Advanced inter-spacecraft offset frequency setting strategy for the Taiji program based on a two-stage optimization algorithm

Abstract

For space-based gravitational wave (GW) detection, the continuity of detection data acquisition is crucial to the inversion of wave sources and the realization of scientific goals. To control the inter-spacecraft beat-note frequency in an appropriate range for continuous gravitational wave detection and to reduce the upper bound of the beat-note frequency for improving the detection capability, a two-stage optimization algorithm is proposed to solve the offset frequency setting strategy in the Taiji program. The optimization objectives are the maximum offset frequency duration and minimum upper bound of the beat-note frequency. Considering all feasible phase-locked schemes, Doppler frequency shift, and the bandwidth of the phasemeter, a series of offset frequency setting strategies satisfying the conditions was obtained. The solution results show that the upper bound can be reduced to 16 MHz and, in this case, the offset frequency changes nine times with a minimum and maximum offset frequency duration of 90 days and 713 days, respectively. If the Doppler frequency shift is constrained, the minimum upper bound can be reduced to 14 MHz. When the minimum duration is increased, the minimum upper bound is increased. These results show that, by varying the offset frequency a limited number of times, the data continuity requirements of the Taiji program can be satisfied, and the phasemeter development difficulty and detection capability can be balanced, and may provide a reference for the phasemeter design, the setting of phase-locking schemes, and inter-spacecraft offset frequency in the Taiji program.