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Current progress of developing Inter-satellite laser interferometry for

Current progress of developing Inter-satellite laser interferometry for Space Advanced Gravity Measurements. Hsien-Chi Yeh School of Physics Huazhong University of Science & Technology 22 May, 2012. Outline. 1. Motivation and Strategy. 2. Scheme and Error Budget. 3.

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Current progress of developing Inter-satellite laser interferometry for

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  1. Current progress of developing Inter-satellite laser interferometry for Space Advanced Gravity Measurements Hsien-Chi Yeh School of Physics Huazhong University of Science & Technology 22 May, 2012

  2. Outline 1 Motivation and Strategy 2 Scheme and Error Budget 3 Current Progress at HUST 4 Roadmap and Conclusion

  3. Motivation: Gravitational Waves Detection in Space • Orbit precession in the perihelion of planets • Deflection of light by solar gravity • Redshift of spectral lines • Frame dragging • Gravitational waves

  4. Sensitivity Requirements of GWD Missions 10-18 10-19 10-20 10-21 10-22 10-23 10-24 10-25 ASTROD (2A.U.) LIGO A-LISA (ALIA) (LISA type, 5105km) 10-5 10-4 10-3 10-2 10-1 100 101 102 103

  5. Strategy: Treat SAGM as LISA Pathfinder Space Advanced Gravity Measurements (SAGM) • 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

  6. Transponder-Type Laser Ranging System 200km Environment Control Environment Control Inertial Sensor Inertial Sensor Drag Free Control Drag Free Control Beam Collimation & Pointing Control Beam Collimation & Pointing Control Transponder With Phase- Locked Loop Heterodyne Laser Interferometer Proof Mass Proof Mass Inertial Sensor Inertial Sensor Satellite Platform Satellite Platform

  7. Error Budget

  8. 10-m Prototype of Laser Ranging System Installed at HUST (2009~2010) 5-nm step Driving by PZT stage

  9. FPGA-Based Digital Phasemeter (2010~2011) 210-5 rad/Hz1/2@0.1Hz Phase (peak-to-peak) = 0.01o 30pm

  10. amplitude: 25 pm Ultra-Stable Optical Bench (2011-2012) Cooperation with AEI, Hannover

  11. Transponder-Type Laser Ranging (2012) Displacement output Phase Locked Control Phase Meter Weak-light: 10 nW Proof Mass Proof Mass Optical Bench Optical Bench Master laser PZT Slave laser Homodyne OPLL 1-nm sinusoidal motion

  12. Laser Frequency Stabilization F-P cavity for Laser frequency stabilization • Key factors： • Mechanical stability of cavity • Thermal stability of cavity • Environment control • Mode matching

  13. Beam Pointing Angle Measurement • Contrast Measurement • Divergence angle：10-4 rad • Received power：10-8 W • Contrast  misalignment angle • precision：10-5 rad • Phase-difference Measurement • Divergence angle：3.510-5 rad • Received power：10-7 W • Phase difference  misalignment angle • precision：10-7rad • Jitter：10-6rad/Hz1/2

  14. Proposed Timeline • 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 • Inter-Satellite Laser Ranging • For 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 2020 2025 2010 2015 2030

  15. Conclusions • 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

  16. Thank you for your attentions!

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