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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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slide1

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

slide2

Outline

1

Motivation and Strategy

2

Scheme and Error Budget

3

Current Progress at HUST

4

Roadmap and Conclusion

slide3

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
slide4

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

slide5

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

slide6

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

slide8

10-m Prototype of Laser Ranging System

Installed at HUST (2009~2010)

5-nm step

Driving by PZT stage

slide9

FPGA-Based Digital Phasemeter (2010~2011)

210-5 rad/Hz1/2@0.1Hz

Phase (peak-to-peak) = 0.01o 30pm

slide10

amplitude: 25 pm

Ultra-Stable Optical Bench (2011-2012)

Cooperation with AEI, Hannover

slide11

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

slide12

Laser Frequency Stabilization

F-P cavity for

Laser frequency stabilization

  • Key factors:
  • Mechanical stability of cavity
  • Thermal stability of cavity
  • Environment control
  • Mode matching
slide13

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
slide14

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

slide15

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
slide16

Thank you

for your attentions!