Membrane Space Telescope: Active Surface Control with Radiative Adaptive Optics

TL;DR

This paper introduces a novel radiative adaptive optics system for membrane space telescopes, enabling precise shape control of ultra-lightweight mirrors through thermal radiative coupling, demonstrated with a prototype achieving ~15nm RMS accuracy.

Contribution

It presents the modeling and experimental validation of radiative shape control for membrane mirrors, a new approach for lightweight space telescope optics.

Findings

Achieved ~15nm RMS surface figure control in experiments.

Developed detailed influence function modeling for radiative shaping.

Demonstrated closed-loop control with wavefront sensor.

Abstract

Sensitivity and resolution of space telescopes are directly related to the size of the primary mirror. Enabling such future extremely large space telescopes or even arrays of those will require to drastically reduce the areal weight of the mirror system. Utilizing a thin parabolic polymeric membrane as primary mirror offers the prospect of very low weight and the flexible nature of those membranes allows compactly store them upon launch. Upon deployment the structure is unfolded and the mirror shape restored. Being an extremely thin structure, an active shape correction is required. Utilizing a thermal control of the surface via radiative coupling, localized shape changes are imprinted into the membrane telescope. In this paper we present the modelling and experimental test of the radiative adaptive optics. A detailed modeling of the influence function of the radiative shaping onto the membrane mirror has been carried out. Experimentally we have been radiatively actuated the shape of a prototype mirror in closed loop with a wavefront sensor and proven that we can control the mirrors surface figure to a ~15nm RMS precision.