An inflatable circular membrane mirror for space telescopes

The performance of ground telescopes is limited by atmospheric distortion. Nowadays all large ground telescopes adopt adaptive optics for overcoming this limitation. Sending space telescopes outside the troublesome atmosphere might be a natural solution to overcome the atmospheric distortion. However, the cost of development and launch, and the size of launch fairing severally limit this option. Inflatable optics is major candidate for overcoming these technical and budget limits. In this study, we performed thickness optimizations of a membrane mirror for the mirror to be parabolic. Our optimization showed that this optimized mirror is still not good enough for visible observation. However, with limiting the effective optical surface area, the mirror was demonstrated to be used as a primary mirror in infrared bands. In addition, the wavefront errors are also shown to main contributors: piston, defocus and spherical aberrations. Adapting an adaptive secondary mirror with 19 actuators, which has been developed for ground telescopes, could remove the major wavefront errors. Therefore, combining an inflatable primary mirror and an adaptive secondary mirror can be a candidate for future large space telescopes.