Long-term stability of the picometer-resolution interferometer on TianQin-1 satellite

As ground-based gravitational wave (GW) detection has opened a new window for exploring the Universe, space-based GW detection will be the next frontier to deepen the understanding of galaxy evolution and massive black holes merging. TianQin-1 is a technology verification satellite for the space-based GW detector TianQin. One of the key technologies demonstrated in TianQin-1 is a high-precision and ultra-stable interferometer, with a noise floor lower than 100 pm / Hz 1 / 2 @ 0.1 Hz . In this paper, we report the long-term stability of the interferometer in the TianQin-1 satellite, which contains a quasi-monolithic optical bench made through hydroxide catalysis bonding (HCB). According to the results of the ground and in-orbit tests, the long-term stability of the interferometer for 13 months after launch has been evaluated. The resolution of the interferometer is better than 30 pm. The noise level of the interferometer is about 30 pm / Hz 1 / 2 @ 0.1 Hz and 10 pm / Hz 1 / 2 above 1 Hz, fulfilling the mission requirement of TianQin-1. The successful in-orbit operation has demonstrated the interferometer’s high precision and long-term stability based on the quasi-monolithic optical bench.