Current progress of developing Inter-satellite laser interferometry for
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Current progress of developing Inter-satellite laser interferometry for
Space Advanced Gravity Measurements
Hsien-Chi Yeh
School of PhysicsHuazhong University of Science & Technology
22 May, 2012
Outline
11 Motivation and Strategy
22
Current Progress at HUST33
Scheme and Error Budget
Roadmap and Conclusion44
Orbit precession in the perihelion o
f planets Deflection of light by solar gravity Redshift of spectral lines Frame dragging
Gravitational waves
Motivation: Gravitational Waves Detection in
Space
Frequencyrange (Hz)
Arm lengthDisplacement
noise (pm/Hz1/2)Acceleration noise
(ms-2/Hz1/2)
LISA 10-4 ~ 10-1 5109 m 20 310-15 @1mHz
ALIA 10-3 ~ 1 ~ 5108 m ~ 0.1 ~ 310-16 @10mHz
ASTROD 10-6 ~ 10-3 ~ 31011 m ~ 2000 ~ 810-16 @0.1mHz
10-18
10-19
10-20
10-21
10-22
10-23
10-24
10-25
LIGO
A-LISA (ALIA)(LISA type, 5105km)
ASTROD(2A.U.)
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Sensitivity Requirements of GWD Missions
Strategy: Treat SAGM as LISA Pathfinder
Satellite-to-satellite tracking (SST):• Separation: ~100 km• Altitude: 250~300 km (declined orbit)• Measurement:
Laser interferometer (30~50 nm)GPS (1mm)
GRACE-like mission
Space Advanced Gravity Measurements (SAGM)
Transponder-Type Laser Ranging System
200km
BeamCollimation & Pointing
Control
ProofMass
Inertial Sensor
Inertial Sensor
HeterodyneLaser
Interferometer
Satellite Platform
EnvironmentControl
Dra
g F
ree
Con
trol Beam
Collimation & Pointing
Control
ProofMass
Inertial Sensor
Inertial Sensor
TransponderWith Phase-Locked Loop
Satellite Platform
EnvironmentControl
Dra
g F
ree
Con
trol
OPLL
MD
M cLt
cL
2)(
2
Error Source Error component
Pre-stabilized laser: f < 50 Hz/Hz1/2
L = 200 km 30.0 nm/Hz1/2
Thermal drift of O.B. (fused quartz):thermal variation: 0.01Kunbalanced OPL: 1 cm
2.0 nm/Hz1/2
Divergence angle of laser beam:div ~ 3.510-5 rad
Pointing control:dc ~ 10-5 rad, jit ~ 10-5 rad/Hz1/2
9.0 nm/Hz1/2
Phasemeter resolution 1.0 nm/Hz1/2
Residual error of OPLL 3.0 nm/Hz1/2
Shot noise and Ionosphere effect < 0.1 nm
(RSS) Total ~ 35 nm/Hz1/2
Error Budget
10-m Prototype of Laser Ranging SystemInstalled at HUST (2009~2010)
5-nm stepDriving by PZT stage
10-4
10-3
10-2
10-1
100
101
10-8
10-6
10-4
10-2
100
102
Ph
ase L
AS
D [
rad
*Hz
-1/2]
Frequency [Hz]
Noise in digital systemTwo 9.999MHz inputNoise level of GRACENoise level of LISA
FPGA-Based Digital Phasemeter (2010~2011)
1200 1220 1240 1260 1280 1300
-3.21
-3.208
-3.206
-3.204
-3.202
-3.2
-3.198
-3.196
-3.194
Time origin: 2011-06-15 17:30:00.000
Ph
ase
[deg
]
Time [s]
1.txt_01
Phase (peak-to-peak) = 0.01o 30pm
210-5 rad/Hz1/2@0.1Hz
Ultra-Stable Optical Bench (2011-2012)
Cooperation with AEI, Hannover
0 0.2 0.4 0.6 0.8 1-60
-40
-20
0
20
40
60
80Time origin: 2012-04-10 04:00:00.000
Dis
pla
cem
en
t [p
m]
Time [s]
PZT-4mVpp-step data after fitted polynomial taken out
Above data after smoothing with 4-point averageamplitude: 25 pm
Transponder-Type Laser Ranging (2012)
ProofMass
OpticalBench
ProofMass
OpticalBench
PhaseMeter
PhaseLockedControl
Maste
r la
ser
Sla
ve
lase
r
Displacement output
PZT
1-nm sinusoidal motion
1784 1785 1786 1787 1788 1789 17903.7646
3.7647
3.7648
3.7649
3.765
3.7651
3.7652x 10
4 Time origin: 2011-12-31 20:40:00.000
Dis
pla
cem
en
t [
nm
]
Time [s]
Displacement data with 1nm amplitude 1Hz sinewaveDisplacement data after filtered
Weak-light: 10 nW
Homodyne OPLL
Key factors:• Mechanical stability of cavity• Thermal stability of cavity• Environment control• Mode matching
F-P cavity forLaser frequency stabilization
Laser Frequency Stabilization
Beam Pointing Angle Measurement
Phase-difference Measurement• Divergence angle: 3.510-5 ra
d• Received power: 10-7 W• Phase difference misalignme
nt angle• precision: 10-7rad• Jitter: 10-6rad/Hz1/2
Contrast Measurement• Divergence angle: 10-4 rad• Received power: 10-8 W• Contrast misalignment angle• precision: 10-5 rad
2/)( BA
BA
II
IIcontrast
2010 20202015 2025 2030
Inter-Satellite Laser RangingFor Earth’s Gravity Recovery
• Inter-satellite distance: 50-200 km
• Sensitivity: 30-50 nm/Hz1/2
• Transponder-type heterodyne interferometry
• Pointing control: 10-6 rad/Hz1/2
Inter-Satellite Laser Interferometer
For Gravitational Waves Detection
• Inter-satellite distance: 105~106 km
• Sensitivity: < 1 pm/Hz1/2
• Transponder-type heterodyne interferometry
• Special methods to decompress laser frequency noise
• Pointing control: 10-9 rad/Hz1/2
Proposed Timeline
• GW detection (long-term goal)Earths gravity recovery (short-term goal):SAGM as our LISA Pathfinder
• Preliminary demonstration:transponder-type laser ranging with weak-light phase locking
• Focused tasks in the next step: (1) space-qualified frequency-stabilized laser(2) laser beam pointing measurement and control(3) simulation experiment of plasma in ionosphere
Conclusions
Thank youfor your attentions!
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