Effect of Earth-Moon’s gravity on TianQin’s range acceleration noise. II. Impact of orbit selection

Abstract

The paper is a sequel to our previous work (Zhang et al. Phys. Rev. D 103, 062001 (2021)). For proposed geocentric space-based gravitational wave detectors such as TianQin, gLISA, and GADFLI, the gravity-field disturbances, i.e., the so called "orbital noise", from the Earth-Moon system on the sensitive intersatellite laser interferometric measurements should be carefully evaluated and taken into account in the concept studies. Based on TianQin, we investigate how the effect, in terms of frequency spectra, varies with different choices of orbital orientations and radii through singlevariable studies, and present the corresponding roll-off frequencies that may set the lower bounds of the targeted detection bands. The results, including the special cases of geostationary orbits (gLISA/GADFLI) and repeat orbits, can provide a useful input to orbit and constellation design for future geocentric missions.

Effect of Earth-Moon’s gravity on TianQin’s range acceleration noise. III. An analytical model

“…The results are shown in Fig. 3-5, all of which show good agreement and are consistent with [6]. Additionally, we have also tested the cases of 60 • and 120 • .…”

“…Especially, we have verified that the ASD curves obtained from the analytical model matches those from the numerical simulation. The work helps to confirm the numerical result of [5] and to better understand the underlying mechanism in terms of the frequency composition, as well as the dependence on orbit selection [6]. Particularly, we have also extended the model to capture the time-variable gravity from the Earth's free oscillations, which enters TianQin's measurement band.…”

“…Hence, through a Fourier-style decomposition in terms of frequency components, the formula can reveal the frequency-domain characteristics of the effect of the Earth's gravity field { Cnm , Snm } on the intersatellite range-acceleration ρ. Moreover, the dependence on the orbit elements a, i, Ω also allows one to study the impact of orbit selection [6]. To see explicit examples of Eq.…”

“…First we discuss the case of TianQin's orbit and compare the resulting ASD curves. Then we alter the orbital elements to different values [6] so as to test the model in more generic settings.…”

“…According to the estimates, we expect the effect of the Earth-Moon's gravity to be below the noise * zhangxf38@sysu.edu.cn requirement in the sensitive frequency band of TianQin (10 −4 − 1 Hz) and hence not constituting a showstopper to the mission [5]. Furthermore, we also explored how the Earth-Moon's gravity disturbance varies with different orbital radii and orientations for TianQin [6]. A general trend is that the disturbance shifts to lower frequencies as the orbital radius increases, which may set the lower bound of the measurement band.…”