Top level systems requirements analysis for a ground cooperative orbital debris avoidance system

The increasing population of orbital debris in low earth orbit establishes an environment in which the risk of damage or destruction to strategic space assets is no longer insignificant. Using NASAs ORDEM2000 software as a guide, risk of a 5m
²
satellite in 800km sun synchronous orbit being hit by a 5mm particle is now close to 1% per year. The continuing execution of operations in low earth orbit will increasingly rely on a combination of risk reduction activities such as planned end-of-life deorbit, elimination of separable deployments and collision avoidance maneuvering. This paper explores the viability of an onboard detection and maneuvering system which uses ground derived debris ephemeris to cue an onboard active sensor during possible collision scenarios to detect an imminent collision. Conjunction analysis is already provided to existing satellites, but with that knowledge, an onboard sensor can be used to supplement the ground information by searching along the accurately known approach vector, effectively eliminating the need for wide angle search. With such a system, scans are simplified, and duty cycles are limited only to a couple of seconds during the actual conjunctions. Analysis shows that even though uncertainty in debris position can exceed 10km, the approach vector for potential collisions can be established with sub-milliradian precision. Analysis is executed for a sample spacecraft in sun-synchronous orbit to establish sensor requirements for field of regard, range, sample rate and angular search volume. Photometric analysis establishes baseline parameters for a candidate system and the requirements for a propulsive based evasion system are explored.