Debris-Cloud Collision Risk Assessment with GSOC Collision Avoidance System

Abstract

After an in-orbit break-up event, tracking and cataloging fragments takes time, leading to a blackout period where debris is not yet cataloged, and Conjunction Data Messages (CDMs) cannot be issued. Traditional 1-vs-1 collision assessments are ineffective in the short-term phase of debris cloud evolution, which typically lasts some hours after the fragmentation. Additionally, untracked small fragments further increase the risk of undetected impacts on operational spacecraft. In this context, the Flight Dynamics (FD) team at the German Space Operations Center (GSOC) is developing a tool to evaluate the potential collision risk posed by a fragmentation event to their assets, further enhancing the capabilities of their already established Collision Avoidance System (CAS). The proposed methodology is based on a mapping technique that links the position evolution of a primary spacecraft to the Initial Spread Velocity Space (ISVS) at breakup time by recursively solving a series of multi-revolution Lambert’s problems. The Probability of Collision (PoC) is then calculated by integrating the Probability Density Function (PDF) of the ejection velocities, as defined by NASA’s Standard Break-up Model (SBM), over the volume swept by the primary image in the ISVS. The tool is tested using a benchmark scenario from the literature, with the PoC of a single fragment validated against a Monte Carlo simulation. Specifically, the resulting cumulative risk metric is compared to the one obtained by sampling from the same ejection velocity distribution defined by the SBM and recording any collisions that occur for each sample.