Off-Axis Three Mirror Anastigmat with an Integrated Primary and Tertiary Mirror

Abstract

Space telescopes are indispensable tools for scientific missions. They offer unique insights into Earth-oriented studies and astronomical observations by measuring phenomena which are not always visible from the ground. Among telescope configurations, the three mirror anastigmat (TMA) is a commonlyutilized system due to its excellent ability to control aberrations over large field of views. While off-axis TMA systems remove the central obstruction, they often introduce challenges regarding opto-mechanical alignment, particularly with active, on-orbit systems. This thesis aims to address these challenges by discussing the development of the Monolithic Off-axis Three-mirror System (MOTS), whose primary and tertiary mirrors are formed with a single substrate. With a focal length of 2480 mm at f /6, the MOTS telescope demonstrates a diffraction-limited performance across its 1.2◦ x 0.5◦ field of view, with excellentcontrast for resolving fine details. The system is designed for 12 micron pixels and maintains a flat, uniform image plane with minimal distortion (≤0.19%). The monolithic mirror serves as a single reference surface during optical alignment, reducing the complexity to a two rigid-body system, and providing a non-degenerate solution to active alignment of the secondary mirror. Preliminary stray light analysis demonstrates uniform illumination (≥94%) with sharp attenuation beyond the field of view. Overall, the MOTS telescope presents an alternate solution for advancing space-based imaging by addressing challenges often encountered with off-axis systems.