blog.php?id=20180927 Asteroids have been hitting the Earth for billions of years. In 2022, we hit back.] {{webarchive|url=https://web.archive.org/web/20181031133108/http://dart.jhuapl.edu/News-and-Resources/blog.php?id=20180927 |date=31 October 2018}} Andy Rivkin, The Johns Hopkins University Applied Physics Laboratory, 27 September 2018</ref><ref name="esa20181220">{{Cite web |last1=Kretschmar |first1=Peter |last2=Küppers |first2=Michael |date=20 December 2018 |title=The CubeSat Revolution |url=https://www.cosmos.esa.int/documents/13611/1603502/20181220_cubesats.pdf#page=34 |access-date=24 January 2019 |publisher=ESA}}</ref> LICIACube communicated directly with Earth, sending back images of the ejecta after the Dimorphos flyby.<ref name=LICIACuberef /><ref name="HeraWS2018">{{Cite web |last=Cheng |first=Andy |date=15 November 2018 |title=DART Mission Update |url=https://www.cosmos.esa.int/documents/1786001/1845930/4.+DART+Overview+%28A.+Cheng%29.pdf/da9935f1-74b7-9316-e9af-0fb2cc63197c |access-date=14 January 2019 |publisher=ESA}}</ref> LICIACube is equipped with two [[Physics:Camera|optical cameras]], dubbed LUKE and LEIA.<ref>{{Cite web |title=LICIACube |url=https://www.asi.it/en/planets-stars-universe/solar-system-and-beyond/liciacube/ |access-date=26 November 2021 |publisher=ASI}}</ref>

=== Effect of the impact on Dimorphos and Didymos ===
The spacecraft hit Dimorphos in the direction opposite to the asteroid's motion. Following the impact, the instantaneous orbital speed of Dimorphos therefore dropped slightly, which reduced the radius of its orbit around Didymos. The trajectory of Didymos was also modified, but in inverse proportion to the ratio of its mass to the much lower mass of Dimorphos. The actual velocity change and orbital shift depended on the topography and composition of the surface, among other things. The contribution of the recoil [[Physics:Momentum|momentum]] from the impact [[Astronomy:Ejecta|ejecta]] produces a poorly predictable "momentum enhancement" effect.<ref>{{Citation |title=WATCH: NASA Asteroid Redirection Test Media Briefing – Livestream |url=https://www.youtube.com/watch?v=EMwB0QERjEw |language=en |access-date=20 May 2022}}</ref> Before the impact, the momentum transferred by DART to the largest remaining fragment of the asteroid was estimated as up to 3–5 times the incident momentum, depending on how much and how fast material would be ejected from the impact crater. Obtaining accurate measurements of that effect was one of the mission's main goals and will help refine models of future impacts on asteroids.<ref>{{Cite journal |last1=Rivkin |first1=Andrew S. |last2=Chabot |first2=Nancy L. |last3=Stickle |first3=Angela M. |last4=Thomas |first4=Cristina A. |last5=Richardson |first5=Derek C. |last6=Barnouin |first6=Olivier |last7=Fahnestock |first7=Eugene G. |last8=Ernst |first8=Carolyn M. |last9=Cheng |first9=Andrew F. |last10=Chesley |first10=Steven |last11=Naidu |first11=Shantanu |date=25 August 2021 |title=The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements |journal=The Planetary Science Journal |volume=2 |issue=5 |page=173 |bibcode=2021PSJ.....2..173R |doi=10.3847/PSJ/ac063e |issn=2632-3338 |s2cid=237301576|doi-access=free }}</ref>

The DART impact excavated surface/subsurface materials of Dimorphos, leading to the formation of a crater and/or some magnitude of reshaping (i.e., shape change without significant mass loss). Some of the ejecta may eventually hit Didymos's surface. If the kinetic energy delivered to its surface was high enough, reshaping may have also occur in Didymos, given its near-rotational-breakup spin rate. Reshaping on either body would have modified their mutual gravitational field, leading to a reshaping-induced orbital period change, in addition to the impact-induced orbital period change. If left unaccounted for, this could later have led to an erroneous interpretation of the effect of the kinetic deflection technique.<ref>{{Cite journal |last1=Nakano |first1=Ryota |last2=Hirabayashi |first2=Masatoshi |last3=Agrusa |first3=Harrison F. |last4=Ferrari |first4=Fabio |last5=Meyer |first5=Alex J. |last6=Michel |first6=Patrick |last7=Raducan |first7=Sabina D. |last8=Sánchez |first8=Paul |last9=Zhang |first9=Yun |date=5 July 2022 |title=NASA's Double Asteroid Redirection Test (DART): Mutual Orbital Period Change Due to Reshaping in the Near-Earth Binary Asteroid System (65803) Didymos |journal=The Planetary Science Journal |language=en |volume=3 |issue=7 |pages=148 |doi=10.3847/PSJ/ac7566 |bibcode=2022PSJ.....3..148N |s2cid=250327233 |issn=2632-3338|doi-access=free |hdl=11311/1223308 |hdl-access=free }}</ref>

===Observations of the impact===
[[File:Telescopes observing DART's impact.png|thumb|Telescopes observing DART's impact]]
[[File:Aftermath of DART Collision with Dimorphos Captured by SOAR Telescope (noirlab2223a).jpg|thumb|[[Astronomy:Southern Astrophysical Research Telescope|SOAR telescope]] shows the vast plume of dust and debris blasted from the surface of the asteroid Dimorphos]]
DART's companion LICIACube,<ref>[https://twitter.com/LICIACube LICIACube Twitter feed]</ref><ref name=LICIACuberef>{{cite news|url=https://gizmodo.com/liciacube-images-dart-asteroid-impact-1849585958 |title=First Asteroid Impact Images from DART's Companion Show Tentacle-Like Debris Plume|author=George Dvorsky|date=September 27, 2022|publisher=Gizmodo}}</ref> the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]], [[Astronomy:James Webb Space Telescope|James Webb Space Telescope]], and the Earth-based [[Astronomy:Asteroid Terrestrial-impact Last Alert System|ATLAS observatory]] all detected the ejecta plume from the DART impact.<ref>[https://twitter.com/fallingstarIfA ATLAS twitter feed]</ref><ref name=atlasref>{{cite news|url=https://gizmodo.com/telescopes-capture-dart-asteroid-impact-1849585394|title=Ground Telescopes Capture Jaw-Dropping Views of DART Asteroid Impact|
quote=Telescopes around the world honed in on the historic collision, revealing a surprisingly large and bright impact plume.|author=George Dvorsky|date=September 27, 2022|publisher=Gizmodo}}</ref> On September 26, [[Astronomy:Southern Astrophysical Research Telescope|SOAR]] observed the visible impact trail to be over 10,000 km long.<ref>{{cite news |last1=Strickland |first1=Ashley |title=Comet-like debris trail spotted after spacecraft crashes into asteroid |url=https://www.cnn.com/2022/10/04/world/nasa-dart-debris-trail-scn/index.html |access-date=6 October 2022 |work=CNN |date=4 October 2022 |language=en}}</ref> Initial estimates of the change in binary orbit period were expected within a week and with the data released by LICIACube.<ref>{{Cite web |title=DART: Asteroid – eoPortal Directory – Satellite Missions |url=https://directory.eoportal.org/web/eoportal/satellite-missions/d/dart-asteroid |access-date=24 November 2021 |website=directory.eoportal.org}}</ref> DART's mission science depends on careful Earth-based monitoring of the orbit of Dimorphos over the subsequent days and months. Dimorphos was too small and too close to Didymos for almost any observer to see directly, but its orbital geometry is such that it transits Didymos once each orbit and then passes behind it half an orbit later. Any observer that can detect the Didymos system therefore sees the system dim and brighten again as the two bodies cross. 

The impact was planned for a moment when the distance between Didymos and Earth is at a minimum, permitting many telescopes to make observations from many locations. The asteroid was near opposition and visible high in the night sky well into 2023.<ref name="Lakwadalla-DART"/> The change in Dimorphos's orbit around Didymos was detected by [[Astronomy:Optical telescope|optical telescope]]s watching mutual [[Astronomy:Eclipse|eclipse]]s of the two bodies through [[Astronomy:Photometry|photometry]] on the Dimorphos-Didymos pair. In addition to radar observations, they confirmed that the impact shortened Dimorphos' orbital period by 32 minutes.<ref name="DartUpdateNASA">{{cite web |last1=Nelson |first1=Bill |last2=Saccoccia |first2=Giorgio |title=Update on DART Mission to Asteroid Dimorphos (NASA News Conference) |url=https://www.youtube.com/watch?v=Zhzn0U2m5wQ |website=YouTube |access-date=11 October 2022 |language=en}}</ref> Based on the shortened binary orbital period, the instantaneous reduction in Dimorphos' velocity component along its orbital track was determined, which indicated that substantially more momentum was transferred to Dimorphos from the escaping impact ejecta than from the impact itself. In this way, the DART kinetic impact was highly effective in deflecting Dimorphos.<ref name="Nature March2023">{{cite journal | vauthors=Cheng AF, Agrusa HF, Barbee BW, Meyer AJ | display-authors =3|title=Momentum transfer from the DART mission kinetic impact on asteroid Dimorphos |journal=Nature |date=1 March 2023 | volume =616| issue =7957| pages =457–460|doi=10.1038/s41586-023-05878-z | pmid =36858075| pmc =10115652| arxiv =2303.03464| bibcode =2023Natur.616..457C| s2cid =257282972}}</ref>

=== Follow-up mission ===
In a collaborating project, the [[Organization:European Space Agency|European Space Agency]] is developing ''[[Astronomy:Hera (space mission)|Hera]]'', a spacecraft that will be launched to Didymos in 2024<ref name="DART Home LICIA" /><ref name="Hera approval">[https://room.eu.com/news/hera-mission-is-approved-as-esa-receives-biggest-ever-budget Hera mission is approved as ESA receives biggest ever budget] Kerry Hebden ''Room Space Journal'' 29 November 2019</ref><ref name="nsf201901">{{Cite news |last=Bergin |first=Chris |date=7 January 2019 |title=Hera adds objectives to planetary defense test mission |publisher=NASASpaceflight.com |url=https://www.nasaspaceflight.com/2019/01/hera-objectives-planetary-defense-mission/ |access-date=11 January 2019}}</ref> and arrive in 2026<ref>{{Cite journal|title=The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos|first1=Patrick|last1=Michel|first2=Michael|last2=Küppers|first3=Adriano Campo|last3=Bagatin|first4=Benoit|last4=Carry|first5=Sébastien|last5=Charnoz|first6=Julia de|last6=Leon|first7=Alan|last7=Fitzsimmons|first8=Paulo|last8=Gordo|first9=Simon F.|last9=Green|first10=Alain|last10=Hérique|first11=Martin|last11=Juzi|first12=Özgür|last12=Karatekin|first13=Tomas|last13=Kohout|first14=Monica|last14=Lazzarin|first15=Naomi|last15=Murdoch|first16=Tatsuaki|last16=Okada|first17=Ernesto|last17=Palomba|first18=Petr|last18=Pravec|first19=Colin|last19=Snodgrass|first20=Paolo|last20=Tortora|first21=Kleomenis|last21=Tsiganis|first22=Stephan|last22=Ulamec|first23=Jean-Baptiste|last23=Vincent|first24=Kai|last24=Wünnemann|first25=Yun|last25=Zhang|first26=Sabina D.|last26=Raducan|first27=Elisabetta|last27=Dotto|first28=Nancy|last28=Chabot|first29=Andy F.|last29=Cheng|first30=Andy|last30=Rivkin|first31=Olivier|last31=Barnouin|first32=Carolyn|last32=Ernst|first33=Angela|last33=Stickle|first34=Derek C.|last34=Richardson|first35=Cristina|last35=Thomas|first36=Masahiko|last36=Arakawa|first37=Hirdy|last37=Miyamoto|first38=Akiko|last38=Nakamura|first39=Seiji|last39=Sugita|first40=Makoto|last40=Yoshikawa|first41=Paul|last41=Abell|first42=Erik|last42=Asphaug|first43=Ronald-Louis|last43=Ballouz|first44=William F.|last44=Bottke|first45=Dante S.|last45=Lauretta|first46=Kevin J.|last46=Walsh|first47=Paolo|last47=Martino|first48=Ian|last48=Carnelli|date=15 July 2022|journal=The Planetary Science Journal|volume=3|issue=7|pages=160|doi=10.3847/PSJ/ac6f52|bibcode=2022PSJ.....3..160M |s2cid=250599919 |doi-access=free|hdl=10045/125568|hdl-access=free}}</ref><ref>[https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4372&context=smallsat The Juventas CubeSat in Support of ESA's Hera Mission to the Asteroid Didymos.] Hannah R. Goldberg, Özgür Karatekin, Birgit Ritter, Alain Herique, Paolo Tortora, Claudiu Prioroc, Borja Garcia Gutierrez, Paolo Martino, Ian Carnelli. 33rd Annual AIAA/USU Conference on Small Satellites.</ref> to do a detailed reconnaissance and assessment.<ref name="nsf201901" /> ''Hera'' would carry two [[Engineering:CubeSat|CubeSat]]s, ''Milani'' and ''Juventas''.<ref name="nsf201901" />

=== AIDA mission architecture ===
{{excerpt|AIDA (international space cooperation)|AIDA mission architecture|hat=no}}

== Mission profile ==

=== Target asteroid ===
[[File:65803 didymos model.png|thumb|upright=1.0|right|Pre-impact shape model of ''Didymos'' and its satellite ''Dimorphos'', based on photometric light curve and radar data]]

The mission's target was Dimorphos in 65803 Didymos system, a [[Astronomy:Binary asteroid|binary asteroid]] system in which one asteroid is orbited by a smaller one. The primary asteroid (Didymos A) is about {{cvt|780|m}} in diameter; the asteroid moon Dimorphos (Didymos B) is about {{cvt|160|m}} in diameter in an orbit about {{cvt|1|km}} from the primary.<ref name="DART home" /> The [[Physics:Mass|mass]] of the Didymos system is estimated at 528&nbsp;billion kg, with Dimorphos comprising 4.8&nbsp;billion kg of that total.<ref name="nasa-dart-oct2021" /> Choosing a binary asteroid system is advantageous because changes to Dimorphos's velocity can be measured by observing when Dimorphos subsequently passes in front of its companion, causing a dip in light that can be seen by Earth telescopes. Dimorphos was also chosen due to its appropriate size; it is in the size range of asteroids that one would want to deflect, were they on a collision course with Earth. In addition, the binary system was relatively close to the Earth in 2022, at about {{convert|7|e6mi|order=flip|abbr=unit|0}}.<ref>{{Cite news |date=23 November 2021 |title=Seen the film Armageddon? NASA's aiming to smash an asteroid off course in real life |language=en-AU |work=Australian Broadcasting Corporation (ABC) |url=https://www.abc.net.au/news/science/2021-11-24/nasa-dart-mission-deflect-asteroid-armageddon/100574146 |access-date=24 September 2022}}</ref> The Didymos system is not an Earth-crossing asteroid, and there is no possibility that the deflection experiment could create an impact hazard.<ref name="P. Michel">{{Cite journal |last1=Michel |first1=P. |last2=Cheng |first2=A. |last3=Carnelli |first3=I. |last4=Rivkin |first4=A. |last5=Galvez |first5=A. |last6=Ulamec |first6=S. |last7=Reed |first7=C. |last8=AIDA Team |date=8 January 2015 |title=AIDA: Asteroid impact and deflection assessment mission under study at ESA and NASA |url=https://elib.dlr.de/95095/ |journal=Spacecraft Reconnaissance of Asteroid and Comet Interiors |volume=1829 |page=6008 |bibcode=2015LPICo1829.6008M}}</ref>  On 4&nbsp;October 2022, Didymos made an Earth approach of {{convert|10.6|e6km|e6mi|abbr=unit}}.<ref>{{cite report |title=65803&nbsp;Didymos |series=JPL Small-Body Database Browser |publisher=[[Organization:NASA|NASA]] / [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]] |url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2065803&view=OPC |access-date=2021-12-30 |via=ssd.jpl.nasa.gov}}</ref>

=== Preflight preparations ===
[[File:DART inside the payload fairing (KSC-20211116-PH-EGW01 0001).jpg|thumb|upright=0.8|left|DART being encapsulated in the Falcon 9 [[Engineering:Payload fairing|payload fairing]] on 16 November 2021]]

Launch preparations for DART began on 20 October 2021, as the spacecraft began fueling at Vandenberg Space Force Base (VSFB) in California.<ref name="sfnow">{{Cite web |date=20 October 2021 |title=Spacecraft for asteroid deflection experiment ready for fueling at Vandenberg |url=https://spaceflightnow.com/2021/10/20/spacecraft-for-asteroid-deflection-experiment-ready-for-fueling-at-vandenberg/ |access-date=5 November 2021 |publisher=Spaceflight Now}}</ref> The spacecraft&nbsp;arrived at Vandenberg in early October&nbsp;2021 after a cross-country drive. DART team members prepared the spacecraft for flight, testing the spacecraft's mechanisms and electrical system, wrapping the final parts in multilayer insulation blankets and practicing the launch sequence from both the launch site and the mission operations center at APL.&nbsp;DART headed to the SpaceX Payload Processing Facility on VSFB on 26 October 2021. Two days later, the team received the green light to fill DART's fuel tank with roughly {{cvt|50|kg}} of [[Chemistry:Hydrazine|hydrazine]] propellant for spacecraft maneuvers and attitude control. DART also carried about {{cvt|60|kg}} of [[Chemistry:Xenon|xenon]] for the NEXT-C ion engine. Engineers loaded the xenon before the spacecraft left APL in early October 2021.<ref name="Preps">{{Cite web |date=3 November 2021 |title=NASA's DART Preps for Launch in First Planetary Defense Test Mission |url=https://www.nasa.gov/feature/nasa-s-dart-prepares-for-launch-in-first-planetary-defense-test-mission |access-date=24 November 2021 |publisher=NASA}} {{PD-notice}}</ref>

Starting on 10 November 2021, engineers mated the spacecraft to the adapter that stacks on top of the SpaceX Falcon 9 launch vehicle. The Falcon 9 rocket without the payload fairing rolled for a static fire and later came back to the processing facility again where technicians with SpaceX installed the two halves of the fairing around the spacecraft over the course of two days, 16 and 17 November, inside the SpaceX Payload Processing Facility at Vandenberg Space Force Base and the ground teams completed a successful Flight Readiness Review later that week with the fairing then attached to the rocket.<ref>{{Cite web |title=NASA's DART Spacecraft Secured in Payload Fairing, Flight Readiness Review Complete – Double Asteroid Redirection Test (DART) Mission |url=https://blogs.nasa.gov/dart/2021/11/22/nasas-dart-spacecraft-secured-in-payload-fairing-flight-readiness-review-complete/ |access-date=24 November 2021 |website=blogs.nasa.gov|date=22 November 2021 }} {{PD-notice}}</ref>

A day&nbsp;before launch, the launch vehicle rolled out of the hangar and onto the launch pad at Vandenberg Space Launch Complex 4 (SLC-4E); from there, it lifted off to begin DART's journey to the Didymos system and it propelled the spacecraft into space.<ref name="Preps" />

{{-}}
=== Launch ===
{{multiple image
| direction = vertical
| image1= DART Launch (NHQ202111230022).jpg
| caption1= Liftoff of Falcon 9 with DART.
| image2= DART-Separation-from-Second-Stage 01.jpg
| caption2= DART separation from second stage
}}
The DART spacecraft was launched on 24 November 2021, at 06:21:02 [[Physics:Coordinated Universal Time|UTC]].

Early planning suggested that DART was to be deployed into a [[Astronomy:High Earth orbit|high-altitude]], high-[[Astronomy:Orbital eccentricity|eccentricity]] [[Astronomy:Geocentric orbit|Earth orbit]] designed to avoid the [[Astronomy:Moon|Moon]]. In such a scenario, DART would use its low-thrust, high-[[Physics:Specific impulse|efficiency]] [[Engineering:NEXT (ion thruster)|NEXT ion engine]] to slowly escape from its high Earth orbit to a slightly inclined near-Earth solar orbit, from which it would maneuver onto a collision trajectory with its target. But because DART was launched as a dedicated [[Engineering:Falcon 9|Falcon 9]] mission, the payload along with Falcon 9's second stage was placed directly on an Earth escape trajectory and into [[Astronomy:Heliocentric orbit|heliocentric orbit]] when the second stage reignited for a second engine startup or escape burn. Thus, although DART carries a first-of-its-kind electric thruster and plenty of xenon fuel, Falcon 9 did almost all of the work, leaving the spacecraft to perform only a few trajectory-correction burns with simple chemical thrusters as it homed in on Didymos's moon Dimorphos.<ref>{{Cite journal |last1=Atchison |first1=Justin A. |last2=Ozimek |first2=Martin T. |last3=Kantsiper |first3=Brian L. |last4=Cheng |first4=Andrew F. |date=1 June 2016 |title=Trajectory options for the DART mission |url=https://www.sciencedirect.com/science/article/pii/S0094576515303040 |journal=Acta Astronautica |series=Special Section: Selected Papers from the International Workshop on Satellite Constellations and Formation Flying 2015 |volume=123 |pages=330–339 |bibcode=2016AcAau.123..330A |doi=10.1016/j.actaastro.2016.03.032 |issn=0094-5765}}</ref>

===Transit===
[[File:Animation of DART trajectory around Sun.gif|thumb|upright=1.0|right|Animation of DART's trajectory<br />{{legend2|magenta|DART}}{{·}}{{legend2|lime|[[Astronomy:65803 Didymos|65803 Didymos]]}}{{·}}{{legend2|Royalblue|Earth}}{{·}}{{legend2|yellow|Sun}}{{·}}{{legend2|cyan|{{mpl|2001 CB|21}}}}{{·}}{{legend2|gold|3361 Orpheus}}]]

The transit phase before impact lasted about 9 months. During its interplanetary travel, the DART spacecraft made a distant [[Engineering:Flyby (spaceflight)|flyby]] of the 578-meter-diameter near-Earth asteroid {{mpl|(138971) 2001 CB|21}} in March 2022.<ref>{{Cite web |title=Double Asteroid Redirection Test (DART) |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2021-110A |access-date=25 September 2022 |website=NASA Space Science Data Coordinated Archive |publisher=NASA}}; {{cite web|title=Asteroids have been hitting the Earth for billions of years. In 2022, we hit back.|url=https://dart.jhuapl.edu/News-and-Resources/article.php?id=20180927|first=Andy|last=Rivkin|work=DART|publisher=Johns Hopkins University Applied Physics Laboratory|date=27 September 2018|accessdate=25 September 2022}}</ref> DART passed {{convert|0.117|AU|e6km e6mi|abbr=unit}} from {{mp|2001 CB|21}} in its closest approach on 2 March 2022.<ref name="DART-CB21-horizons">{{Cite web |title=JPL Horizons On-Line Ephemeris for 138971 (2001 CB21) on 2022-Mar-01 to 2022-Mar-03 |url=https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%27138971%27&OBJ_DATA=%27YES%27&MAKE_EPHEM=%27YES%27&EPHEM_TYPE=%27OBSERVER%27&CENTER=%27500@-135%27&START_TIME=%272022-03-01%27&STOP_TIME=%272022-03-03%27&STEP_SIZE=%271h%27&QUANTITIES=%271,9,20,23%27&RANGE_UNITS=%27KM%27 |access-date=28 September 2022 |website=[[Astronomy:JPL Horizons On-Line Ephemeris System|JPL Horizons On-Line Ephemeris System]] |publisher=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]}} Ephemeris Type: Observer. Target Body: 138971 (2001 CB21). Observer Location: 500@-135 (DART Spacecraft).</ref>

DART's DRACO camera opened its aperture door and took its [[Astronomy:First light|first light]] image of some stars on 7 December 2021, when it was {{convert|2|e6mi|order=flip|abbr=unit|0}} away from Earth.<ref name="FirstLight">{{Cite web |last=Talbert |first=Tricia |date=22 December 2021 |title=NASA's DART Captures One of Night Sky's Brightest Stars |url=https://www.nasa.gov/feature/with-its-single-eye-nasa-s-dart-returns-first-images-from-space/ |access-date=25 September 2022 |publisher=NASA}}</ref> The stars in DRACO's first light image were used as calibration for the camera's pointing before it could be used to image other targets.<ref name="FirstLight" /> On 10 December 2021, DRACO imaged the [[Astronomy:Open cluster|open cluster]] [[Astronomy:Messier 38|Messier 38]] for further optical and [[Astronomy:Photometry|photometric]] calibration.<ref name="FirstLight" />

On 27 May 2022, DART observed the bright star [[Astronomy:Vega|Vega]] with DRACO to test the camera's optics with scattered light.<ref name="Vega">{{Cite web |last=Talbert |first=Tricia |date=17 June 2022 |title=NASA's DART Captures One of Night Sky's Brightest Stars |url=https://www.nasa.gov/feature/nasa-s-dart-captures-one-of-night-sky-s-brightest-stars |access-date=25 September 2022 |publisher=NASA}}</ref> On 1 July and 2 August 2022, DART's DRACO imager observed [[Astronomy:Jupiter|Jupiter]] and its moon [[Astronomy:Europa (moon)|Europa]] emerging from behind the planet, as a performance test for the SMART Nav tracking system to prepare for the Dimorphos impact.<ref name="JupiterSMARTNav">{{Cite web |last=Talbert |first=Tricia |date=22 September 2022 |title=DART Tests Autonomous Navigation System Using Jupiter and Europa |url=https://www.nasa.gov/feature/dart-tests-autonomous-navigation-system-using-jupiter-and-europa/ |access-date=25 September 2022 |publisher=NASA}}</ref>

===Course of the impact===
Two months before the impact, on 27 July 2022, the DRACO camera detected the Didymos system from approximately {{convert|32|e6km|abbr=unit}} away and started refining its trajectory. The [[Astronomy:LICIACube|LICIACube]] [[Engineering:Nanosatellite|nanosatellite]] was released on 11 September 2022, 15 days before the impact.<ref name="LICIACube-release">{{Cite web |last=Keeter |first=Bill |date=14 September 2022 |title=DART's Small Satellite Companion Takes Flight Ahead of Impact |url=https://www.nasa.gov/feature/dart-s-small-satellite-companion-takes-flight-ahead-of-impact |access-date=25 September 2022 |publisher=NASA}}</ref> Four hours before impact, some {{cvt|90000|km}} away, DART began to operate in complete autonomy under control of its SMART Nav [[Engineering:Guidance system|guidance system]]. Three hours before impact, DART performed an inventory of objects near the target. Ninety minutes before the collision, when DART was {{cvt|38000|km}} away from Dimorphos, the final trajectory was established.<ref>{{Cite web |date=26 September 2022 |title=NASA's DART Mission Hits Asteroid in First-Ever Planetary Defense Test |url=https://www.nasa.gov/press-release/nasa-s-dart-mission-hits-asteroid-in-first-ever-planetary-defense-test}}</ref> When DART was {{cvt|24000|km}} away Dimorphos became discernible (1.4 pixels) through the DRACO camera which then continued to capture images of the asteroid's surface and transmit them in real-time.<ref name="unoosa.org">{{cite web|first=T.|last=Statler|title=Session 3: DART|url=https://www.unoosa.org/documents/pdf/smpag/PDC2021_Presentation_Day1/IAA-PDC-21-03-MASTERFILE.pdf|access-date=November 5, 2022|publisher=7th IAA Planetary Defense Conference}}</ref>

DRACO was the only instrument able to provide a detailed view of Dimorphos' surface. The use of DART's thrusters caused vibrations throughout the spacecraft and solar panels, resulting in blurred images. To ensure sharp images, the last trajectory correction was executed 4 minutes before impact and the thrusters were deactivated afterwards.<ref name="unoosa.org" />

[[File:Dart impact replay.webm|thumb|upright=1.2|Compiled timelapse of DART's final 5.5 minutes until impact]]

The last full image, transmitted two seconds before impact, has a spatial resolution of about 3 centimeters per pixel. The impact took place on 26 September 2022, at 23:14 [[UTC]].<ref name="spacecom-impact-time">{{Cite web |last=Malik |first=Taliq |date=23 September 2022 |title=DART asteroid crash: What time will NASA probe hit Dimorphos on Sept. 26? |url=https://www.space.com/dart-asteroid-impact-crash-what-time |access-date=25 September 2022 |website=Space.com}}</ref>

The head-on impact of the {{cvt|500|kg}}<ref name="spacecraft at APL">[http://dart.jhuapl.edu/The-Spacecraft/index.php DART: Home page at APL] {{Webarchive|url=https://web.archive.org/web/20180510132556/http://dart.jhuapl.edu/The-Spacecraft/index.php|date=10 May 2018}} DART Spacecraft APL 2017</ref> DART spacecraft at {{cvt|6.6|km/s}}<ref>{{Cite web |year=2021 |title=Impactor Spacecraft |url=https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php |access-date=18 February 2021 |publisher=NASA}} {{PD-notice}}; {{cite news |last1=Andone |first1=Dakin |date=25 July 2017 |title=NASA unveils plan to test asteroid defense technique |publisher=CNN |url=http://edition.cnn.com/2017/07/01/us/nasa-asteroid-defense-trnd/index.html |access-date=25 July 2017}}</ref> likely imparted an energy of about 11 gigajoules, the equivalent of about three [[Physics:TNT equivalent|tonnes of TNT]],<ref>{{Cite web |last=Soldini |first=Stefania |title=Can we really deflect an asteroid by crashing into it? Nobody knows, but we are excited to try |url=http://theconversation.com/can-we-really-deflect-an-asteroid-by-crashing-into-it-nobody-knows-but-we-are-excited-to-try-190865 |access-date=23 September 2022 |website=The Conversation |date=21 September 2022 |language=en}}</ref> and was expected to [[Astronomy:Delta-v|reduce the orbital velocity]] of Dimorphos between {{val|1.75|u=cm/s}} and {{val|2.54|u=cm/s}}, depending on numerous factors such as material [[Earth:Porosity|porosity]].<ref>{{Cite web |last=Stickle |first=Angela |year=2022 |title=NASA's Double Asteroid Redirection Test Press Kit |url=https://dart.jhuapl.edu/News-and-Resources/files/DART-press-kit-web-FINAL.pdf|access-date=November 5, 2022|publisher=Johns Hopkins Applied Research Laboratory}}</ref> The reduction in Dimorphos's orbital velocity brings it closer to Didymos, resulting in the moon experiencing greater gravitational acceleration and thus a shorter orbital period.<ref name="Aida study 20153" /><ref name="P. Michel" /><ref name="Hadhazy-2017">{{Cite web |date=28 September 2017 |title=Course corrector |url=https://aerospaceamerica.aiaa.org/features/course-corrector/ |access-date=27 September 2022 |website=Aerospace America |language=en-US}}</ref> The orbital period reduction from the head-on impact serves to facilitate ground-based observations of Dimorphos. An impact to the asteroid's trailing side would instead increase its orbital period towards 12 hours and make it coincide with Earth's day and night cycle, which would limit any single ground-based telescope from observing all orbital phases of Dimorphos nightly.<ref name="Lakwadalla-DART">{{Cite web |last=Lakdawalla |first=Emily |date=22 September 2022 |title=DART Impact on Monday! |url=https://www.patreon.com/posts/dart-impact-on-72349462 |website=Patreon}}</ref>

[[File:DART-impact-SAAO-Lesedi-Mookodi.gif|thumb|left|DART impact and its corresponding plume as seen by using the Mookodi instrument on the SAAO's 1-m Lesedi telescope]]
The measured momentum enhancement factor (called beta) of  DART's impact of Dimorphos was 3.6, which means that the impact transferred roughly 3.6 times greater momentum than if the asteroid had simply absorbed the spacecraft and produced no ejecta at all – indicating the ejecta contributed more to moving the asteroid than the spacecraft did. This means one could use either a smaller impactor or shorter lead times for the same deflection. The value of beta depends on various factors, composition, density, porosity, etc. The goal is to use these results and modeling to infer what beta could be for another asteroid by observing its surface and possibly measuring its bulk density. Scientists estimate that DART’s impact displaced over {{cvt|1000000|kg}} of dusty ejecta into space – enough to fill six or seven rail cars. The tail of ejecta from Dimorphos created by the DART impact is at least {{cvt|30000|km}} long with a mass of at least {{cvt|1000|tonnes}}, and possibly up to 10 times that much.<ref>{{Cite web |last=Merzdorf |first=Jessica |date=2022-12-15 |title=Early Results from NASA's DART Mission |url=http://www.nasa.gov/feature/early-results-from-nasa-s-dart-mission |access-date=2022-12-16 |website=NASA}}</ref><ref>{{cite tweet|url=https://mobile.twitter.com/jeff_foust/status/1603478050917830657|title=One other note from the briefing: the tail of ejecta from Dimorphos created by the DART impact is at least 30,000 kilometers long, says Andy Rivkin of JHUAPL, with a mass of at least 1,000 metric tons, and possibly up to 10 times that much.|number=1603478050917830657|user=jeff_foust|date=December 15, 2022}}</ref>

[[File:Footprint of DART spacecraft over the spot where it impacted asteroid Dimorphos.jpg|thumb|Footprint of DART spacecraft over the spot where it impacted asteroid Dimorphos]]

The DART impact on the center of Dimorphos decreased the orbital period, previously 11.92 hours, by 33±1 minutes. This large change indicates the recoil from material excavated from the asteroid and ejected into space by the impact (known as ejecta) contributed significant momentum change to the asteroid, beyond that of the DART spacecraft itself. Researchers found the impact caused an instantaneous slowing in Dimorphos' speed along its orbit of about 2.7 millimeters per second — again indicating the recoil from ejecta played a major role in amplifying the momentum change directly imparted to the asteroid by the spacecraft. That momentum change was amplified by a factor of 2.2 to 4.9 (depending on the mass of Dimorphos), indicating the momentum change transferred because of ejecta production significantly exceeded the momentum change from the DART spacecraft alone.<ref name="nasa-march2023">{{cite web |last1=Furfaro |first1=Emily |title=NASA's DART Data Validates Kinetic Impact as Planetary Defense Method |url=https://www.nasa.gov/feature/nasa-s-dart-data-validates-kinetic-impact-as-planetary-defense-method |website=NASA |access-date=9 March 2023 |date=28 February 2023}} {{PD-notice}}</ref> While the orbital change was small, the change is in the velocity and over the course of years will accumulate to a large change in position.<ref>{{Cite web |title=NASA Pushes Through With Asteroid Deflection Mission That Could One Day Save Earth – Inquisitr |url=https://www.inquisitr.com/4346664/nasa-dart-asteroid-deflection-mission-save-earth-goes-into-design-phase/ |access-date=27 September 2022 |website=inquisitr.com|date=5 July 2017 }}</ref> For a hypothetical Earth-threatening body, even such a tiny change could be sufficient to mitigate or prevent an impact, if applied early enough. As the diameter of Earth is around 13,000 kilometers, a hypothetical asteroid impact could be avoided with as little of a shift as half of that (6,500 kilometers). A {{val|2|u=cm/s}} velocity change accumulates to that distance in approximately 10 years.<!-- 2*10^-5 km/s * 3600 s/h * 24h/day * 365 day/year = 630 km/year  -->

[[File:Two LICIACube LUKE images showing the ejecta morphology that were used to reduce the possible axis orientation solutions.webp|thumb|left|Dart Impact seen by LICIACube]]

By smashing into the asteroid DART made Dimorphos an [[Astronomy:Active asteroid|active asteroid]]. Scientists had proposed that some active asteroids are the result of impact events, but no one had ever observed the activation of an asteroid. The DART mission activated Dimorphos under precisely known and carefully observed impact conditions, enabling the detailed study of the formation of an active asteroid for the first time.<ref name="nasa-march2023"/><ref>{{cite journal |last1=Li |first1=Jian-Yang |last2=Hirabayashi |first2=Masatoshi |last3=Farnham |first3=Tony L. |last4=Sunshine |first4=Jessica M. |last5=Knight |first5=Matthew M. |last6=Tancredi |first6=Gonzalo |last7=Moreno |first7=Fernando |last8=Murphy |first8=Brian |last9=Opitom |first9=Cyrielle |last10=Chesley |first10=Steve |last11=Scheeres |first11=Daniel J. |last12=Thomas |first12=Cristina A. |last13=Fahnestock |first13=Eugene G. |last14=Cheng |first14=Andrew F. |last15=Dressel |first15=Linda |last16=Ernst |first16=Carolyn M. |last17=Ferrari |first17=Fabio |last18=Fitzsimmons |first18=Alan |last19=Ieva |first19=Simone |last20=Ivanovski |first20=Stavro L. |last21=Kareta |first21=Teddy |last22=Kolokolova |first22=Ludmilla |last23=Lister |first23=Tim |last24=Raducan |first24=Sabina D. |last25=Rivkin |first25=Andrew S. |last26=Rossi |first26=Alessandro |last27=Soldini |first27=Stefania |last28=Stickle |first28=Angela M. |last29=Vick |first29=Alison |last30=Vincent |first30=Jean-Baptiste |last31=Weaver |first31=Harold A. |last32=Bagnulo |first32=Stefano |last33=Bannister |first33=Michele T. |last34=Cambioni |first34=Saverio |last35=Bagatin |first35=Adriano Campo |last36=Chabot |first36=Nancy L. |last37=Cremonese |first37=Gabriele |last38=Daly |first38=R. Terik |last39=Dotto |first39=Elisabetta |last40=Glenar |first40=David A. |last41=Granvik |first41=Mikael |last42=Hasselmann |first42=Pedro H. |last43=Herreros |first43=Isabel |last44=Jacobson |first44=Seth |last45=Jutzi |first45=Martin |last46=Kohout |first46=Tomas |last47=La Forgia |first47=Fiorangela |last48=Lazzarin |first48=Monica |last49=Lin |first49=Zhong-Yi |last50=Lolachi |first50=Ramin |last51=Lucchetti |first51=Alice |last52=Makadia |first52=Rahil |last53=Epifani |first53=Elena Mazzotta |last54=Michel |first54=Patrick |last55=Migliorini |first55=Alessandra |last56=Moskovitz |first56=Nicholas A. |last57=Ormö |first57=Jens |last58=Pajola |first58=Maurizio |last59=Sánchez |first59=Paul |last60=Schwartz |first60=Stephen R. |last61=Snodgrass |first61=Colin |last62=Steckloff |first62=Jordan |last63=Stubbs |first63=Timothy J. |last64=Trigo-Rodríguez |first64=Josep M. |title=Ejecta from the DART-produced active asteroid Dimorphos |journal=Nature |date=1 March 2023 |volume=616 |issue=7957 |pages=452–456 |doi=10.1038/s41586-023-05811-4 |pmid=36858074 |pmc=10115637 |arxiv=2303.01700 |bibcode=2023Natur.616..452L |s2cid=257282549 |language=en |issn=1476-4687 |display-authors=3}}</ref> Observations show that Dimorphos lost approximately 1 million kilograms of mass as a result of the collision.<ref name="Lost 1M kg">{{cite journal |last1=Witze |first1=Alexandra |title=Asteroid lost 1 million kilograms as a result of the collision with DART spacecraft |journal=Nature |date=1 March 2023 |volume=615 |issue=7951 |pages=195 |doi=10.1038/d41586-023-00601-4 |pmid=36859675 |bibcode=2023Natur.615..195W |s2cid=257282080 |url=https://www.nature.com/articles/d41586-023-00601-4 |access-date=9 March 2023 |language=en}}</ref>
{{-}}

==== Sequence of operations for impact ====
{| class="wikitable alternance centre"
|-
! scope="col" |Date<br />(before impact)
! scope="col" |Distance from<br />Dimorphos<ref name="DART-Dimorphos-horizons">{{Cite web |title=JPL Horizons On-Line Ephemeris for Dimorphos on 2022-Sep-26 |url=https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%27Dimorphos%27&OBJ_DATA=%27YES%27&MAKE_EPHEM=%27YES%27&EPHEM_TYPE=%27OBSERVER%27&CENTER=%27500@-135%27&START_TIME=%272022-09-26%27&STOP_TIME=%272022-09-26%2023:15%27&STEP_SIZE=%271m%27&QUANTITIES=%271,9,20,23%27&RANGE_UNITS=%27KM%27 |access-date=25 September 2022 |website=[[Astronomy:JPL Horizons On-Line Ephemeris System|JPL Horizons On-Line Ephemeris System]] |publisher=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]}} Ephemeris Type: Observer. Target Body: Dimorphos. Observer Location: 500@-135 (DART Spacecraft).</ref>
! scope="col" |Raw image{{efn|The original raw DRACO images from DART were mirror flipped from reality. The images shown in the sequence of operations are uncorrected and show Didymos and Dimorphos as they appear on the DRACO detector.<ref>{{cite web|title=DART's Final Images Prior to Impact|url=https://www.nasa.gov/feature/dart-s-final-images-prior-to-impact|first=Tricia|last=Talbert|publisher=NASA|date=26 September 2022|accessdate=17 December 2022}}</ref>}}
! scope="col" |Events<ref name="PressKit">{{Cite web |title=Double Asteroid Redirection Test Press Kit |url=https://dart.jhuapl.edu/News-and-Resources/files/DART-press-kit-web-FINAL.pdf |publisher=Johns Hopkins University Applied Physics Laboratory}}</ref><ref name="unoosa">{{Cite conference |date= 26–30 April 2021 |title=Session 3: DART |url=https://www.unoosa.org/documents/pdf/smpag/PDC2021_Presentation_Day1/IAA-PDC-21-03-MASTERFILE.pdf |conference=7th IAA Planetary Defense Conference}}</ref>
|-
| align="center" |'''27 July 2022'''<br />(T-60 days)
| align="center" |{{cvt|38000000|km|mi}}
| align="center" |[[File:DART Sets Sights on Asteroid Target Composite of 243 images taken by DRACO on July 27, 2022, detecting Didymos.jpg|frameless|center]]
|The DRACO camera detects the Didymos system.
|-
| align="center" |'''11 September 2022'''<br />23:14 UTC<br />(T-15 days)
| align="center" |{{cvt|8000000|km|mi}}
| align="center" |
|Ejection of ''LICIACube'', which maneuvers to avoid crashing into the asteroid.<ref name="LICIACube-release" />
|-
| align="center" |'''26 September 2022'''<br />19:14 UTC<br />(T-4 hours)
| align="center" |{{cvt|89000|km|mi}}
| align="center" |
|Terminal phase—start of autonomous navigation with SMART Nav. DRACO locks onto Didymos since Dimorphos is not visible yet.<ref name="spacecom-impact-time" />
|-
| align="center" |22:14 UTC<br />(T-60 minutes)
| align="center" |{{Cvt|22000|km}}
| align="center" |[[File:DART-Didymos T-1 h.png|frameless|center]]
|The DRACO camera detects Dimorphos.
|-
| align="center" |22:54 UTC<br />(T-20 minutes)
| align="center" |{{Cvt|7500|km}}
|
|SMART Nav enters precision lock onto Dimorphos and DART begins thrusting toward Dimorphos.<ref name="spacecom-impact-time" />
|-
| align="center" |23:10 UTC<br />(T-4 minutes)
| align="center" |{{Cvt|1500|km}}
|[[File:Dart-five-minutes-impact.png|center|frameless]]
|Start of final course correction
|-
| align="center" |23:11 UTC<br />(T-2 minutes 30 seconds)
| align="center" |{{Cvt|920|km}}
|[[File:Both dart 0401929889 03770 01 iof imagedisplay-final.png|center|frameless]]
|Last image with both Didymos (lower-left) and Dimorphos entirely in frame is taken
|-
| align="center" |23:12 UTC<br />(T-2 minutes)
| align="center" |{{Cvt|740|km}}
|
|End of final course correction
|-
| align="center" |23:14 UTC<br />(T-20 seconds)
| align="center" |{{Cvt|130|km}}
|
|The photos taken reach the expected spatial resolution.
|-
| align="center" |23:14 UTC<br />(T-11 seconds)
| align="center" |{{Cvt|68|km}}
|[[File:All dimorphos dart 0401930040 12262 01 iof imagedisplay-final.png|frameless|center]]
|Last image showing all of Dimorphos by DART
|-
| align="center" |23:14 UTC<br />(T-3 seconds)
| align="center" |{{Cvt|18|km}}
|[[File:Dimorphos from DART aprox. 3 sec before impact.jpg|center|frameless]]
|
|-
| align="center" |23:14 UTC<br />(T-2 seconds)
| align="center" |{{Cvt|12|km}}
|[[File:Penultimate image of Dimorphos by DART.png|frameless|center]]
|Final complete image of Dimorphos transmitted. Resolution roughly 3 cm per pixel (~ 30m across).
|-
| align="center" |23:14 UTC<br />(T-1 second)
| align="center" |{{Cvt|6|km}}
|[[File:Dart 0401930049 43695 Final image.png|frameless|center]]
|Last partial image taken by DART before impact, transmission of the image was interrupted by the destruction of the spacecraft and all of its transmitting hardware. Resolution per pixel to be determined at a later date by analysis of image and timing.
|-
| align="center" |'''23:14 UTC<br />(T-0)'''
| align="center" |'''{{Cvt|0|km}}'''
|
|Impact Dimorphos (estimated impact velocity 6 kilometers/second)<ref>{{Cite web |date=30 June 2017 |title=NASA's First Asteroid Deflection Mission Enters Next Design Phase at Johns Hopkins APL |url=https://www.jhuapl.edu/PressRelease/170630 |access-date=28 September 2022 |publisher=Johns Hopkins University Applied Physics Laboratory}}</ref>
|-
| align="center" |23:17 UTC<br />{{nowrap|(T+2 min 45 s)<ref name="Lakwadalla-DART" />}}
| align="center" |'''{{Cvt|56.7|km}}'''
|[[File:Liciacube luke l0 1664234221 00000 01 rgb zoom flip.png|frameless|center]]
|Closest approach to Dimorphos by LICIACube.
|}
{{clear}}

== Gallery ==
<gallery mode="packed">
File:DART AnimatedSequence-2020 from launch to impact along with separation of LICIACube.webm|DART Mission animated video from launch to impact along with separation of LICIACube
File:Infographic of DART and Didymos Sizes.jpg|Size of DART and the two Didymos asteroids
File:This chart offers insight into data the DART team used to determine the orbit of Dimorphos after impact.jpg|This chart offers insight into data the DART team used to determine the orbit of Dimorphos after impact.
File:Webb and Hubble Capture Detailed Views of DART Impact (weic2215a).jpeg|Two of the great observatories, the NASA/ESA/CSA James Webb Space Telescope and the NASA/ESA Hubble Space Telescope, have captured views of a unique experiment to smash a spacecraft into a small asteroid. NASA’s Double Asteroid Redirection Test (DART).  <ref>{{cite news |url=https://esawebb.org/news/weic2215/|title=Webb and Hubble Capture Detailed Views of DART Impact. |date=October 20, 2023}}</ref> 
</gallery>

== See also ==
<!-- alphabetical order please WP:SEEALSO -->
<!-- please add a short description WP:SEEALSO, via {{subst:AnnotatedListOfLinks}} or {{Annotated link}} -->
* {{Annotated link |Asteroid impact avoidance}}
* {{Annotated link |B612 Foundation}}
* {{Annotated link |Deep Impact (spacecraft)}}
* {{Annotated link |Don Quijote (spacecraft)}}
* {{Annotated link |NEO Surveyor}}
* {{Annotated link |The Spaceguard Foundation}}
<!-- alphabetical order please WP:SEEALSO -->

== Notes ==
{{notelist}}

== References ==
{{Reflist}}

== External links ==
{{commons}}
* [https://www.nasa.gov/planetarydefense/dart Double Asteroid Redirection Test (DART) Mission] – NASA's Planetary Defense page on DART
* [https://blogs.nasa.gov/dart/2021/11/23/darts-mission-to-bump-an-asteroid/ DART’s Mission to Bump an Asteroid] – NASA Blog
* [https://www.youtube.com/watch?v=E0OUvEh3HWk NASA's DART Mission Launch, 24 November 2021] – Official Broadcast/Stream
* [https://www.youtube.com/watch?v=4RA8Tfa6Sck DART's Impact with Asteroid Dimorphos (Official NASA Broadcast)]

{{Planetary Missions Program Office|Solar System Exploration=y}}
{{Planetary defense}}
{{Asteroid spacecraft}}
{{Falcon rocket launches}}
{{Solar System probes}}


[[Category:Impactor spacecraft]]
[[Category:Missions to asteroids]]
[[Category:NASA space probes]]
[[Category:Solar System Exploration program]]
[[Category:SpaceX payloads contracted by NASA]]

{{Sourceattribution|Double Asteroid Redirection Test}}