Studying an off-axis optical bench for future gravity missions from the perspective of carrier-to-noise ratio

The inter-satellite laser ranging heterodyne interferometer is vital for future gravity missions to achieve high ranging accuracy. This paper proposes a novel off-axis optical bench design which integrates merits of the off-axis optical bench design of GRACE Follow-On mission and other on-axis designs. This design makes use of lens systems subtly to restrict the tilt-to-length coupling noise and takes advantage of the DWS feedback loop to maintain the transmitting beam and receiving beam anti-parallel. The critical parameters of the optical components are determined and the carrier-to-noise ratio for a single channel of the photoreceiver is calculated to be more than 100 dB-Hz for the high case. The off-axis optical bench design is a potential candidate for China's future gravity missions.