Design and Performance Characterization of a Multi-Sensor Instrument for Stellar–Limb Optical Navigation

Stellar–Limb Optical Navigation (SL-OpNav) is a recently proposed technique for determining spacecraft absolute position at low altitudes, where classical horizon-based methods become unfeasible. The method estimates the observer position from elevation angles of cataloged stars above the planetary limb, but prior work did not establish the instrument design requirements needed for practical implementation. This paper presents the first systematic investigation of field of view, focal length, pixel scale, and SWIR optical constraints for a dedicated SL-OpNav payload, motivated by forthcoming short-wavelength infrared missions at the University of Leicester. Monte Carlo simulations under randomized attitude and limb-visibility conditions identify limb coverage, elevation-angle uncertainty, and lost-in-space recoverability as the dominant performance drivers. Sub-kilometer accuracy (position error < 1 km) is achievable when limb coverage exceeds 40–50% and elevation-angle errors remain below 0.5 pixels, while operational robustness requires lost-in-space recoverability above 80%. A four-sensor architecture satisfying these requirements is examined, employing a SWIR sensor with 15 μm pixels, a 20 mm focal length lens, and a 1280×1024 format to provide a short-axis field of view of 45 degrees per sensor. This design meets the accuracy and recoverability thresholds and establishes a practical basis for compact, GNSS-independent navigation instruments for low-altitude spacecraft operations.