Gravitational influence of thermally induced sunshield deformation of TianQin satellites

Abstract

The TianQin mission aims to detect millihertz gravitational waves in high geocentric orbits using inter-satellite laser interferometric links and drag-free control. However, solar thermal noise in the detection band and significant variations in solar flux can affect the residual acceleration noise of the free-falling test masses through the gravitational force from the satellite itself. In this paper, we focus on studying the sunshield assembly of the TianQin satellite, which includes a solar insulating combination of the sunshield and the satellite’s top plate. We employ an integrated simulation that combines thermal, electrical, structural, and gravitational analyses to show how solar-induced thermal expansion of the sunshield affects the self-gravity on the test masses during TianQin’s 3-month observation windows. Our findings indicate that thermal deformation of the sunshield ranges from 2.0 to 5.3 mm. The results show that the static self-gravity induced accelerations from the sunshield assembly along the sensitive axis of the TM under both cold and hot cases are approximately $8.7\times 10^{-11}\text{m/s}{}^2$. Additionally, solar-induced thermal noise in the sunshield assembly contributes to a self-gravity fluctuation of about $3.9\times 10^{-16}\text{m/s}{}^2/{\text{Hz}}^{1/2}$ at 1 mHz, which satisfies the self-gravity requirements. These results provide useful references for future research on the self-gravity effect and strategies for self-gravity mitigation in similar projects.