Laboratory demonstration of a cryogenic deformable mirror for wavefront correction of space-borne infrared telescopes

TL;DR

This paper presents a cryogenic deformable mirror with 1,020 actuators, demonstrating its operation at cryogenic temperatures and its potential to improve wavefront correction in space-borne infrared telescopes.

Contribution

We developed and experimentally validated a MEMS-based cryogenic deformable mirror suitable for space telescopes, with high repeatability and no hysteresis, enabling effective wavefront correction.

Findings

Successful operation at 5 K to 295 K temperatures.

High repeatability of a few nm RMS in deformation.

Simulated PSF improvement with wavefront correction.

Abstract

This paper demonstrates a cryogenic deformable mirror (DM) with 1,020 actuators based on micro-electrical mechanical systems (MEMS) technology. Cryogenic space-borne infrared telescopes can experience a wavefront error due to a figure error of their mirror surface, which makes the imaging performance worse. For on-orbit wavefront correction as one solution, we developed a MEMS-processed electro-static DM with a special surrounding structure for use under the cryogenic temperature. We conducted a laboratory demonstration of its operation in three cooling cycles between 5 K and 295 K. Using a laser interferometer, we detected the deformation corresponding to the applied voltages under the cryogenic temperature for the first time. The relationship between voltages and displacements was qualitatively expressed by the quadratic function, which is assumed based on the principle of electro-static DMs. We also found that it had a high operating repeatability of a few nm RMS and no significant hysteresis. Using the measured values of repeatability, we simulated the improvement of PSF by wavefront correction with our DM. These results show that our developed DM is effective in improving imaging performance and PSF contrast of space-borne infrared telescopes.