View
221
Download
5
Category
Preview:
Citation preview
MICROSCOPE: preliminary data processing methods
R. Chhun, E. Hardy, A. Levy, M. Rodrigues, P. Touboul (ONERA)
G. Métris (OCA)
From Quantum to Cosmos 5 (11/10/2012)
2
Contents
• The EP test in space• MICROSCOPE mission and instrument• Mission scenario• Data description• Data post-processing• Scientific activity and ground segment
3
Equivalence Principle
All bodies, independently of their mass or intrinsic composition, acquire the same acceleration in the
same uniform gravity field
Gravitational mass = Inertial mass
Newton:
Universality of free fall
General relativity can not merge gravitation with quantic mechanicsA new model is necessary:New interactions? New particles?String theory and supersymmetry?Space dimension >4?All these approaches ask for a violation of the equivalence principle at some level (10-14 to 10-21….)
Cstmm
i
g ga amgm ig
Einstein, 1907GR, 1916
Today
4
EP Testing in Space
On ground: • Seismic vibration (Earth, human activity) ~ µg• Local gravity to be compensated• Earth gravity gradient variations• Duration and measurement frequency difficult to master
“Free fall” test in space:• Vibrations reduced by several orders of magnitude ~ nano-g• Field sources = Earth + reduced local gravity• Measurement frequency = very well known orbital frequency• Very long fall duration (several orbits)• Dedicated instrument with sufficient limited range because in free fall• Highly stable thermal conditions
5
The MICROSCOPE Test of Universality of Free Fall
Inertial or spinningsatelliteMeasurement axisProof masses:material 1 (Pt)material 2 (Ti)Acceleration
• Servo-controlled concentric masses in the same gravitational field
• Measure of acceleration needed to maintain the two masses on the same orbit
• Differential acceleration ≠ 0 EP violation
• 2 differential electrostatic accelerometers (2 pairs of masses : Pt/Pt & Pt/Ti)
Measurement axis
6
Star Sensor
Drag
Solar Panels
Microthrusterpods
CNES MYRIADE CNES MYRIADE MicrosatelliteMicrosatelliteLaunch scheduled for 2016Circular Orbit : 720 km Inertial orbit or with satellite rotationMission duration : 11 monthsMicrosat : 200 kg, 1m3
Payload budgets : 35 kg, 40 Watts4 3 cold gas microthrustersContinuous drag compensation system
and orbit/attitude controlPassive thermal control
MICROSCOPE Mission Main Parameters
7
Instrument Description
360 x 348 x 180 mm3 x 20kgMechanical thermal model
• 2 differential accelerometers = 2 pairs of test-masses relatively centered at better than 20µm after integration• Integrated inside highly insulated thermal case• Integrated inside a µmetal magnetic shield• Rigidly linked to the satellite star sensor
Vacuum System
Blocking System
External Acc Electrode Cylinders
External PM(PtRh10 or TA6V)
Internal PM (PtRh10)
Internal AccElectrode Cylinders
• Proof masses with spherical inertia minimize effects of gravity gradient
• Electrode cylinders in gold-plated silica thermal geometrical stability
• Electrostatic control of 6 degrees of freedom of each mass steady configuration
• Retractable stops mass blocked during launch limited electrical disturbances
• Tight housing with getter material vacuum (<10-5 Pa)
• Invar housing matched CTE with silica + magnetic
shielding complementary to µmetal global
magnetic shield
1 differential accelerometer
External inertial sensor
Internal inertial sensor
8
The measure The measure Earth, satellite, instrument, physics contributionsEarth, satellite, instrument, physics contributions
Stochastic and Tone Signals to be considered with a limited observation period and missing data Detailed Specifications for S/C Sub-Systems, Instrument Environment & Instrument Performances Accurate in orbit calibration A posteriori estimation and corrections
czcxcxcycy
cxcxcyczcz
cycyczczcx
KK
K
dndmeasquadcappdsatcddmeas MOgCorInTMK ,,,,0, )(..2
Measured Differential Acceleration
Bias differencelimited thermal
fluctuations
Common Mode Sensitivity Matrix (Inst. Scale Factor &
Attitude, Coupling)Estimated by calibration
or limited by construction
Earth Gravity gradient tensorComputed with
model, S/C position & attitude,
and removed
Inertia Tensor (Angular Velocity and
Acceleration)Minimized by AOCS
from 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)
Instrumentnoise
2 2
2 2
2 2
y z x y z x z y
x y z x z y z x
x z y y z x x y
In
dzdxdxdydy
dxdxdydzdz
dydydzdzdx
KK
K
Coriolis tensor
0
00
z y
z x
y x
Cor
Quadratic residue
1
1
2
2
I
g
I
g
mm
mm
EP violation Masses excentring
9
Requirements and constraints
What must be done:• Acquire precise measurements for the EP test in varied experimental conditions:
• Inertial pointing instrument: different phases• Rotating Instrument: different velocities• Re-centered proof-masses or not
• Validate performance:• Accurate calibration in flight of the main parameters (sensitivity matrices…)• Fine characterization of instrument behavior with respect to thermal experimental
conditions…
Constraints :• Limited gas quantity for propulsion
• Need to establish priorities• No improvisation during mission flow
• Operational Security:• Need to foresee what to do and how to do it• Different EP test, calibration, characterization sessions: new session types not impossible but
limited • Mission scenario is a flowchart of sessions: flexibility at medium and long term
1010
Mission scenario: minimum and expected
S/C & payload Operation Verification & Adjustment
Preliminary Tests andEP Inertial sensor calibration
EP Tests with andwithout mass centering
Calibrations of bothEP and REF Instrument
REF Tests with andwithout mass centering
Additional EP Tests& calibration
REF Instrument new calibrationfor stability verif.
SUREF = Pt - Pt : SUEP = Pt - Tis
11
Data levels
• N0 level data : operational
• N1 leval dataCalibrated acceleration measurements per inertial sensor+ Complementary mission support data:orbit, attitude, acceleration and gravity gradient…
• (N1a) : reference calibration, fixed for the whole missionduration “raw” data for independent analysis
• (N1b) : Latest validated calibration phase data calibrated with as little “scientific bias” as possible
• (N1c) : calibration considered the most pertinent (time evolution, thermal evolution…) Best data but impacted by calibration choice
+ data necessary for the interpretation of the experiment…
• N2 level dataDifferential accelerations with correction of the gravity gradient effect among others + EP violation (or not)
• (N2a) : derived from (N1a), corrected of gravity gradient and excentrings estimated on ground• (N2b) : derived from (N1b), idem using excentrings estimated from test session data• (N2c) : derived from (N1c), idem using most relevant estimated excentrings and corrected of additional effects
with respect to the sensitivity of the instrument to its environment
Type Vol.%
Data description
ALIM 0.23 Battery charge, equipment current/voltage measurements, temperatures
SCAA/MCA
57.64 Attitude SST in J2000, Command outputs SCAA, guidance, combination TM T-SAGE for SCAA
CGPS 12.84 Cold gas propulsion system HK
OBC 0.01 Status bits of OBC and its components (FPGA, CPU…)
TTC 0.04 Antenna status
CU 28.73 T-SAGE 4Hz et 1 Hz data (angular et linear acc., position sensors, temperatures, reference voltages,
statuses….)
Thermi. 0.04 Platform temperature
GestionBord
0.16 TM, TC handling, modes, work plan, ….
Equipmt 0.01 SST raw data, inertia wheel
GNSS 0.3 GPS data (if present)
12
Data exploitation time scales
Different time scales with different flexibilities:• 1-week horizon: operational loop
• Verification of data integrity by automated processing• Mission program fixed (except potential stop or extension of a long session)
• 1-month horizon:• Preliminary analysis of data• Scenario still modifiable, in the frame of the predefined sessions
• 1-year horizon:• Detailed scientific analysis• Detailed performance analysis• Optimization of calibration processing• Application of data correction models
13
Influence of the observation window
TF TF
• Aliasing: a perturbation at any frequency has a component at the EP violation frequency (fEP)
EP violation signal:
Projection rate of a perturbation on the EP violation signal at fEP:
EPEP
dEP
SSSS
,,
)sin( EPEPEPEP tAS
)sin( dddd tAS Disturbance signal:
10-5 10-4 10-3 10-2 10-1
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
fdfréquence du signal perturbateur
Pro
ject
ion
max
imis
ée p
ar ra
ppor
t aux
pha
ses
Gabarit à fEPInertiel - 120 orbites
ProjectionSpécification
fEP
14
Main disturbances: due to the orbital or spin motion, n1forb+n2fspin→ choice of fspin and Tobservation to have minimal projection rates:
- Tobservation = k1.Torb- Tobservation = k2.Tspin
Choice of the measurement duration and spin frequency, special specifications
To distinguish forb and fEPk2 = 73
to reduce the noisek1 = 20k1 = 120Spinning modeInertial mode
10-5 10-4 10-3 10-2 10-110
-8
10-6
10-4
10-2
100
fd
fréquence du signal perturbateur
Pro
ject
ion
max
imis
ée p
ar ra
ppor
t aux
pha
ses
Gabarit à fEP
Inertiel - 120 orbites
ProjectionSpécification
fEP
Influence of knowledge and realization error:- Knowledge on the orbital frequency : 2.10-8rad/s (↔ 100m for the orbit altitude)- Command error on the spin frequency: 3.10-8rad/s- Realization error on the inertial pointing: 1.10-8rad/s
3.3182 3.3182 3.3183 3.3183 3.3183 3.3183 3.3183 3.3184
x 10-4
10-7
10-6
10-5
10-4
2forbestimée
2forbréèlle
Not 0!
15
Non-rectangular windows
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Fenêtres temporelles
t
fenêtre rectangulairefenêtre de Hannfenêtre de Hammingfenêtre de Blackman
-0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.050
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Transforméee de Fourier des fenêtres
f
fenêtre rectangulairefenêtre de Hannfenêtre de Hammingfenêtre de Blackman
10-5 10-4 10-3 10-2 10-110-18
10-16
10-14
10-12
10-10
10-8
10-6
10-4
10-2
100
fd : fréquence du signal perturbateurP
roje
ctio
n m
axim
isée
par
rapp
ort a
ux p
hase
s
Gabarit à fEP
Inertiel - 120 orbites
fenêtre rectangualairefenêtre de Hammingfenêtre de Hannfenêtre de Blackmanspécification
10-3.79 10-3.78 10-3.77
100
fdfréquence du signal perturbateur
Pro
ject
ion
max
imis
ée p
ar ra
ppor
t aux
pha
ses
Gabarit à fEPInertiel - 120 orbites
fenêtre rectangulairefenêtre de Hammingfenêtre de Hannfenêtre de Blackmanspécification
Comparison between different windows: important improvement, except around fEP
TF
16
Error budget
• Rejection rates induced errors
• Attitude control error budget
• Pointing, angular velocity and angular acceleration control performance / specifications among ~60 contributions
• Mission error budget
Error general form (in mesd)
0 Md x T x OdfpO in DF res.acc. 0.00E+00 0.0% 0.00E+00 0.0%1 1/2 x (I+Mc) x (T x res + Tres x ) 7.27E-16 0.0% 7.78E-16 13.9%2 1/2 x ( TTres+resTres
T) 9.02E-19 0.0% 1.37E-15 24.4%3 Instrument self gravity (wrt thermal stability) from finite elements model 6.00E-14 1.3% 2.00E-16 3.6%4 Satellite Gravity in DF residual acceleration 0.00E+00 0.0% 0.00E+00 0.0%5 Md x Tsc x OdfpO in DF res.acc. 0.00E+00 0.0% 0.00E+00 0.0%6 1/2 x (I+Mc) x Tsc x 1.21E-13 2.6% 3.04E-16 5.4%7 Md x 2 x OdfpO in DF res.acc. 0.00E+00 0.0% 0.00E+00 0.0%8 1/2 x (I+Mc) x 2 x 1.62E-17 0.0% 8.05E-17 1.4%9 Md x d/dt x OdfpO in DF res.acc. 0.00E+00 0.0% 0.00E+00 0.0%
10 1/2 x (I+Mc) x d/dt x 2.02E-13 4.3% 4.05E-16 7.2%11 in DF residual acceleration 0.00E+00 0.0% 0.00E+00 0.0%12 1/2 x (I+Mc) x x d/dt 4.15E-19 0.0% 2.91E-20 0.0%13 in DF residual acceleration 0.00E+00 0.0% 0.00E+00 0.0%14 1/2 x (I+Mc) x d2/dt2 3.13E-16 0.0% 1.05E-18 0.0%15 in DF residual acceleration 0.00E+00 0.0% 0.00E+00 0.0%16 1/2 x (I+Mc) x (T+Tsc+2+d/dt) x 4.39E-16 0.0% 3.41E-18 0.1%17 d x c 5.72E-14 1.2% 0.00E+00 0.0%18 c x d 3.31E-14 0.7% 2.76E-16 4.9%19 d x (c + Binst) 1.80E-13 3.8% 0.00E+00 0.0%20 c x (d + Binst) 5.00E-13 10.6% 0.00E+00 0.0%21 d x (c + Binst) 2.05E-13 4.3% 0.00E+00 0.0%22 c x (d + Binst) 1.41E-13 3.0% 0.00E+00 0.0%23 Accelerometer measurement noise Instrument error budget 3.29E-12 69.5% 0.00E+00 0.0%24 Bias sensitivity to SU temperature variation dBinst/dTmec x Tmec 6.06E-13 12.8% 2.02E-15 36.1%25 Bias sensitivity to FEEU temperature variation dBinst/dTelec x Telec 1.01E-13 2.1% 1.01E-15 18.0%26 dd/dTmec x Tmec x (c) 8.58E-14 1.8% 4.02E-16 7.2%27 dc/dTmec x Tmec x (d) 6.32E-18 0.0% 4.54E-20 0.0%28 dd/dTelec x Telec x (c) 1.43E-14 0.3% 2.01E-16 3.6%29 dc/dTelec x Telec x (d) 1.05E-18 0.0% 2.27E-20 0.0%30 dKd/dTmec x Tmec x (c+Binst_c) 1.44E-13 3.1% 4.80E-17 0.9%31 dKc/dTmec x Tmec x (d+Binst_d) 1.20E-13 2.5% 3.69E-16 6.6%32 dKd/dTelec x Telec x (c+Binst_c) 1.20E-13 2.5% 1.20E-16 2.1%33 dKc/dTelec x Telec x (d+Binst_d) 1.00E-13 2.1% 1.00E-15 17.9%34 dd/dTmec x Tmec x (c+Binst_c) 1.23E-13 2.6% 5.79E-16 10.3%35 dc/dTmec x Tmec x (d+Binst_d) 8.49E-14 1.8% 4.00E-16 7.1%36 dd/dTelec x Telec x (c+Binst_c) 2.05E-14 0.4% 2.89E-16 5.2%37 dc/dTelec x Telec x (d+Binst_d) 1.41E-14 0.3% 2.00E-16 3.6%38 Bias sensitivity to SU thermal gradient variation dBinst/dgradT x gradT 1.20E-12 25.4% 2.00E-15 35.7%39 Satellite positioning 1/2 x dT x 5.27E-17 0.0% 3.00E-16 5.4%40 Timing error 1/2 x T x 3.54E-17 0.0% 1.59E-16 2.8%41 Synchronisation error ep x t x c + ep x t x c 5.28E-19 0.0% 1.10E-18 0.0%42 DF residual acceleration Md x Resdrag 9.95E-14 2.1% 5.00E-16 8.9%43 Magnetic field (Earth+local) effect Analysis 8.00E-14 1.7% 4.00E-16 7.1%44 Radial measurement noise introduced by data processing (d+d)est x ninst_c 3.20E-13 6.8% 0.00E+00 0.0%
45 Radial bias sensitivity to SU temperature variation introduced by data processing (d+d)est x dBinst_c/dTmec x Tmec 1.36E-13 2.9% 6.40E-16 11.4%
46 Radial bias sensitivity to FEEU temperature variation introduced by data processing (d+d)est x dBinst_c/dTmec x Telec 2.26E-14 0.5% 3.20E-16 5.7%
47 Radial bias sensitivity to SU thermal gradient variation introduced by data processing (d+d)est x dBinst_c/dgradT x gradT 1.36E-13 2.9% 3.20E-16 5.7%
48 Accelerometer angular noise x acc_ang 5.52E-15 0.1% 0.00E+00 0.0%49 Angular attitude control variations x d/dt 1.06E-14 0.2% 3.00E-17 0.5%50 Angular bias sensitivity to SU temperature variation x dacc_ang/dTmec x Tmec 3.18E-16 0.0% 1.50E-18 0.0%51 Angular bias sensitivity to FEEU temperature variation x dacc_ang/dTmec x Telec 7.42E-16 0.0% 1.05E-17 0.2%52 Angular/linear coupling noise x angular accelerometer bias x acc_ang 1.48E-13 3.1% 0.00E+00 0.0%53 Angular/linear coupling noise x attitude control bias x d/dt 8.49E-15 0.2% 0.00E+00 0.0%54 Ang/Lin coupling sensitivity to SU temperature variation d/dTmec x acc_ang x Tmec 8.91E-14 1.9% 4.20E-16 7.5%55 Ang/Lin coupling sensitivity to SU temperature variation d/dTmec x d/dt x Tmec 5.09E-15 0.1% 2.40E-17 0.4%56 Ang/Lin coupling sensitivity to FEEU temperature variation d/dTelec x acc_ang x Telec 0.00E+00 0.0% 0.00E+00 0.0%57 Ang/Lin coupling sensitivity to FEEU temperature variation d/dTelec x d/dt x Telec 0.00E+00 0.0% 0.00E+00 0.0%58 K2c x appc x appd 4.20E-13 8.9% 1.29E-15 23.0%59 K2d x (appc
2 + appd2) 5.05E-13 10.7% 1.68E-16 3.0%
TOTAL (direct sum)/3 5.55E-15 99.0%TOTAL (quadratic sum) 3.71E-12 78.3%
SPECEP 8.93E-16
tone @fep (m/s²) in 2mesd
Coupling sensitivity to FEEU temperature variation
Alignment sensitivity to SU temperature variation
Alignment sensitivity to FEEU temperature variation
Scale Factor sensitivity to SU temperature variation
Scale Factor sensitivity to FEEU temperature variation
Alignment (not thermal stability)
Coriolis (wrt thermal stability)
PM average and relative positions (wrt thermal stability)
noise (m/s²/Hz^1/2) in 2mesd
4.73E-12
noise (m/s²/Hz^1/2) in 2mesd
5.60E-15
Quadratic factor
tone @fep (m/s²) in 2mesd
Coupling (not thermal stability)
Coupling sensitivity to SU temperature variation
Earth Gravity Gradient
PM average and relative accelerations (wrt thermal stability)
Satellite Gravity Gradient
Centrifugal acceleration
Angular acceleration
Scale Factor (not thermal stability)
TOTAL (direct sum)/3 5.55E-15 99.0%TOTAL (quadratic sum) 3.71E-12 78.3%
SPECEP 8.93E-16
4.73E-12
noise (m/s²/Hz^1/2) in 2mesd
5.60E-15
tone @fep (m/s²) in 2mesd
17
Measurement loss
• Teletransmission errorsInformation from Picard mission:• frequency: about 100 events over 10 months• duration: from seconds to hours
• Coating cracking• due to temperature changes (Earth / Space vacuum)• frequency: for each of the four satellite sides, about 6 times
when the side faces the Earth• duration: 0.5-0.75s 2 - 3 measurement points
• Tank cracking• worst case, depending on gas pressure• frequency: for each of the 6 tanks, about 43 times/orbit• duration: 0.5s 2 measurement points
18
Measurement loss
• Without measurement loss:
TF(S) = TF( )*TF( )• With measurement loss: replacement by zeros
TF(S) = TF( )*TF( )• With measurement loss: replacement by the mean value of the measurement before and after the interruption
TF(S) = TF( )*TF( )
19
Short duration loss
- one measurement loss
- simulations with different duration
- respect the specifications up to 1 minute
No measurement loss
First method: replacement by zeros
Second method: replacement by the mean value before and after the interruption
20
Division into subsections
16% Not acceptableInertial session: 120 orbits2,9% AcceptableSpinning session: 20 orbitsProbability of failureActivity
With the measure replacement procedure, session failure criterion: more than 1 measurement loss of duration > 1 minute per session
For data losses > 1 minute in inertial session (and < 1 orbit): → inertial session of 120 orbits divided into several subsections
- Tsubsection,i = niTorb (rejection of the main perturbations)
Need to consider an alternative correction method
+ additional orbits
21
Division into subsections
0,07%40.4%32,5%216%1
Probability over 120 orbits
Number of data loss > 1 minute and < 1 orbit
Success probability > 99,9%
10-5 10-4 10-3 10-2 10-110-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
fdfréquence du signal perturbateur
Pro
ject
ion
max
imis
ée p
ar ra
ppor
t aux
pha
ses
Gabarit à fEP en inertiel
Cumul de 4 sessions séparées de 1 orbite
20 orbites + 20 orbites + 40 orbites + 40orbites20 orbites + 20 orbites + 20 orbites + 60 orbitesSpécification Method is robust up to 3
losses considering a worst case distributionOver 4 losses, success depends on losses distribution
3 losses, 2 distributions
22
Data post-processing summary
• Influence of the observation window• Perturbations at any frequency can have a component at the EP
frequency• Main perturbations frequencies: adjusted to have minimal projections,
but effects are amplified by frequency knowledge and realization• Numerical estimation of the projection rate: compatible with the
specification• Influence of the measurement losses on the projection and
rejection rate• Numerous very small losses or one larger loss up to 1 minute:
replacement by the mean value of the measurement before and after the interruption
• Losses > 1 minute: division in separated subsections for the inertial sessions
• Acceptable probability of success for the mission• Possibility of accuracy improvement using Hann or Blackman
window.
23
Operational and scientific organization
GEX: Group of ExpertsSPG: Scientific Performance GroupSWG: Science Working group
24
Ground segment architecture
SPG
25
Development of the scientific activity around MICROSCOPE
Scientific objectives:To obtain and validate results, to give the data as much credit as possible
• Phase 1: completing the existing team• Contribution to the present scientific team to reinforce/double the expertise for
the exploitation and validation of the experimental data• Contribution through a phenomenological approach allowing to test new
theories using MICROSCOPE experiment data in relation with the present scientific team
• Exploitation of data provided by the mission for scientific objectives other than the EP test
• Phase 2: critical and independent exploitationAfter validation of experimental data, exploitation and interpretation of MICROSCOPE data, independent of the present team
26
Conclusion
Cooperation and data sharing are necessary to reinforce validation and open up the scientific exploitation
Scientific teams already envisaged will be contacted starting this year MICROSCOPE Colloquium II scheduled 28th and 29th of January, 2013 (TBC):
detailed presentation of the mission and data invitation to scientists to present their concrete interests and competences
The organization of the different operational/scientific groups is formalized and is to be validated by CNES
The schedule for the setting of this community and the activities is proposed till launch mid-2016
The MICROSCOPE SWG is actor in:The exploitation of experimental data, The phenomenological developments and the exploitation of the EP test,The exploitation of data for other scientific exploitations,The encouragement toward the scientific community for the exploitation of the MICROSCOPE
mission
Recommended