Doppler effect in TianQin time-delay interferometry 后印本

摘要: The current design of space-based gravitational wave detectors utilizes heterodyne laser interferometry in inter-satellite science measurements. Frequency variations of the heterodyne beatnotes are predominantly caused by the Doppler effect from relative satellite motion along lines of sight. Generally considered to be outside the measurement band, the Doppler effect appears to have been largely overlooked in literature on numerical simulations of time-delay interferometry (TDI). However, the potential impact on the effectiveness of TDI should be assessed. The issue is particularly relevant to TianQin that features geocentric orbits, because of strong gravity disturbances from the Earth-Moon system at $<1\times 10^{-4}$ Hz. In this paper, based on high-precision orbital data obtained from detailed gravity field modeling, we incorporate the Doppler shift in the generation of TianQin's beatnote phase signals. To remove the large-scale Doppler phase drift at $<1\times 10^{-4}$ Hz, we develop a high-performance high-pass filter and consider two possible processing sequences, i.e., applying the filter before or after TDI combinations. Our simulation results favor the former and demonstrate successful removal of the low-frequency gravity disturbances for TianQin without degrading the TDI performance, assuming 10 m pseudo-ranging uncertainty. The filtering scheme can be used in developing the initial noise-reduction pipeline for TianQin.