MICROSCOPE – fabricating test masses for an in‐orbit test of the equivalence principle

Hagedorn, D.; Heyne, H.-P.; Metschke, Stephan; Langner, Uwe; Grüner, Sven; Löffler, F.; Lebat, Vincent; Rodrigues, Manuel; Touboul, Pierre

doi:10.1002/andp.201300074

Cited by 4 publications

(4 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The cylindrical test-masses are what differentiates the sensor units. They have been produced and precisely characterised in the Physikalisch-Technische Bundesanstalt (PTB) laboratory, in Braunschweig, the German National Metrology Institute, with a metrology accuracy better than 1 µm [54]. The SU PtRh10 platinum-rhodium alloy contains 90% by mass of Pt ( A = 195.1, Z = 78) and 10% Rh ( A = 102.9, Z = 45).…”

Section: Test-massesmentioning

confidence: 99%

Space test of the equivalence principle: first results of the MICROSCOPE mission

Touboul

Métris

Rodrigues

et al. 2019

Class. Quantum Grav.

Self Cite

135

View full text Add to dashboard Cite

The weak equivalence principle (WEP), stating that two bodies of different compositions and/or mass fall at the same rate in a gravitational field (universality of free fall), is at the very foundation of general relativity. The MICROSCOPE mission aims to test its validity to a precision of 10−15, two orders of magnitude better than current on-ground tests, by using two masses of different compositions (titanium and platinum alloys) on a quasi-circular trajectory around the Earth. This is realised by measuring the accelerations inferred from the forces required to maintain the two masses exactly in the same orbit. Any significant difference between the measured accelerations, occurring at a defined frequency, would correspond to the detection of a violation of the WEP, or to the discovery of a tiny new type of force added to gravity. MICROSCOPE’s first results show no hint for such a difference, expressed in terms of Eötvös parameter (both 1 uncertainties) for a titanium and platinum pair of materials. This result was obtained on a session with 120 orbital revolutions representing 7% of the current available data acquired during the whole mission. The quadratic combination of 1 uncertainties leads to a current limit on of about .

show abstract

Section: Test-massesmentioning

confidence: 99%

Space test of the equivalence principle: first results of the MICROSCOPE mission

Touboul

Métris

Rodrigues

et al. 2019

Class. Quantum Grav.

Self Cite

135

View full text Add to dashboard Cite

show abstract

“…With data available on the masses and the geometry of the test cylinders [11,28,29] we get for this ratio (in modulus) about 3.3. Thus, non-gravitational perturbations whose accelerations are proportional to the area-to-mass ratio of the test cylinders, give rise to differential accelerations 3.3 times larger in SUEP than in SUREF, simply because of the way they have been designed, all other physical parameters being the same.…”

Section: Thermal Noise Systematic Errors and The "Zero-check" Smentioning

confidence: 88%

Testing the equivalence principle in space after the MICROSCOPE mission

Nobili

Anselmi

2018

Phys. Rev. D

View full text Add to dashboard Cite

Tests of the Weak Equivalence Principle (WEP) can reveal a new, composition dependent, force of nature or disprove many models of new physics. For the first time such a test is being successfully carried out in space by the MICROSCOPE satellite. Early results show no violation of the WEP sourced by the Earth for Pt and Ti test masses with random errors (after 8.26 d of integration time) of about 1 part in 10 14 , and systematic errors of the same magnitude. This result improves by about 10 times over the best ground tests with rotating torsion balances despite 70 times less sensitivity to differential accelerations, thanks to the much stronger driving signal in orbit. The measurement is limited by thermal noise from internal damping in the gold wires used for electrical grounding, related to their fabrication and clamping. This noise was shown to decrease when the spacecraft was set to rotate faster than planned. The result will improve by the end of the mission, as thermal noise decreases with more data. Not so systematic errors. We investigate major nongravitational effects and find that MICROSCOPE's "zero-check" sensor, with test masses both made of Pt, does not allow their separation from the signal. The early test reports an upper limit of systematic errors in the Pt-Ti sensor which are not detected in the Pt-Pt one, hence would not be distinguished from a violation. Once all the integration time available is used to reduce random noise there will be no time left to check systematics. MICROSCOPE demonstrates the huge potential of space for WEP tests of very high precision and indicates how to reach it. To realize the potential, a new experiment needs the spacecraft to be in rapid, stable rotation around the symmetry axis (by conservation of angular momentum), needs high quality state-of-the-art mechanical suspensions as in the most precise gravitational experiments on ground, and must allow multiple checks to discriminate a violation signal from systematic errors. The design of the "Galileo Galilei" (GG) experiment, aiming to test the WEP to 1 part in 10 17 unites all the needed features, indicating that a quantum leap in space is possible provided the new experiment heeds the lessons of MICROSCOPE.

show abstract

“…Test-mass metrology. The cylindrical test-masses have been finely produced and characterised in the laboratory of Physikalisch-Technische-Bundesanstalt (PTB), in Brunswick, with accuracy better than 2 μm [19]. The masses have been measured with a maximum error of 0.025 mg.…”

Section: On-ground Instrument Tests and Performancementioning

confidence: 99%

MICROSCOPE instrument description and validation

Rodrigues

Liorzou

Touboul

et al. 2022

Class. Quantum Grav.

Self Cite

View full text Add to dashboard Cite

This paper focuses on the dedicated accelerometers developed for the MICROSCOPE mission taking into account the specific range of acceleration to be measured on board the satellite. Considering one micro-g and even less as the full range of the instrument with an objective of one femto-g resolution, that leads to a customized concept and a high-performance electronics for the sensing and servo-actuations of the accelerometer test-masses. This range and performance directed the payload development plan. In addition to a very accurate geometrical sensor core, a high performance electronics architecture provides the measurement of the weak electrostatic forces and torques applied to the test-masses. A set of capacitive detectors delivers the position and the attitude of the test-mass with respect to a very steady gold-coated cage made in silica. The voltages applied on the electrodes surrounding each test-mass are finely controlled to generate the adequate electrical field and so the electrostatic pressures on the test-mass. This field maintains the test-mass motionless with respect to the instrument structure. Digital control laws are implemented in order to enable instrument operation flexibility and a weak position detector noise. These electronics provide both the scientific data for MICROSCOPE’s test of the weak equivalence principle and the input for the satellite drag-free and attitude control system.

show abstract

MICROSCOPE – fabricating test masses for an in‐orbit test of the equivalence principle

Cited by 4 publications

References 5 publications

Space test of the equivalence principle: first results of the MICROSCOPE mission

Space test of the equivalence principle: first results of the MICROSCOPE mission

Testing the equivalence principle in space after the MICROSCOPE mission

MICROSCOPE instrument description and validation

Contact Info

Product

Resources

About