View source for Engineering:MICROSCOPE (satellite)

{{Infobox spaceflight |auto=all
| name                  = MICROSCOPE

| mission_type          = Physics
| operator              = [[Organization:CNES|CNES]]
| COSPAR_ID             = 2016-025B
| SATCAT                = 41457
| website               = https://microscope.cnes.fr/en/
| mission_duration      = Planned: 2 years <br /> Elapsed: {{time interval|25 April 2016 21:02:13|show=ymd|sep=,}}

| spacecraft_bus        = [[Engineering:Myriade|Myriade]]<ref name="eoportal" />
| manufacturer          = [[Organization:CNES|CNES]]{{,}}[[Company:Airbus Defence and Space|Airbus]]
| launch_mass           = {{convert|330|kg|lb|0|abbr=on}}<ref name="eoportal" />
| dimensions            = {{convert|138|xx|104|xx|158|cm|in|abbr=on}}<ref name="eoportal" />
| power                 = 140 watts<ref name="eoportal" />

| launch_date           = {{start-date|25 April 2016, 21:02:13}}&nbsp;UTC<ref name="sfnow20160426" />
| launch_rocket         = [[Engineering:Soyuz-2|Soyuz-STA]] (VS-14)<ref name="ariane20160425" />
| launch_site           = [[Organization:Guiana Space Centre|Guiana Space Centre]] ELS<ref name="ariane20160425" />
| launch_contractor     = [[Company:Arianespace|Arianespace]]
| entered_service       = 2 May 2016<ref name="sfnow20160426" />

| disposal_type         = De-orbited
| deactivated           = 18 October 2018<ref name="EoM_CNES">{{cite web |title=End of mission for microscope - cnes’s satellite bows out with successful and innovative de-orbiting |url=https://presse.cnes.fr/en/end-mission-microscope-cness-satellite-bows-out-successful-and-innovative-de-orbiting |website=CNES.fr |accessdate=19 October 2018}}</ref>
| destroyed             = <!--when craft was destroyed (if other than by re-entry)-->
| last_contact          = <!--when last signal received if not decommissioned-->
| decay_date            = <!--when craft re-entered the atmosphere, not needed if it landed-->

| orbit_reference       = [[Astronomy:Geocentric orbit|Geocentric]]
| orbit_regime          = [[Astronomy:Low Earth orbit|Low Earth]]
| orbit_semimajor       = {{convert|7090.9|km|mi|abbr=on}}
| orbit_eccentricity    = 0.000167
| orbit_periapsis       = {{convert|711.6|km|mi|abbr=on}}
| orbit_apoapsis        = {{convert|713.9|km|mi|abbr=on}}
| orbit_inclination     = 98.23°
| orbit_period          = 99.03 minutes
| orbit_epoch           = 5 December 2016, 21:17:20&nbsp;UTC<ref name="heavens-above">{{cite web |url=http://heavens-above.com/orbit.aspx?satid=41457 |title=MICROSCOPE - Orbit |work=Heavens-Above |date=5 December 2016 |accessdate=5 December 2016}}</ref>
| apsis                 = gee

| instruments_list      = {{Infobox spaceflight/Instruments
  | acronym1 = T-SAGE | name1 = Twin-Space Accelerometer for Gravity Experiment
  | acronym2 = DFACS  | name2 = Drag-Free Attitude Control System
  | acronym3 = CGPS   | name3 = Cold Gas Propulsion System
 }}
}}

The '''Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence''' ('''MICROSCOPE''') is a {{convert|300|kg|lb|adj=on}} class [[Biology:Minisatellite|minisatellite]] operated by [[Organization:CNES|CNES]] to test the universality of [[Physics:Free fall|free fall]] (the [[Astronomy:Equivalence principle|equivalence principle]]) with a precision to the order of {{10^|-15}}, 100 times more precise than can be achieved on Earth. It was launched on 25 April 2016 alongside [[Engineering:Sentinel-1B|Sentinel-1B]] and other [[Engineering:Small satellite|small satellite]]s.

==Experiment==
To test the [[Astronomy:Equivalence principle|equivalence principle]] (i.e. the similarity of free fall for two bodies of different composition in an identical gravity field), two differential [[Physics:Accelerometer|accelerometer]]s are used successively. If the equivalence principle is verified, the two sets of masses will be subjected to the same acceleration. If different accelerations have to be applied, the principle will be violated.

The principal experiment is the Twin-Space Accelerometer for Gravity Experiment (T-SAGE), built by [[Organization:ONERA|ONERA]] and composed of two identical accelerometers and their associated, concentric cylindrical masses. One accelerometer serves as a reference and contains two [[Chemistry:Platinum|platinum]]-[[Chemistry:Rhodium|rhodium]] alloy masses, while the other is the test instrument and contains two masses with different [[Physics:Neutron–proton ratio|neutron–proton ratio]]s: one mass of [[Chemistry:Platinum|platinum]]-[[Chemistry:Rhodium|rhodium]] alloy and another mass of [[Chemistry:Titanium|titanium]]-[[Chemistry:Aluminium|aluminium]]-[[Chemistry:Vanadium|vanadium]] alloy (TA6V).  The masses are maintained within their test areas by electrostatic repulsion, designed to render them motionless with respect to the satellite.<ref name="eoportal">{{cite web |url=https://directory.eoportal.org/web/eoportal/satellite-missions/m/microscope |title=MicroSCOPE |work=eoPortal |publisher=[[Organization:European Space Agency|European Space Agency]] |accessdate=7 December 2016}}</ref><ref name="cnes-tsage">{{cite web |url=https://microscope.cnes.fr/en/MICROSCOPE/t-sage.htm |title=T-SAGE Instrument |publisher=CNES |date=1 July 2016 |accessdate=7 December 2016}}</ref>

It is necessary to create a thermally benign environment for the accelerometers. To that end, a [[Astronomy:Sun-synchronous orbit|Sun-synchronous orbit]] provides constant illumination; the experiments are mounted on the end of the satellite bus away from the Sun; and to maintain thermal isolation from the satellite itself, the modes of thermal connection were modelled and wire connections were minimised.<ref name="eoportal" />

==Satellite control==
The satellite employs a [[Astronomy:Attitude control|Drag-Free Attitude Control System]] (DFACS), also called the Acceleration and Attitude Control System (AACS), that uses a double-redundant primary and backup set of four microthrusters (sixteen total) to "fly" the satellite around the test masses. This system takes into account the dynamic forces acting on the spacecraft, including aerodynamic forces due to residual atmosphere, solar pressure forces due to photon impacts, electromagnetic forces within the Earth's magnetosphere, and gravitational forces in the Sun-Earth-Moon system.<ref name="cnes-aacs">{{cite web |url=https://microscope.cnes.fr/en/MICROSCOPE/scaa.htm |title=Attitude and acceleration control |publisher=CNES |date=29 June 2016 |accessdate=7 December 2016}}</ref><ref name="esa20160426">{{cite web |url=http://www.esa.int/Our_Activities/Space_Science/Space_Microscope_to_test_universality_of_freefall |title=Space Microscope to test universality of freefall |publisher=European Space Agency |first=Markus |last=Bauer |date=26 April 2016 |accessdate=7 December 2016}}</ref>

==Launch==
MICROSCOPE was successfully launched on 25 April 2016 at 21:02:13&nbsp;[[UTC]] from the [[Organization:Guiana Space Centre|Guiana Space Centre]] outside Kourou, French Guiana.<ref name="sfnow20160426">{{cite news |url=http://spaceflightnow.com/2016/04/26/soyuz-blasts-off-with-environmental-satellite-general-relativity-probe/ |title=Soyuz blasts off with environmental satellite, general relativity probe |work=Spaceflight Now |first=Stephen |last=Clark |date=26 April 2016 |accessdate=7 December 2016}}</ref> It was carried by a Soyuz-STA booster with a Fregat-M upper stage.<ref name="gunter">{{cite web |url=http://space.skyrocket.de/doc_sdat/microscope.htm |title=MICROSCOPE |work=Gunter's Space Page |first=Gunter |last=Krebs |date=29 April 2016 |accessdate=7 December 2016}}</ref> Other payloads on this flight were the [[Organization:European Space Agency|European Space Agency]]'s [[Engineering:Sentinel-1B|Sentinel-1B]] Earth observation satellite and three [[Engineering:CubeSat|CubeSat]]s: OUFTI-1 from the University of Liège, [[Engineering:E-st@r-II|e-st@r-II]] from the [[Organization:Polytechnic University of Turin|Polytechnic University of Turin]], and AAUSAT-4 from [[Organization:Aalborg University|Aalborg University]].<ref name="sfnow20160426" /><ref name="ariane20160425">{{cite web |url=http://www.arianespace.com/press-release/flight-vs14-a-successful-arianespace-launch-with-soyuz-supporting-sustainable-development-fundamental-physics-and-promoting-space-careers/ |title=Flight VS14 – A successful Arianespace launch with Soyuz, supporting sustainable development, fundamental physics and promoting space careers |publisher=Arianespace |date=25 April 2016 |accessdate=7 December 2016}}</ref>

==Results==
On 4 December 2017, the first results were published. The [[Astronomy:Equivalence principle|equivalence principle]] was measured to hold true within a precision of {{10^|-15}}, improving prior measurements by an order of magnitude.<ref name="Touboul2017">{{cite journal |title=''MICROSCOPE'' Mission: First Results of a Space Test of the Equivalence Principle |journal=Physical Review Letters |first=Pierre |last=Touboul |display-authors=0 |volume=119 |issue=23 |at=231101 |date=8 December 2017 |doi=10.1103/PhysRevLett.119.231101 |pmid=29286705|arxiv=1712.01176 |bibcode=2017PhRvL.119w1101T }}</ref>

==End of Mission==
After completing its mission goals MICROSCOPE was de-commisioned on 18 October 2018. The spacecraft was first passivized and then two 4.5 meter inflatable booms of IDEAS (Innovative DEorbiting Aerobrake System) were deployed to passively de-orbit it through drag enhancement. With this innovative de-orbiting method, MICROSCOPE is expected to reenter the Earth's atmosphere within 25 years instead of 73 years.<ref name="eoportal" /><ref name="EoM_CNES" />

==See also==
* [[Astronomy:Tests of general relativity|Tests of general relativity]]

==References==
{{reflist}}

==External links==
* [https://microscope.cnes.fr/en/ MICROSCOPE website] at CNES.fr

{{European Space Agency}}

[[Category:Artificial satellites orbiting Earth]]

{{Sourceattribution|MICROSCOPE (satellite)|1}}