Design of a wide-temperature-range star camera and analysis of thermally induced aberrations and stray light

As a critical component for spacecraft attitude measurement, inertial reference establishment, and rendezvous and docking missions, the stringent requirement for sub-arcsecond-level pointing accuracy in star cameras demands a compact optical mechanism and an opto-mechanical-thermal (OMT) integrated design. This paper presents a star camera based on a coaxial quad-reflector optical configuration. The primary and tertiary mirrors share a common substrate, achieving an effective aperture of 64 mm and a focal length of 195 mm. The four aspheric mirrors provide a ±2.5° field of view with an objective numerical aperture of 0.26. The system exhibits outstanding optical performance, with an MTF exceeding 0.7@40 lp/mm, approaching the diffraction limit. 80% encircled energy diameter ≤ 11 μm, absolute distortion not exceeding 0.1%. The system employs Zerodur^® glass ceramics and 4J32 Invar alloy, which coupled with a flangeless primary mirror and a compact 50 mm axial layout, ensure excellent thermal insensitivity. Coupled finite element analysis, using 36 Zernike polynomials, shows that within a temperature range of −40°C~60°C, the root mean square (RMS) surface error of the primary mirror remains below 6.19 nm. Rigid-body displacement is maintained within ±0.5 μm/10 K, MTF degradation remains below 20%, and the fluctuation of the 80% encircled energy diameter is less than 5 μm. Stray light suppression is achieved using a lightweight baffle ring with a multi-stage extinction cone. The extended baffle yields a Point source transmittance of 3×10⁻⁹ at 30° off-axis, improving stray light suppression by two orders of magnitude and enabling detection of faint 10th-magnitude stars. Thermal vacuum testing validated the system's performance, demonstrating a centroid positioning repeatability of 0.08 pixels and providing a valuable reference for the design of high-precision space optical payloads.