Full scale active telescope engineering model

Abstract

Thales Alenia Space has designed and developed space high performance observation instruments for more than 40 years. The future missions will have to deal with better performance, better optical quality while from affordability point of view, the total mass, the development schedule and the final cost have to be reduced. These constraints induce an innovative generation of solutions based on larger entrance optics associated to high lightweight ratio. In these conditions, the enhancement of the final performance can only be guaranteed by using active optics in flight. In this context, Thales Alenia Space has been selected by French National Space Agency (CNES) to develop an active optics full scale telescope to path the way for the new class of Extremely high resolution telescopes. The whole building blocks have been already tested and qualified over the last 4 years. So, a deformable mirror is implemented in the future large telescopes in order to correct manufacturing residues, ground/flight evolution including gravity. Moreover, low mass and high agility satellites require more compact designs which implies telescope solutions more sensitive to misalignments. An active positioning mechanism is then also needed in order to correct the telescope alignment during flight conditions. A wavefront sensor is implemented in the mission focal plane and the global active loop validated. This paper presents the validation of active optic telescope on a full scale Engineering Model of 1500mm of entrance pupil diameter. All the active optic building blocks already qualified are mounted on this demonstrator. This Engineering model has followed a complete integration and alignment process that confirms the breakthrough simplification expected. The test plan validates on a full scale model the wave-front correction algorithms on-ground and in flight conditions, ensuring the best performance achievable with the telescope all along the lifetime.