MICROSCOPE mission analysis, requirements and expected performance

The MICROSCOPE mission aimed to test the Weak Equivalence Principle (WEP) to a precision of $10^{-15}$. The WEP states that two bodies fall at the same rate on a gravitational field independently of their mass or composition. In MICROSCOPE, two masses of different compositions (titanium and platinum alloys) are placed on a quasi-circular trajectory around the Earth. They are the test-masses of a double accelerometer. The measurement of their accelerations is used to extract a potential WEP violation that would occur at a frequency defined by the motion and attitude of the satellite around the Earth. This paper details the major drivers of the mission leading to the specification of the major subsystems (satellite, ground segment, instrument, orbit...). Building upon the measurement equation, we derive the objective of the test in statistical and systematic error allocation and provide the mission's expected error budget.Comment: References update

MICROSCOPE mission: first results of a space test of the equivalence principle

According to the weak equivalence principle, all bodies should fall at the same rate in a gravitational field. The MICROSCOPE satellite, launched in April 2016, aims to test its validity at the 10−15 precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. A nonvanishing result would correspond to a violation of the equivalence principle, or to the discovery of a new long-range force. Analysis of the first data gives δ(Ti,Pt)=[−1±9(stat)±9(syst)]×10−15 (1σ statistical uncertainty) for the titanium-platinum Eötvös parameter characterizing the relative difference in their free-fall accelerations

Microscope: A Microsatellite for Equivalence Principle Measurement in Space

The MICROSCOPE mission is developed in the frame of the CNES Myriade micro satellite family. The project is currently ending its Phase B, the Preliminary Design Review has been held in March 2011 and the launch is planned in 2015. The scientific objective of the mission consists in a test of the Equivalence Principle (EP) between gravitational mass and inertial mass with a relative accuracy of 10-15; the payload is composed of a set of two 6-axis differential accelerometers developed by ONERA. To achieve this goal, a drag free control of the satellite has to be achieved in order to limit the non-gravitational accelerations on the payload below 3.10-10 ms-2*Hz-1/2. This paper begins with a introduction of the mission and the payload, explaining how mission requirements and payload I/F strongly constrain the design of spacecraft (drag free, microperturbation and stability). The functional chains of the satellite are presented in detail with an emphasis on mechanical and thermal architecture, Acceleration and Attitude Control System (AACS) and Cold Gas Propulsion System (CGPS). It is shown how the design of the satellite is optimized, melting new advanced technology (Payload, AACS, CGPS) and low cost, well proven methods and equipment of Myriade family

Microscope: A Scientific Microsatellite Development

MICROSCOPE is a CNES-ESA-ONERA-CNRS-OCA-DLT-ZARM scientific mission developed in the frame of Myriade Microsatellite family. The scientific objective consists to test the Equivalence Principle between gravitational mass and inertial mass with an relative accuracy of 10-15 ; i.e. one hundred times better than the one obtained today on Earth. Satellite has been launched the 25th of April 2016 for a 2 years in orbit lifetime. This paper begins with a introduction of the scientific goals, a presentation of the mission and the payload definition, explaining how the S/C has evolved in time in order to fulfil the stringent mission requirement always keeping in line with microsatellite development approach. The main part of the paper is focused on the description of actual spacecraft design with a presentation of all the functional chains, their performances and the ground validation process. Most innovative elements are the AACS (Attitude and Acceleration Control System) running simultaneously 38 control loops in order to keep the payload in drag-free condition during scientific sessions and (CGPS) Cold Gas Propulsion System generating and modulating a continuous thrust in the range from 1 to 300 μN with an accuracy of 0.1 μN. A special attention is given to micro perturbation control plan and satellite validation logic due to high sensitivity of PL and the impossibility to perform full representative test on ground. It is shown how the design of the satellite is optimized, melting new advanced technology and low cost, well proven methods coming from Myriade family. The paper will end with a presentation of first in-flight results especially the commissioning phase

MICROSCOPE Satellite and its Drag-Free and Attitude Control System

This paper focus on the description of the design and performance of the MICROSCOPE satellite and its Drag-Free and Attitude Control System (DFACS). The satellite is derived from CNES' Myriade platform family, albeit with significant upgrades dictated by the unprecedented MICROSCOPE's mission requirements. The 300kg drag-free microsatellite has completed its 2-year flight with higher-than-expected performances. Its passive thermal concept allowed for variations smaller than 1 $\mu$K at the measurement frequency $f_{\rm{EP}}$. The propulsion system provided a 6 axis continuous and very low noise thrust from zero to some hundreds of micronewtons. Finally, the performance of its DFACS (aimed at compensating the disturbing forces and torques applied to the satellite) is the finest ever achieved in low Earth orbit, with residual accelerations along the three axes are lower than $10^{-12} {\rm m/s}^2$ at $f_{\rm{EP}}$ over 8 days

MICROSCOPE satellite and its drag-free and attitude control system

International audienceThis paper focuses on the description of the design and performance of the MICROSCOPE satellite and its drag-free and attitude control system. The satellite is derived from CNES’ Myriade platform family, albeit with significant upgrades dictated by the unprecedented MICROSCOPE’s mission requirements. The 300 kg drag-free microsatellite has completed its 2 years flight with higher-than-expected performances. Its passive thermal concept allowed for temperature variations smaller than 1 μK at the frequency of the equivalence principle test f$_{EP}$. The propulsion system provided a six-axis continuous and very low noise thrust from zero to some hundreds of micronewtons. Finally, the performance of its DFACS (aimed at compensating the disturbing forces and torques applied to the satellite) is the finest ever achieved in low Earth orbit, with residual accelerations along the three axes lower than 10$^{−12}$ m s$^{−2}$ at f$_{EP}$ over 8 days

MICROSCOPE. mission analysis, requirements and expected performance

International audienceThe MICROSCOPE mission aimed to test the weak equivalence principle (WEP) to a precision of 10$^{−15}$. The WEP states that two bodies fall at the same rate on a gravitational field independently of their mass or composition. In MICROSCOPE, two masses of different compositions (titanium and platinum alloys) are placed on a quasi-circular trajectory around the Earth. They are the test-masses of a double accelerometer. The measurement of their accelerations is used to extract a potential WEP violation that would occur at a frequency defined by the motion and attitude of the satellite around the Earth. This paper details the major drivers of the mission leading to the specification of the major subsystems (satellite, ground segment, instrument, orbit…). Building upon the measurement equation, we derive the objective of the test in statistical and systematic error allocation and provide the mission’s expected error budget

MICROSCOPE: systematic errors

International audienceThe MICROSCOPE mission aims to test the weak equivalence principle (WEP) in orbit with an unprecedented precision of 10$^{−15}$ on the Eötvös parameter thanks to electrostatic accelerometers on board a drag-free micro-satellite. The precision of the test is determined by statistical errors, due to the environment and instrument noises, and by systematic errors to which this paper is devoted. Systematic error sources can be divided into three categories: external perturbations, such as the residual atmospheric drag or the gravity gradient at the satellite altitude, perturbations linked to the satellite design, such as thermal or magnetic perturbations, and perturbations from the instrument internal sources. Each systematic error is evaluated or bounded in order to set a reliable upper bound on the WEP parameter estimation uncertainty

MICROSCOPE: systematic errors

The MICROSCOPE mission aims to test the Weak Equivalence Principle (WEP) in orbit with an unprecedented precision of 10$^{-15}$ on the Eötvös parameter thanks to electrostatic accelerometers on board a drag-free micro-satellite. The precision of the test is determined by statistical errors, due to the environment and instrument noises, and by systematic errors to which this paper is devoted. Systematic error sources can be divided into three categories: external perturbations, such as the residual atmospheric drag or the gravity gradient at the satellite altitude, perturbations linked to the satellite design, such as thermal or magnetic perturbations, and perturbations from the instrument internal sources. Each systematic error is evaluated or bounded in order to set a reliable upper bound on the WEP parameter estimation uncertainty

The High Time Resolution Spectrometer (HTRS) aboard the International X-ray Observatory (IXO)

The High Time Resolution Spectrometer (HTRS) is one of the five focal plane instruments of the International X-ray Observatory (IXO). The HTRS is the only instrument matching the top level mission requirement of handling a one Crab X-ray source with an efficiency greater than 10%. It will provide IXO with the capability of observing the brightest X-ray sources of the sky, with sub-millisecond time resolution, low deadtime, low pile-up (less than 2% at 1 Crab), and CCD type energy resolution (goal of 150 eV FWHM at 6 keV). The HTRS is a non-imaging instrument, based on a monolithic array of Silicon Drift Detectors (SDDs) with 31 cells in a circular envelope and a X-ray sensitive volume of 4.5 cm2 x 450 μm. As part of the assessment study carried out by ESA on IXO, the HTRS is currently undergoing a phase A study, led by CNES and CESR. In this paper, we present the current mechanical, thermal and electrical design of the HTRS, and describe the expected performance assessed through Monte Carlo simulations