MICROSCOPE (satellite)

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MICROSCOPE
Mission type Physics
Operator CNES
COSPAR ID 2016-025B
SATCAT no. 41457
Website https://microscope.cnes.fr/en/
Mission duration Planned: 2 years
Elapsed: 2 years, 3 months, 2 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-STA (VS-14)[3]
Launch site Guiana Space Centre ELS[3]
Contractor Arianespace
Entered service 2 May 2016[2]
Orbital parameters
Reference system Geocentric
Regime Low Earth
Semi-major axis 7,090.9 km (4,406.1 mi)
Eccentricity 0.000167
Perigee 711.6 km (442.2 mi)
Apogee 713.9 km (443.6 mi)
Inclination 98.23°
Period 99.03 minutes
Epoch 5 December 2016, 21:17:20 UTC[4]

The Micro-Satellite à traînée Compensée pour l'Observation du Principe d'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 1015, 100 times more precise than can be achieved on Earth. It was launched on 25 April 2016 alongside Sentinel-1B and other small satellites.

Experiment[edit]

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][5]

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[edit]

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.[6][7]

Launch[edit]

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-STA booster with a Fregat-M upper stage.[8] 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[edit]

On 4 December 2017, the first results were published. The equivalence principle was measured to hold true within a precision of 1015, improving prior measurements by an order of magnitude.[9]

See also[edit]

References[edit]

  1. ^ a b c d e f "MicroSCOPE". eoPortal. European Space Agency. Retrieved 7 December 2016. 
  2. ^ a b c d Clark, Stephen (26 April 2016). "Soyuz blasts off with environmental satellite, general relativity probe". Spaceflight Now. Retrieved 7 December 2016. 
  3. ^ a b c "Flight VS14 – A successful Arianespace launch with Soyuz, supporting sustainable development, fundamental physics and promoting space careers". Arianespace. 25 April 2016. Retrieved 7 December 2016. 
  4. ^ "MICROSCOPE - Orbit". Heavens-Above. 5 December 2016. Retrieved 5 December 2016. 
  5. ^ "T-SAGE Instrument". CNES. 1 July 2016. Retrieved 7 December 2016. 
  6. ^ "Attitude and acceleration control". CNES. 29 June 2016. Retrieved 7 December 2016. 
  7. ^ Bauer, Markus (26 April 2016). "Space Microscope to test universality of freefall". European Space Agency. Retrieved 7 December 2016. 
  8. ^ Krebs, Gunter (29 April 2016). "MICROSCOPE". Gunter's Space Page. Retrieved 7 December 2016. 
  9. ^ Touboul, Pierre; et al. (8 December 2017). "MICROSCOPE Mission: First Results of a Space Test of the Equivalence Principle". Physical Review Letters. 119 (23). 231101. arXiv:1712.01176Freely accessible. Bibcode:2017PhRvL.119w1101T. doi:10.1103/PhysRevLett.119.231101. PMID 29286705. 

External links[edit]