Design and Modelling of a Compact Dual-Purpose Star Tracker and Debris Detector for Small Satellites: Straylight, Thermal, and Structural

In this paper the design, modelling, and performance assessment of a miniaturised dual-purpose optical instrument for small satellites are presented. The instrument can function as a star tracker and as a space-debris detection camera. The system integrates commercial off-the-shelf components, i.e., a CMOS sensor, a processing unit and lens assembly, together with a custom three-vane optical baffle optimised for stray-light suppression. A complete numerical evaluation was conducted through optical ray-tracing, lumped-parameter thermal modelling, and structural finite-element analysis to validate the instrument prior to hardware testing. Optical simulations confirmed effective stray-light suppression and acceptable Point Source Transmission behaviour, enabling signal-to-noise ratio performance suitable for star and debris detection up to ∼5.8 mag. The resulting instrument, with a mass of approximately 172 g and dimensions of 105 mm × 52 mm × 52 mm, demonstrates a compact, low-cost, and multifunctional solution for small-sized platforms. Future work includes environmental testing and on-orbit demonstration to prepare the system for flight qualification.