Optical metrology applications at TAS-Ieotvos.dm.unipi.it/Workshop2010/Talks/Cesare.pdf · the...
Transcript of Optical metrology applications at TAS-Ieotvos.dm.unipi.it/Workshop2010/Talks/Cesare.pdf · the...
GG workshop
12/02/2010 2/26/2008, Thales Alenia Space
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INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE
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Optical Metrology Applications at TAS-I in support of Gravity and Fundamental Physics
Stefano Cesare, Thales Alenia Space Italia, Torino
Workshop “GG/GGG: state of the art and new possibilities”Pisa, 12 Febbraio 2010
2/26/2008, Thales Alenia Space
GG workshop
12/02/2010
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Optical metrology at TAS-I
Main research projects and applications of optical metrology at TAS-I:
Monitoring of the GAIA astrometric instrument stability (1997 –2003).Co-phasing of optical interferometers (2002 – 2006).Satellite-to-satellite laser tracking for Next Generation Gravity Missions (2004 – present).Nanobalance facility for characterization of micro-Newton thrusters (2001 – present).
Collaborations:
Istituto Nazionale di Ricerca MetrologicaPolitecnico di TorinoINAF – Osservatorio Astronomico di Torino
2/26/2008, Thales Alenia Space
GG workshop
12/02/2010
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Metrology for GAIA astrometric instrument
0 100 200 300 400-2
-1
0
1
2
3x 10-12
Time [s]
Dis
tanc
e va
riatio
n [m
]
IFR signal: Control error
2/26/2008, Thales Alenia Space
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Co-phasing of optical interferometers
Breadboard of a two-aperture optical interferometer with its co-phasing system, for the development project of a synthetic-aperture optical telescope. Fringe Sensor Unit realized for the co-phasing of
the VLTI (ESO). Operative at Cerro Paranal, Chile.
2/26/2008, Thales Alenia Space
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The distance variation between two satellites (∆d) is measured by a laser metrology system.The distance variation between the satellites produced only by drag forces (∆dD) is measured by accelerometers.
Subtracting (∆dD) from (∆d) the distance variation produced by the gravity acceleration is obtained: ∆dG = ∆d - ∆dD
Satellite 2 Satellite 1
g2 g1
d
∆d = ∆dG+ ∆dD
Earth
FD2 FD1D2 D1
Requirement for the laser interferometer measurement noise (relative distance = 10 km)
Satellite-to-satellite laser tracking for NGGM
1 10 4 0.001 0.01 0.1 11 10 9
1 10 8
1 10 7
1 10 6
frequency [Hz]
rela
tive
dista
nce
erro
r SD
[m/s
qrt(
Hz)
]
.1 10 3 10 1
2.26 nm/√Hz
Gravimetry by satellite-to-satellite tracking
2/26/2008, Thales Alenia Space
GG workshop
12/02/2010
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Michelson-type heterodyne laser interferometer based on polarized beams, with chopped measurement beam to avoid spurious signals and non-linearity caused by the unbalance between the strong local beam and the weak return beam.Passive retro-reflection of the laser beam on S2: simple solution, suitable for d up to 100 km.
Optical metrology concept for the NGGM
λ2πδ
21δ φ
=L
ν2
pbs2 q1q2
p4
p3
ν1
p1
p2
RR1
l1
l2
c1
c2
ν2
ν0 ν1
f1
f2νm
ν0
ν'm
pbs1 pd1
bsAMFSLaser source
Frequency StabilisationSystem
BSM telescope
amplitudemodulated beam
RR2
Satellite 2
angle and lateral displacement sensors angle sensors
PSD1
PSD2
PSD3
PSD4
PSD5
PSD6
Satellite 1 pd2
L
Spd2 = 2I”⋅{1 + cos [2π(ν1-ν2)t + φ + δφ]}
Spd1 = 2I’⋅{1 + cos [2π (ν1-ν2)t + φ]}
Nd:YAG
1064 nm
Satellite-to-satellite laser tracking for NGGM
d
2/26/2008, Thales Alenia Space
GG workshop
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Satellite 2
Active optical bench(laser emission & interferometry)
Satellite 1Passive optical bench(laser retro-reflection)
Accelerometers
Interferometer core
Beam Steering Mechanism
Angular metrology
Angular/lateral metrology
Retro-reflector
Optical metrology arrangement on the satellites
The non-gravitational accelerations of the satellite COM can be measured by electrostratic accelerometers like those used on GOCE.
Satellite-to-satellite laser tracking for NGGM
2/26/2008, Thales Alenia Space
GG workshop
12/02/2010
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Laser interferometer breadboard prepared for the intrinsic noise test (measurement of a constant distance).
Spectral density of the distance variation measurement error obtained during the tests and compared to the requirement.
In order to achieve the specified measurement performance over a distance of 10 km, the laser frequency shall have a relative stability δν/ν ≤ 1.4⋅10-13 Hz-1/2.
Satellite-to-satellite laser tracking for NGGM
Interferometer BB test
2/26/2008, Thales Alenia Space
GG workshop
12/02/2010
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Interferometer BB test
Laser interferometer breadboard under the functional test over a long distance (~90 m) with a moving target. The effectiveness of the measurement beam chopping scheme was successfully verified in this test.
Satellite-to-satellite laser tracking for NGGM
2/26/2008, Thales Alenia Space
GG workshop
12/02/2010
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Open-loop test of the Lateral Displacement Metrology.Lateral displacement steps (from ±50 µm to ±5 mm) measured by the optical metrology at 10 Hz. Max. measurement error: 0.25 mm (over the largest steps)Max. measurement noise: 14 µm 1σ.
Test of the laser beam pointing control system BB.
Beam Steering Mechanism Angle/lateral Displacement
Metrology
Closed-loop test of the laser beam pointing control system (BSM driven by the Lateral Displacement Metrology measurements). Laser beam pointing stability results.
Satellite-to-satellite laser tracking for NGGM
2/26/2008, Thales Alenia Space
GG workshop
12/02/2010
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optical cavity
NanobalanceThrust Stand
optical head
alignmentdevice
thrusterunder test
vacuum chambertiltmeter
pneumaticsupport
horizontality control stage
beam trap
pumpgroup
optical fiber
metrology system
optical benchMonitoring and Control System
thermistor(s)
vacuometer
Thrust Stand
Nanobalance
The Nanobalance is a complete test facility for the direct measurement of the force provided by a micro-thruster along its thrust axis, developed by TAS-I for ESA.
2/26/2008, Thales Alenia Space
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A micro-thruster force F = 0.1 µN induces a distance variation betweenthe tilting plates δL ≅ 14 pm, corresponding to frequency variation of the laser locked to the Fabry-Perot cavity δνL ≅ 40 kHz.
Fabry-Pérot Cavity, L
elastic jointZERODUR®
Athermicspacer
Micro-Thruster under terst
Laser, vL
Passive Tilting Plate
elastic joint
Dummy Micro-Thruster
Actiive Tilting Plate
Fabry-Pérot Cavity, L -δL
elastic joint
ZERODUR®
Athermicspacer
Micro-Thruster under terst
Laser, vL + δvL
Passive Tilting Plate
elastic joint
Dummy Micro -Thruster
Actiive Tilting Plate
Thrust F
Nanobalance
2/26/2008, Thales Alenia Space
GG workshop
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Nanobalance
Power Spectral density of the measurement force noise after post-processing for removing the low-frequency drift effect.
10-4 10-3 10-2 10-1 100 10110-3
10-2
10-1
100
101
Frequency [Hz]
PS
D [ µ
N/ √
Hz]
10-4 10-3 10-2 10-1 100
Forc
e [µ
N/√
Hz]
Frequency [Hz]
100
101
10-1
10-2
10-3
NB background noise - PSD
10170 80 90 100 110 120 130
-0.2
0
0.2
0.4
0.6
0.8
1
Time [s]
Forc
e [ µ
N]
VC forceWide band filterNarrow band filter
NB Resolution
Applied ForceWide band meas.Narrow band meas.
Measured thrust corresponding to the smallest applied force steps with a voice coil actuator.
2/26/2008, Thales Alenia Space
GG workshop
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Nanobalance
Test of a cold-gas thruster
Applications:GAIA, Microscope (backup)
Applications:LISA PF, Microscope,GG
Test of a FEEP thrusterTest of a mini-RIT
Applications:NGGM, GG (backup)