MICROSCOPE

Mission type| Physics
Operator| CNES
COSPAR ID| 2016-025B
SATCAT no.| 41457
Website| https://microscope.cnes.fr/en/
Mission duration| Planned: 2 years
Final: 2 years, 5 months, 22 days
Spacecraft properties
Bus| Myriade[1]
Manufacturer| CNES * Airbus
Launch mass| 330 kg (728 lb)[1]
Dimensions| 138 × 104 × 158 cm (54 × 41 × 62 in)[1]
Power| 140 watts[1]
Start of mission
Launch date| 25 April 2016, 21:02:13 (2016-04-25UTC21:02:13) UTC[2]
Rocket| Soyuz ST-A (VS-14)[3]
Launch site| Guiana Space Centre ELS[3]
Contractor| Arianespace
Entered service| 2 May 2016[2]
End of mission
Disposal| Decommissioned
Deactivated| c. 18 October 2018 (2018-10-19)[4]
Orbital parameters
Reference system| Geocentric
Regime| Low Earth
Semi-major axis| 7,090.9 km (4,406.1 mi)
Eccentricity| 0.000167
Perigee altitude| 711.6 km (442.2 mi)
Apogee altitude| 713.9 km (443.6 mi)
Inclination| 98.23°
Period| 99.03 minutes
Epoch| 5 December 2016, 21:17:20 UTC[5]
| Instruments

T-SAGE| Twin-Space Accelerometer for Gravity Experiment
DFACS| Drag-Free Attitude Control System
CGPS| Cold Gas Propulsion System

The Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence (Micro-Satellite with Compensated Drag for Observing the Principle of Equivalence, MICROSCOPE) is a 300-kilogram (660 lb) class minisatellite operated by CNES to test the universality of free fall (the equivalence principle) with a precision to the order of 10−15,[6] 100 times more precise than can be achieved on Earth. It was launched on 25 April 2016 alongside Sentinel-1B and other small satellites, and was decommissioned around 18 October 2018 after completion of its science objectives.[4] The final report was published in 2022.[7]

## Contents

* 1 Experiment
* 2 Satellite control
* 3 Launch
* 4 Results
* 5 End of mission
* 6 See also
* 7 References
* 8 External links

## Experiment

To test the equivalence principle (i.e. the similarity of free fall for two bodies of different composition in an identical gravity field), two differential accelerometers 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 ONERA and composed of two identical accelerometers and their associated, concentric cylindrical masses. One accelerometer serves as a reference and contains two platinum-rhodium alloy masses, while the other is the test instrument and contains two masses with different neutron–proton ratios: one mass of platinum-rhodium alloy and another mass of titanium-aluminium-vanadium alloy (TA6V). The masses are maintained within their test areas by electrostatic repulsion, designed to render them motionless with respect to the satellite.[1][8]

It is necessary to create a thermally benign environment for the accelerometers. To that end, a 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.[1]

## Satellite control

The satellite employs a 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.[9][10]

## Launch

MICROSCOPE was successfully launched on 25 April 2016 at 21:02:13 UTC from the Guiana Space Centre outside Kourou, French Guiana.[2] It was carried by a Soyuz ST-A booster with a Fregat-M upper stage.[11] Other payloads on this flight were the European Space Agency's Sentinel-1B Earth observation satellite and three CubeSats: OUFTI-1 from the University of Liège, e-st@r-II from the Polytechnic University of Turin, and AAUSAT-4 from Aalborg University.[2][3]

## Results

On 4 December 2017, the first results were published. The equivalence principle was measured to hold true within a precision of 10−15, improving prior measurements by an order of magnitude.[12]

## End of mission

After completing its mission goals and exhausting its supply of nitrogen fuel, the decommissioning of MICROSCOPE was announced on 18 October 2018. The spacecraft was first passivated, then two 4.5-metre (15 ft) IDEAS (Innovative DEorbiting Aerobrake System) inflatable booms were deployed to passively de-orbit the spacecraft by creating a higher drag profile. By these means MICROSCOPE is expected to re-enter Earth's atmosphere within 25 instead of 73 years.[1][4]

## See also

* Tests of general relativity
* Timeline of gravitational physics and relativity

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 "MicroSCOPE". eoPortal. European Space Agency. https://directory.eoportal.org/web/eoportal/satellite-missions/m/microscope.
2. ↑ 2.0 2.1 2.2 2.3 Clark, Stephen (26 April 2016). "Soyuz blasts off with environmental satellite, general relativity probe". Spaceflight Now. http://spaceflightnow.com/2016/04/26/soyuz-blasts-off-with-environmental-satellite-general-relativity-probe/.
3. ↑ 3.0 3.1 3.2 "Flight VS14 – A successful Arianespace launch with Soyuz, supporting sustainable development, fundamental physics and promoting space careers". Arianespace. 25 April 2016. http://www.arianespace.com/press-release/flight-vs14-a-successful-arianespace-launch-with-soyuz-supporting-sustainable-development-fundamental-physics-and-promoting-space-careers/.
4. ↑ 4.0 4.1 4.2 Bresson, Pascale; Sart, Raphaël (18 October 2018). "End of mission for Microscope - CNES's satellite bows out with successful and innovative de-orbiting" (Press release). CNES. Retrieved 25 March 2019.
5. ↑ "MICROSCOPE - Orbit". Heavens-Above. 5 December 2016. http://heavens-above.com/orbit.aspx?satid=41457.
6. ↑ Brax, Philippe (September 14, 2022). "Satellite Confirms the Principle of Falling". Physics (American Physical Society (APS)) 15 (94): 94. doi:10.1103/Physics.15.94. Bibcode: 2022PhyOJ..15...94B. https://physics.aps.org/articles/v15/94.
7. ↑ Touboul, Pierre; Métris, Gilles; Rodrigues, Manuel; Bergé, Joel; Robert, Alain et al. (2022). "MICROSCOPE Mission: Final Results of the Test of the Equivalence Principle.". Physical Review Letters 129 (12). doi:10.1103/PhysRevLett.129.121102. PMID 36179190. Bibcode: 2022PhRvL.129l1102T. https://hal.science/hal-03781337v1/file/tou1pl.pdf.
8. ↑ "T-SAGE Instrument". CNES. 1 July 2016. https://microscope.cnes.fr/en/MICROSCOPE/t-sage.htm.
9. ↑ "Attitude and acceleration control". CNES. 29 June 2016. https://microscope.cnes.fr/en/MICROSCOPE/scaa.htm.
10. ↑ Bauer, Markus (26 April 2016). "Space Microscope to test universality of freefall". European Space Agency. http://www.esa.int/Our_Activities/Space_Science/Space_Microscope_to_test_universality_of_freefall.
11. ↑ Krebs, Gunter (29 April 2016). "MICROSCOPE". Gunter's Space Page. http://space.skyrocket.de/doc_sdat/microscope.htm.
12. ↑ Touboul, Pierre (8 December 2017). "MICROSCOPE Mission: First Results of a Space Test of the Equivalence Principle". Physical Review Letters 119 (23): 231101. doi:10.1103/PhysRevLett.119.231101. PMID 29286705. Bibcode: 2017PhRvL.119w1101T.

## External links

* MICROSCOPE website at CNES.fr

* v
* t
* e

European Space Agency

| Spaceports|

* Guiana Space Centre
* Esrange

|

Launch vehicles|

* Ariane 5
* Ariane 6
* Arianespace Soyuz
* Vega

Facilities|

* Space Operations Centre
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Communications|

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Predecessors|

* European Launcher Development Organisation
* European Space Research Organisation

Related topics|

* Arianespace
* ESA Television
* EUMETSAT
* European Space Camp
* GEWEX
* Planetary Science Archive

Projects and missions

Science|

| Solar physics|

* ISEE-2 (1977–87)
* Ulysses (1990–2009)
* SOHO (1995–present)
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* Solar Orbiter (2020)
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Planetary science|

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Astronomy and
cosmology

* Cos-B (1975–82)
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Earth observation|

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ISS spaceflight|

* ISS contribution (1998–present)
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Telecommunications|

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Cancelled and proposed|

* ALTIUS
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Failed|

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Future missions in italics

* Category
* Commons
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Orbital launches in 2016

January|

Belintersat-1 – Jason-3 – IRNSS-1E – Intelsat 29e – Eutelsat 9B

February|

BeiDou M3-S – USA-266 / GPS IIF-12 – Kosmos 2514 / GLONASS-M 751 – Kwangmyŏngsŏng-4 – USA-267 / NROL-45 / Topaz-4 – Sentinel-3A – ASTRO-H / Hitomi * ChubuSat-2 * ChubuSat-3 * Horyu-4

March|

SES-9 – Eutelsat 65 West A – IRNSS-1F – Resurs-P No.3 – ExoMars Trace Gas Orbiter * Schiaparelli EDM – Soyuz TMA-20M – Cygnus CRS OA-6 (Diwata-1 * Flock-2e' × 20  * Lemur-2 × 9) – Kosmos 2515 / Bars-M No.2 – BeiDou IGSO-6 – Progress MS-02

April|

Shijian-10 – Dragon CRS-8 * BEAM – Sentinel-1B * MICROSCOPE * AAUSAT-4 * e-st@r-II * OUFTI-1 – Mikhailo Lomonosov * Aist-2D * SamSat 218 – IRNSS-1G

May|

JCSAT-14 – Yaogan 30 – Galileo FOC-10, FOC-11 – Thaicom 8 – Kosmos 2516 / GLONASS-M 753 – Ziyuan III-02 * ÑuSat 1, 2

June|

Kosmos 2517 / Geo-IK-2 No.12 – Intelsat 31 / DLA-2 – USA-268 / NROL-37 – BeiDou G7 – Eutelsat 117 West B * ABS-2A – Echostar 18 * BRIsat – CartoSat-2C * BIROS * GHGsat * LAPAN-A3 * M3MSat * SkySat-C1 * Flock-2p × 12 * SathyabamaSat * Swayam – MUOS-5 – Chinese next-generation crew capsule scale model * Aolong-1 * Aoxiang Zhixing * Tiange-1 * Tiange-2 – Shijian 16-02

July|

Soyuz MS-01 – Progress MS-03 – Dragon CRS-9 – USA-269 / NROL-61

August|

Tiantong-1 01 – Gaofen-3 – JCSAT-16 – QUESS / Mozi / Micius * ³Cat-2 * LiXing-1 – USA-270 / GSSAP #3 * USA-271 / GSSAP #4 – Intelsat 33e * Intelsat 36 – Gaofen-10

September|

Amos-6 – INSAT-3DR – OSIRIS-REx – Ofek-11 – Tiangong-2 – PeruSat-1 * SkySat × 4 – ScatSat-1 * Alsat-1B * Alsat-2B * Blacksky Pathfinder-1 * Alsat-1N * CanX-7 * PISat * Pratham

October|

Sky Muster II * GSAT-18 – Shenzhou 11 – Cygnus CRS OA-5 (Lemur-2 × 4) – Soyuz MS-02

November|

Himawari 9 – Shijian-17 – XPNAV 1 – WorldView-4 * CELTEE 1 * Prometheus-2 × 2 * AeroCube 8 × 2 * U2U * RAVAN – Yunhai-1 – Galileo FOC 7, 12, 13, 14 – Soyuz MS-03 – GOES-R – Tianlian I-04

December|

Progress MS-04 – Göktürk-1 – Resourcesat-2A – WGS-8 – HTV-6 / Kounotori 6 * (EGG * TuPOD * UBAKUSAT * AOBA-VELOX * STARS * FREEDOM * ITF * Waseda-SAT * OSNSAT * Tancredo-1 * TechEDSat * Lemur-2 × 4) – Fengyun 4A – CYGNSS × 8 – EchoStar 19 – Arase / ERG – TanSat * Spark × 2 – Star One D1 * JCSAT-15 – SuperView / Gaojing-1 01, 02 * Bayi Kepu 1

Launches are separated by dashes ( – ), payloads by dots ( * ), multiple names for the same satellite by slashes ( / ). Cubesats are smaller.
Crewed flights are bolded. Launch failures are in italics. Payloads deployed from other spacecraft are (enclosed in brackets).

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