Hsien-Chi Yeh, Qi-Zhong Yan, Yu-Rong Liang, Ying Wang, and Jun Luo
School of Physics, Huazhong University of Science and Technology, 1037 Luo Yu Road, Wuhan
School of Optoelectronic Science and Technology, Huazhong University of Science and Technology,1037 Luo Yu Road, Wuhan
(Received 5 January 2011; accepted 9 March 2011; published online 12 April 2011)

Abstract:
      In this paper, we present the scheme and the preliminary results of an intersatellite laser ranging system that is designed for the Earth’s gravity recovery mission proposed in China, called Space Advanced Gravity Measurements (SAGM). The proposed intersatellite distance is about 100 km and the precision of inter-satellite range monitoring is 10 nm/Hz1/2 at 0.1 Hz. To meet the needs, we designed a transponder-type intersatellite laser ranging system by using a homodyne optical phase locking technique, which is different from the heterodyne optical phase-locked loop used in GRACE followon mission. Since an ultrastable oscillator is unnecessary in the homodyne phase-locked loop, the measurement error caused by the frequency instability of the ultrastable oscillator need not be taken into account. In the preliminary study, a heterodyne interferometer with 10-m baseline (measurement arm-length) was built up to demonstrate the validity of the measurement scheme. The measurement results show that a resolution of displacement measurement of about 3.2 nm had been achieved.