MICROSCOPE mission overview - OCA

1 Pierre Touboul, Mission Overview, MICROSCOPE Colloquium II, Palaiseau, 29-30 Jan. 2013

MICROSCOPE mission overview

Pierre Touboul , on behalf of the MICROSCOPE team

ONERA, The French Aerospace Lab, BP 80100, F- 91123 Palaiseau

[email protected]

Cnes Courtesy


UFF TEST RATIONALE

• UFF violation one of the invariance of the EEP (UFF, LPI, LLI) violated!

• MICROSCOPE Objective : 10-15 accuracy

• See T. Damour, P. Fayet, E. Fishbach, E. Adelberger, C. Lämmerzahl, L. Blanchet, S. Reynaud, Ph. Brax, B. Julia...

• Physics is not completely understood new Physics New experiments New type of results

• MICROSCOPE is the first accurate UFF test in space

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Test of Universality of Free Fall : from initial experiments...

Galilée (1590)

•Initial conditions ?•Gravity gradients ?•Environment effects ?•Relative position measurement ?

•Initial conditions ?•Gravity gradients ?•Environment effects ?

No atmospheric drag•Relative position measurement ?

hammer and feather

Apollo 15 (1971)

David Scott, A. Worden, J. Irwin


Torsion Balance Experiments: A Low-energy Frontier of Particle Physics, E. G. Adelberger et al., Prog. Part. Nucl. Phys 62, 102 (2009)

aN(Be) − aN(Ti) = ( +0.6 ± 3.1) × 10−15 m/s2

aW(Be) − aW(Ti) = (−2.5 ± 3.5) × 10−15 m/s2

η (Be,Ti) = ( +0.3 ± 1.8) × 10−13 in 75 days of dataaN(Be) − aN(Al) = (−2.6 ± 2.5) × 10−15 m/s2

aW(Be) − aW(Al) = ( +0.7 ± 2.5) × 10−15 m/s2

η (Be,Al) = (−1.5 ± 1.5) × 10−13 in 96 days of data

Fixed relative motion of the test masses & Measurement of the Torques

Laboratory tests : Eötwash group

Test of Universality of Free Fall : to present tests...see presentations by Eric Adelberger and François Mignard

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Lunar laser ranging• laser impulse 100ps & 1 photon detected back, for every 1020 emitted at every 100 pulses• relative motion of Earth and Moon in orbit around the Sun

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J. G. Williams, X. X. Newhall, and J. O. Dickey, Phys.Rev. D 53, 6730 (1996).

Earth gravity @ 700km ~ 8 ms-2

Sun gravity @ Earh ~ 1000 less


Permanent pico-meter control of the 2 masses No fluctuations of the mass environment due to relative motion Centring initial and permanent conditions : 20 µm known at 0.1 µm in orbital plane (X,Z) Measurement = Necessary forces to control the same orbital motion Satellite impose the common motion : reduced instrument better operation

Galileo Galilei « Free fall » in space Microscope

TEST OF UNIVERSALITY OF FREE FALL and MICROSCOPE space experiment...

•Measurement = relative motion of the two masses in geodetic motion• satellite as a shield to the mass --> drag free null or weak stiffness between masses and satellite displacement of the satellite & instrument apparatus wrt masses fluctuations of the mass motion environment

2 test masses made of different composition Gravitational Source : the Earth Kinematic Acceleration : Orbital motion Identical initial conditions of motion


2 accurate test masses Dedicated space instrument = differential accelerometer One Differential accelerometer comprises 2 inertial electrostatic sensors 2 pairs of masses Pt-Pt & Pt-Ti 2 diff. accelero. double difference

Satellite with drag compensation & fine attitude control Fine passive thermal control and soft EM environment

Mission duration : 18 months – 2 years Heliosynchronous orbit, 700 km altitude; e < 5 10-3

MICROSCOPE space experiment

Pt

Ti

B/ Z/ (N-Z)/

1.008911 0.46309 0.082731.008009 0.40296 0.20208

Mass material : Pt and Ti alloys Nuclear properties

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Material 1 (Pt)

Material 2 (Ti)

gravity field

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• centering• shape : spherical inertia, multipoles• material density homogeneity

• Angular acceleration & centrifugal acceleration : to be controlled• Coriolis stability of velocities • Cinematic relative acceleration stability of the configuration and control


Different experiment conditions : Modulation of the gravity field in instrument frameInertial pointing with 2 directions : to the Earth @ node or normal fEP = forb = 1.68 10-4 HzRotating pointing with 2 frequencies : 73/20 forb & 97/20 forb fEP = forb+ fspin= 7.8 10-4 Hz & 9.8 10-4 Hz

Data Processing and Validation of the levels of the disturbing sourcesTest duration : series of 20 orbits 1.2 105 sSampling period : 0.25 s Signal to be observed at EP test phase & frequency rejection of stochastic and tone disturbing signals

Very accurate instrument calibration sensitivity matching / alignments / quadratic sensitivity corrections of the measurements

MICROSCOPE space experiment

EP test Axis

Material 1 (Pt)

Material 2 (Ti)

gravity field


The Measure

What do we measure ? Earth’s, satellite, instrument, physics contributions

see for details presentations by Gilles Métris, Agnès Levy, Emilie Hardy

Stochastic and Tone Signals to be considered with a limited observation period and some lacks of data Detailed Specifications for S/C Sub-Systems, Instrument Environment & Instrument Performances Accurate in orbit calibration A posteriori estimation and corrections

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Measured Acceleration Difference

Bias differencelimited thermal

fluctuations

Common Mode Sensitivity Matrix (Inst. Scale Factor & Attitude,

Coupling)Estimated by calibration

or limited by construction

Earth Gravity gradient tensor

Computed with Model, S/C position & attitude

and Removed

Inertia Tensor (Angular Velocity and Acceleration)

Minimized by AOCSfrom SST & Inst. data

Differential Mode Sensitivity Matrix (Scale Factor

Mismatching & Misalignment)Estimated by calibration

Common mode acceleration

(S/C drag-free Control from Sensor common

data)

Instrumentnoises

&couplings

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Space Electrostatic accelerometersfor Earth gravity field recovery

CHAMP (CNES-DLR), July 2000- 2009 GRACE (NASA-JPL), March 2002 – 2015 ?

GOCE (ESA), March 2009 – May 2013 ?

• Γn: 3·10-9 ms-2 /Hz1/2

• Γmax: 10-4 ms-2

• [0.2·10-3; 10-1 ] Hz

• Γn: 3·10-9 ms-2 /Hz1/2

• Γmax: 10-4 ms-2

• [0.2·10-3; 10-1 ] Hz

• Γn: 1.0·10-10 ms-2 /Hz1/2

• Γmax: 510-5 ms-2

• [0.1·10-3; 10-1 ] Hz

• Γn: 1.0·10-10 ms-2 /Hz1/2

• Γmax: 510-5 ms-2

• [0.1·10-3; 10-1 ] Hz

• Γn: 2.0·10-12 ms-2 /Hz1/2

• Γmax: 610-6 ms-2

• [5·10-3; 10-1 ] Hz

• Γn: 2.0·10-12 ms-2 /Hz1/2

• Γmax: 610-6 ms-2

• [5·10-3; 10-1 ] Hz

altitude~500kmaltitude~500km

altitude~260km

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In line common acceleration external acceleration at CoG

In line differential acceleration Gravity Gradient measurement

transverse differential acceleration angular acceleration

GOCE Seminar, 10-11 Jan 2013, Onera :Analysis of the obtained performance

Today : 3971 days in orbit


GOCE performance, Accelerometer performanceSee details presentation by Bruno Christophe

Measured Trace : ~ 24 mE/Hz1/2

Depends on : Accelerometer performance Calibration performance Attitude control performance Linearity

VXX, VYY, VZZ

Accelerometer PSD in 40-100 mHz

ASH3,6 : 6.7 10-12 m/s2/Hz1/2

ASH1,4 : 3.9 10-12 m/s2/Hz1/2

ASH2,5 : 3.1 10-12 m/s2/Hz1/2

Assuming : accelerometers, the only source of the EGG noise

MICROSCOPE Expected Performancesincluding environment stochastic variations:• inertial pointing : 3.74 - 4.9 10-12 ms-2Hz1/2 @ forb=fep

• rotating pointing : 1.55 – 2.03 10-12 ms-2Hz1/2 @ fep

GOCE MICROSCOPE Gold wire : Ø= 5 m Ø=7.5 m PT-Rh Proof mass : m= 320g m=400 - 307 g Gap Y,Z : e = 299 m e= 600 m PM Polarisation : Vp = 7.5 V Vp =5 V Detection : Vd = 7.6 V @ 100 KHz Vd = 7.07 V @ 100 KHz Detector gain 1.7 mV / nano-m 0.3 - 0.26 mV / nano-m Scale factor :

Science data 1. 10-7ms-2/V 1.8 - 2.1 10-7 ms-2/V DFACS data 17. 10-6 ms-2/V 0.7- 1.7 10-6 ms-2/V

Range ± 6.5 10-6 ms-2 ± 4.8 - 4.6 10-7 ms-2

Expected Res. < 2 10-12 ms-2 Hz-1/2 < 2 10-12 ms-2 Hz-1/2

J Geod (2011) 85:759–775DOI 10.1007/s00190-011-0497-4


GOCE experience returnsee for details presentation by B. Christophe and B. Foulon

• Drag compensation • Attitude control• Alignments & scale factor matching• Non linearities

R. Rummel et al. J Geod (2011) 85:777–790

Björn Frommknecht et al. J Geod (2011) 85:759–775

Björn Frommknecht et al. J Geod (2011) 85:759–775

R. Floberghagen et al. J Geod (2011) 85:749–758


MICROSCOPE : A dedicated instrument

One differential accelerometer = 2 inertial sensors Each inertial sensors exploits electrostatic Concept & Technology similar to GOCE•6 servo-channels and associated electrode sets sensing and actuations•Very steady and accurate configuration•Cylindrical configurationconcentric massesoverlapping electrodes along X linearity

Spin ElectrodesSpin Electrodes

Radial ElectrodesRadial Electrodes

Axial ElectrodesAxial Electrodes

Digital

Pos Det ADC ControlLaws

DACDVA

Drag Free Control

Science Data

PM

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DVA (-) DAC

ADC

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Precise test-mass servo positioning thanks to• accurate machining• accurate metrology and integration• low noise electronics• thermal stability

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Payload 35 kg, 40 Watts : 2 similar instruments, each including one pair of masses : 2 pairs of masses : Pt / Pt & Pt / Ti Double difference of four inertial sensor outputs Scientific data & AOCS data for pointing and continuous drag compensation

Test-Masses

Silica cylinders for electrodes set

Vacuum system

Blocking system

Circuit boards for coax. connections

Hermetic connectors

Base plate assembly for high accurate positioning

24 bars chamber

Electro-valves

MICROSCOPE instrument configuration see for details presentation by Manuel Rodrigues


Geometrical AccuracyThermal Stability and Weak AgingConductivityIntegrationOff gassing- Out gassingVibration Resistance

SENSOR UNITsee for details presentation by Vincent Lebat


T-SAGE Payload Configurationsee for details presentation by Damien Boulanger

Mecanical sensor core :2 Differential accelerometers

mounted on 1 reference plateeach one contains 2 coaxial inertial sensorsno electronics, only wiring

weak power dissipation

Front End Electronics :•2 FEEU Units, one per accelerometer including:

Low noise analogue electronicsAnalogue to Digital ConversionDigital to Analogue Conversion

Interface Control Units : •1 Unit stacking 2 ICU (1 for each FEEU) with independent electrical functions: Digital control laws & Interfaces with the Satellite buses

OBCPCDU

0.3 K/Hz1/2

1mK @ fep

3.0 K/Hz1/2

5mK @ fep

± 4 °C


INSTRUMENT QUALIFICATION : achieved in 2012see for details presentation by Hans Selig and Françoise Liorzou

Verification of the operation in free fall tests with dedicated electronics :• mass levitation & servo-loops dynamics• bias levels• electrical interfaces between Sensor & sensitive electronics units• resistance to launch vibrations & thermal cycling• resistance to pyro chocks

Free-Fall in ZARM Bremen Tower

Chocks

Vibrations

Thermal cycling


MICROSCOPE Satellitesee for details presentation by Alain Robert, Michel Bach

2 differential accelerometers in thermal cocoon

2 differential accelerometers in magnetic cocoon

payload at the center of the satellite :-for thermal stability-for spin mode-for self gravity

X

Z Y

payload and star sensor for attitude control


MICROSCOPE Satellitesee for details presentation by Michel Bach

2 differential accelerometers in thermal cocoon

2 differential accelerometers in magnetic cocoon

payload at the center of the satellite :-for thermal stability-for spin mode-for self gravity

X

Z Y

payload an star sensor for attitude control


Drag free and Sensor control loops : Principlesee for details presentation by Pascal Prieur

~ a few Hz

ProofMass

Inertial Sensor

SatelliteThrusters

ThrusterActuators

[f1 – f2 Hz]

Capacitive positionsensors

Electrostaticactuators

PID

Estimators & Control Laws

Inertial sensor control loop

Drag compensation& attitude control loops

ADC+ PID

DAC

electrostatic loops

Instrument operation and reduction of perturbationsMass Off-Centering & Earth Gravity Gradient

Eccentricity < 5.10-3

+ S/C position tracking (Doppler) & GPS + Pointing, 10-3 rad with variations

Mass Off-Centering & Satellite Attitude Control Angular velocity variations Angular accelerations variations

Sensitivity Matching & linearity Drag-Free Control

Instrument calibration


EP Test Performance evaluationsee presentation by Ratana Chhun, Gilles Métris

Electronics: Verified on FM - Sensor accuracy and integration verified on QM Drop tower tests Demonstration of control laws operation & automatic acquisition before & after vibrations Expected Performance: better than 10-15

2 operating Satellite Modes :Rotating & Inertial modes fep

different kinetic conditions different thermal conditions Instrument

Performance evaluation from :Instrument error budgetSatellite drag compensation & attitude control performanceCalibration performanceEarth gravity gradient correction accuracy

Budget sub divided into more than 100 contributorsMission : More than 60 contributorsStochastic errors (colored noise) and systematic errors (tone errors at the frequency of the test)

Accuracy of the EP Test Specs of sensor unitelectronicsinstrument environmentmeasurement corrections Specs of satellite sub-systems

attitude & position recoveryin orbit calibration

Sensor Unit : •geometry•electrical & magnetic properties•thermal behavior•vacuumQM model performance

Analog electronics : gain, bandwidth, noise, linearity, thermal sensitivitiesDigital electronics :conversion accuracy, rate, computation accuracyFEEU FM model performanceICU EM model performance

Previous instruments performance & modelsSpecific experimental investigations

Equipment performancesAnalytical computationsSoftware Simulations

P.Touboul, 2009, Space Sci. Rev.


EP Test Performance validation see for details presentations by Ratana Chhun, Gilles Métris

2 operating Satellite Modes :Rotating & Inertial modes fep

different kinetic conditions different thermal conditions Instrument

DEMONSTRATION of Performance evaluation from :Instrument error budgetSatellite drag compensation & attitude control performanceCalibration performanceEarth gravity gradient correction accuracy

Accuracy of the EP Test Specs of sensor unitVALIDATION electronics

instrument environmentmeasurement corrections

Specs of satellite sub-systemsVALIDATION attitude & position recovery

in orbit calibration

Previous instruments performance & modelsSpecific experimental investigations

Equipment performances VALIDATIONAnalytical computationsSoftware Simulations

Sensor Unit : •geometry•electrical & magnetic properties•thermal behavior•vacuumFM model performance VALIDATION

Analog electronics : gain, bandwidth, noise, linearity, thermal sensitivitiesDigital electronics :conversion accuracy, rate, computation accuracyFEEU FM model performance VALIDATIONICU EM model performance VALIDATION


SPACE EXPERIMENT CONTROL & VALIDATIONsee for organization presentation by P.Y. GUIDOTTI

SATELLITE CONTROLCENTER

CNES Toulouse

SCIENTIFIC MISSIONCENTER

Onera Palaiseau

Satellite OperationPayload OperationMission Scenario ExecutionTM/TCExpertise

Payload SurveyData Quick-look SurveyMission Scenario Definition & UpdateExpertiseData processing, corrections & validationsData archivingData distributionsExperiment results & Phenomenology

Organization Rules and responsibilitiesInterfacesOperations & Software


Thanks to MICROSCOPE present partners

Physikalisch-Technische

Bundesanstalt

Observatoire de la Côte d’Azur

1 10 4 1 10 3 0.011 10 18

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Calibrated centringNon Calibrated1E-15 EP signal @ 730km

Hz

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n (m

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1 10 4 1 10 3 0.011 10 18

1 10 17

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Calibrated centringNon Calibrated1E-15 EP signal @ 730km

Hz

Diff

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tial A

ccele

ratio

n (m

/s²)


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MICROSCOPE mission overview - OCA

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