HYPATIA and STOIC: an active optics system for a large space telescope

The next generation of UVOIR space telescopes will be required to provide excellent wavefront control despite perturbations due to thermal changes, gravity release and vibrations. The STOIC project is a response to an ESA Invitation to Tender to develop an active optics correction chain for future space telescopes. The baseline space telescope being considered is a two-mirror, 4m telescope with a monolithic primary mirror – we refer to this concept as Hypatia. The primary mirror diameter could be extended, but is limited in the near future by launch vehicle dimensions. A deformable mirror (pupil diameter 110mm) will be an integral part of the telescope design; it is being designed for high precision and the ability to maintain a stable form over long periods of time. The secondary mirror of the telescope will be activated to control tip-tilt, defocus and alignment with the primary. Wavefront sensing will be based on phase diversity and a dedicated Shack-Hartmann wavefront sensor. The project will develop a laboratory prototype to demonstrate key aspects of the active correction chain. We present the current state of the preliminary design for both the Hypatia space telescope and the laboratory breadboard.