Microscope
The Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence carried a mission to test the universality of free fall. This satellite operated by CNES aimed for precision one hundred times better than Earth-based measurements. Scientists sought to verify if two bodies of different composition fall at the same rate in an identical gravity field. The project required engineering that could detect minute differences in acceleration between distinct materials. Researchers designed the craft to function as a floating laboratory in space where external forces were minimized.
Scientists constructed a specialized instrument containing concentric masses made from platinum-rhodium and titanium-aluminium-vanadium alloys. The Twin-Space Accelerometer for Gravity Experiment included two identical accelerometers built by ONERA. One unit served as a reference with platinum-rhodium alloy masses inside its cylindrical housing. The other unit held masses with different neutron, proton ratios including titanium-aluminium-vanadium alloy known as TA6V. Electrostatic repulsion maintained these masses within their test areas while rendering them motionless relative to the satellite body. Engineers mounted the experiment on the end of the satellite bus away from direct sunlight to ensure thermal stability.
A redundant system of microthrusters maintained the spacecraft's position relative to the internal test masses by counteracting external forces. The Drag-Free Attitude Control System utilized sixteen total thrusters arranged in double-redundant primary and backup sets. These microthrusters flew the satellite around the test masses rather than moving the masses themselves. The system accounted for dynamic forces such as aerodynamic drag from residual atmosphere and solar pressure from photon impacts. It also managed electromagnetic forces within Earth's magnetosphere and gravitational influences from the Sun-Earth-Moon system. This precise control allowed the delicate instruments to function without interference from atmospheric turbulence or orbital decay.
The mission began in April 2016 when a Soyuz rocket delivered the payload into a sun-synchronous orbit from French Guiana. Launch occurred at 21:02:13 UTC from the Guiana Space Centre outside Kourou. A Soyuz ST-A booster with a Fregat-M upper stage carried the craft into its designated path. Other payloads on this flight included Sentinel-1B and three CubeSats named OUFTI-1, e-st@r-II, and AAUSAT-4. The satellite entered an orbit that provided constant illumination while keeping experiments mounted away from direct sunlight. This specific trajectory enabled the thermal isolation required for high-precision measurements over time.
Published data confirmed the equivalence principle holds true within an order of magnitude better than previous Earth-based measurements. On the 4th of December 2017 the first results were released showing the principle held true within extreme precision. Researchers measured the similarity of free fall for two bodies of different composition in an identical gravity field. The data improved upon prior measurements by a factor of ten compared to earlier efforts. Scientists concluded that no violation of the equivalence principle existed within the limits of their experimental accuracy. The final report regarding these findings was published in 2022 after years of analysis.
Engineers deployed inflatable booms to increase atmospheric drag and ensure the satellite re-enters Earth's atmosphere within twenty-five years. Decommissioning was announced on the 18th of October 2018 after exhausting its supply of nitrogen fuel. The spacecraft underwent passivation before two IDEAS inflatable booms were deployed to create a higher drag profile. These booms ensured the craft would re-enter Earth's atmosphere much faster than the standard seventy-three year timeline. This strategy prevented long-term orbital debris while allowing the mission to conclude safely. The innovative deorbiting system demonstrated a practical solution for retiring small satellites from low Earth orbit.
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Common questions
What is the Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence designed to test?
The satellite was designed to test the universality of free fall and verify if two bodies of different composition fall at the same rate in an identical gravity field. Scientists sought precision one hundred times better than Earth-based measurements using this floating laboratory.
When did the MICROSCOPE mission begin and from where was it launched?
The mission began in April 2016 when a Soyuz rocket delivered the payload into orbit from French Guiana. Launch occurred at 21:02:13 UTC from the Guiana Space Centre outside Kourou on that date.
Which materials were used for the concentric masses inside the MICROSCOPE Twin-Space Accelerometer for Gravity Experiment?
Scientists constructed specialized instruments containing concentric masses made from platinum-rhodium and titanium-aluminium-vanadium alloys. One unit held platinum-rhodium alloy masses while the other contained titanium-aluminium-vanadium alloy known as TA6V.
On what date were the first results regarding the equivalence principle released by the MICROSCOPE team?
On the 4th of December 2017 the first results were released showing the principle held true within extreme precision. Published data confirmed the equivalence principle holds true within an order of magnitude better than previous Earth-based measurements.
Why did engineers deploy inflatable booms to the MICROSCOPE satellite before decommissioning?
Engineers deployed inflatable booms to increase atmospheric drag and ensure the satellite re-enters Earth's atmosphere within twenty-five years. Decommissioning was announced on the 18th of October 2018 after exhausting its supply of nitrogen fuel.