Testing the predictions of galaxy formation scenarios on mildly- and non-linear regimes requires the detection from space of ultra-low surface brightness features both around galaxies (dwarf satellites) and in the cosmic web (filaments). The requirements of such a space mission imply innovative concepts for fast, wide-field, distortion-free telescopes. Several optical designs, based on freeform mirrors, are presented and compared here to address these stringent constraints on space-borne, wide field drift-scanning imaging. An optimal solution is presented, showing that a telescope with <i>f</i>/2, 4° × 2° FoV, with a 50 cm pupil can achieve the required exquisite image quality, free of distortion, with an optimal SNR in the detection of ultra-low surface brightness.
We present the conception of an anamorphic and telecentric scale changer with no distortion, able to provide magnifications in the range of 2 to 30 without any interchangeable optics, dedicated to ground or space applications. Several optical designs are investigated and the final configuration is based on off-axis five mirrors system with no moving elements. Four active mirrors are adapted to four different zoom configurations. A specific mechanical profile with variable thickness distribution is simulated and optimized on each mirror to allow using a minimal number of actuators. An opto-mechanical design will be presented, showing the implementation of actuators on the system. This work is done in the frame of the ANR project OASIX and will produce a lab prototype in 2015.