STMEdge: An Ultra-Low Latency, Zero-Allocation C++ Engine for Autonomous On-Board Conjunction Screening and Reactive Collision Avoidance

The exponential expansion of satellite mega-constellations and orbital debris in Low Earth Orbit increases the operational risk of catastrophic collisions. Traditional centralized, ground-based Space Situational Awareness architectures depend on heavy numerical infrastructure, human-in-the-loop validation, and continuous communications, introducing structural latency and leaving spacecraft vulnerable during ground-link blackouts or delayed tracking updates. To resolve this vulnerability, we present STMEdge, a high-performance, header-only, dependency-free C++ engine designed for real-time Conjunction Assessment Screening and emergency Collision Avoidance Maneuver sizing directly on spacecraft On-Board Computers. The software implements a deterministic pipeline consisting of a constant-work altitude filter, an epoch-normalized kinematic anti-tunneling sieve, a secular mean-element orbital propagator, an analytical golden section search for exact time-of-closest-approach refinement, a linearized state transition matrix accounting for atmospheric drag variability noise, a closed-form two-dimensional encounter plane collision probability evaluator, and a reactive impulsive in-track avoidance maneuver optimizer based on relative orbital dynamics. The system is engineered strictly as an on-board contingency triage engine for resource-constrained flight processors (such as ARM and RISC-V platforms on CubeSats and constellation buses). By eliminating dynamic heap allocations in the critical execution loop, STMEdge provides deterministic execution guarantees that allow autonomous spacecraft to continuously ingest local ephemeris catalogs, filter non-threatening encounters, assess collision risks, and compute emergency avoidance burns in communication-denied environments without ground intervention