Abstract
A Chinese satellite gravity mission called SAGM (Space Advanced Gravity Measurements) is now taken into consideration. To meet its designed requirement, the measurement precision of the laser ranging system used to measure the inter-satellite distance change has to be better than 100nm/Hz1/2 within a broad bandwidth from 0.1 mHz to 1 Hz. An equal arm heterodyne Mach-Zehnder interferometer has been built on ground to demonstrate the measurement principle of a laser ranging system, which potentially can be used for both SAGM and future GW (gravitational wave) space antennas. Because of the equal arm length, the laser frequency noise has been significantly suppressed in the interferometer. Thus, the sensitivity better than 1nm/Hz1/2 in a frequency range of 0.15 mHz–0.375 Hz has been achieved. The result shows that the proposed methodology has very promising feasibility to meet the requirements of SAGM and of GW space antennas as well.