Dimensional Stability Ground Test and in-Orbit Prediction of SiC Telescope Frame for Space Gravitational Wave Detection

Abstract

Telescope is the key element of space brone gravitational wave detector. Its dimensional stability is required to be better than 1 pm/Hz 1/2 at 0.1 mHz. And SiC is the current most likely material for manufacturing telescope with high dimensional stability. Therefore, a potential SiC telescope frame is designed and tested. In addition, in orbit dimensional stability is predicted by a numerical model. The ground dimensional stability of SiC frame is tested with a fiber-based interferometer, and the temperature change data are collected at the same time. The results of which show that when room temperature fluctuation frequency is greater than 10 mHz, the dimensional stability is about 300 pm/Hz 1/2 . A numerical model is established which is consistent with the measured data. The in-orbit dimensional stability is evaluated using the numerical model and the thermal environment of Taiji, whose numerical simulation results shows that when space temperature fluctuation frequency is about 0.1 mHz the dimensional stability would be 6.49 pm/Hz 1/2 .

Non-Magnetic Negative Coefficient of Thermal Expansion Support Structure between Payloads in the Taiji Space Gravitational Wave Detection Satellite

“…Approximately 4% of this beam (i.e., 96% × 4% = 3.84% of the laser) is again reflected by the connector surface and will finally be reflected by the mirrors to focus on the fiber core to form the measurement beam (E m ). The beams E r and E m are described by the following equations, Equations ( 8) and ( 9) [12,22].…”

“…A r and A m are the amplitude factors, Φ r and Φ m are the phase factors, and f r and f m are the frequency factors. The response of the detector to the interfering beam is described in (10), and O Dect is the quantity of the optical intensity detected by the detector [12]. Because the process is zero-difference interferometry, both beams have the same frequency, so f r = f m .…”

“…However, temperature variations (about ±0.1 K) in the space environment cause small deformations in the support structure, which in turn lead to small changes in the optical path. Because the gravitational wave signal is very weak, even very small variations in the optical path can overwhelm the measurement signal [12]. In order to achieve the goal of the Taiji Program, i.e., an interstellar ranging accuracy of 5-8 pm/Hz 1/2 [12,13], it is necessary that "the support system between the payloads has a thermal stability on the order of pm to ensure the stability of the measured optical path".…”

“…Because the gravitational wave signal is very weak, even very small variations in the optical path can overwhelm the measurement signal [12]. In order to achieve the goal of the Taiji Program, i.e., an interstellar ranging accuracy of 5-8 pm/Hz 1/2 [12,13], it is necessary that "the support system between the payloads has a thermal stability on the order of pm to ensure the stability of the measured optical path". However, the internal support structure of the Taiji Program is different from the traditional optical support structure.…”