Space-based sensor fusion for refined space debris cataloguing

Abstract

Monitoring centimetre-class orbital debris is critical for spacecraft safety and the long-term sustainability of Low Earth Orbit (LEO), as fragments below current ground-based tracking thresholds can still cause mission-ending damage. This study presents the payload-level design of a dual-sensor architecture for space-based space situational awareness (SBSSA), comprising an active radar for Initial Orbit Determination (IOD) and a visible-band optical sensor for Precise Orbit Determination (POD). For each payload, a metrics-driven trade space is developed that maps design variables to catalogue-relevant figures of merit. The optical analysis prioritises time-on-detector (dwell), angular accuracy, field of view (FOV), and illumination geometry; the radar analysis focuses on volumetric coverage, range and range-rate precision, dwell, and off-nadir viewing. Operational constraints from power, pointing, and communications are incorporated. Observation concepts are defined accordingly: the optical payload is considered in sun-synchronous orbit with anti-sun pointing to ensure favourable illumination and background conditions, while the radar payload employs off-nadir scanning to enlarge coverage within the 600–800 km debris band. Minimum detectability conditions are set to reflect catalogue integration requirements. Representative Pareto-optimal designs are identified for both payloads and assessed against higher-level indicators, including catalogue maintenance potential, observation scheduling feasibility, and downlink load. The outcome yields concrete recommendations on optical aperture, detector format, FOV, and integration times, together with radar effective range, FOV geometry, and measurement precision. The translation from payload parameters to constellation-level implications—revisit frequency, handover latency, and the minimum number of spacecraft needed to sustain POD cadence—is quantified. A simplified joint simulation of the two payloads is included only to check consistency between subsystem design and system-level behaviour. While individual payload requirements are met, temporal handover between radar detections and optical follow-ups emerges as a limiting factor, motivating refinement of orbital geometry, sensor co-location, and scheduling strategies prior to constellation optimisation.