A fast steering mirror with ultra-low geometric tilt-to-length coupling noise for space-borne gravitational wave detection

Abstract

The misalignment between the geometric center and rotation center in fast steering mirrors (FSMs) poses a challenge for space-borne gravitational wave detection, as it results in geometric tilt-to-length (TTL) coupling noise. To address this issue, we have proposed a FSM structure that exhibits ultra-low geometric TTL coupling noise. The geometric TTL coupling noise is analyzed and evaluated strictly considering the FSM non-ideal tilt of the plane and the center shift characteristic of cartwheel flexure hinges under a small rotational angle. Compared to traditional FSM designs, our new design offers superior noise suppression capabilities and is capable of meeting the stringent piston effect noise requirements of 0.2 pm / Hz in the frequency band of 10 − 4 Hz ∼ 1 Hz under ideal conditions.

Research on High-Stability Composite Control Methods for Telescope Pointing Systems under Multiple Disturbances

“…After optimizing the constellation configuration for stability, the TianQin constellation can control the breathing angle variation within a range of ±0.1 • during each three-month observation window [4]. However, the variation in the breathing angle remains significantly larger than the far-field beam width of the telescope (about 5 µrad) [5], leading to a misalignment of the lines of sight for the two spacecraft, and thereby affecting the normal detection of gravitational waves. Therefore, to ensure the detection of gravitational waves, the TianQin mission specifies a pointing stability requirement of 10 nrad/Hz 1/2 in the frequency range of 0.1 mHz to 1 Hz [6] and utilizes the pointing mechanism to actively compensate for the breathing angle variation.…”