Abstract:
                        
                        Estimates of collision, warning, and maneuver rates are of high interest to spacecraft operators in all orbital regimes, especially in the Low Earth Orbit (LEO) regime where encounters are an ever-increasing occurrence.  These rates are also of great importance and interest to the global space community, including space policymakers, national regulators, mission designers, and spacecraft designers.  The fuel expended to avoid such encounters has a direct and material influence on the maneuver capabilities, flight operations team resource loading, and SSA quality required to safely operate in space.
In this paper, we update our previous encounter and collision rate estimates for the current resident space object catalog.  New for this update, estimated collision rates also incorporate planned and/or hypothetical (New Space) large constellations based on a multitude of license filings and applications.  Collision estimates are further refined based on estimated object sizes to better represent collision risk with the satellite population.  The current public space catalog is additionally augmented by a MASTER model-based representative catalogue of small debris too small to currently track, but which may soon be tracked and maintained by new SSA sensors and systems.  
We also consider the elements of information which may be relevant to assembling a useful metric for evaluating a constellation’s collision fragmentation potential.  As a demonstration, a sample metric is adopted and applied to the entire set of proposed large constellations having a current license application to facilitate a comparative assessment and rank ordering of the impact of each proposed large constellation.  These results indicate that collision risk in LEO is fairly high when examined in the context of a satellite constellation’s lifetime.
                        
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                                Alfano, S., Oltrogge, D.L., and Shepperd, R., “LEO constellation encounter and collision rate estimation:  An update,” 2nd IAA Conference on Space Situational Awareness, IAA-ICSSA-20-0021, 14 January 2020, accessible at https://comspoc.com/Resources/Content/Private/C-20220423T092204/Paper/20200122_LEO_Encounter_and_Collision_Rate_Updates_Alfano_Oltrogge_Final.pdf.