Comparison of Orbital Parameters for GEO Debris Predicted by LEGEND and Observed by MODEST: Can Sources of Orbital Debris be Identified?

Since 2002, the National Aeronautics and Space Administration (NASA) has carried out an optical survey of the debris environment in the geosynchronous Earth-orbit (GEO) region with the Michigan Orbital Debris Survey Telescope (MODEST) in Chile. Under gravitational perturbations the distributions of uncontrolled objects, both Correlated (CTs) and Uncorrelated (UCTs) targets, in GEO orbits will evolve in predictable patterns, particularly evident in their inclination and right ascension of the ascending node (RAAN) distributions. There are several clusters ((1) have used a "cloud" nomenclature) in observed distributions that show evolution from year to year in their inclination and ascending node elements. Identification of the source(s) for these "clusters of UCTs" would be advantageous to the overall definition of the GEO orbital debris environment. This paper will present arguments for the identity of the source of the "clustering of UCTs" roughly centered on an inclination of 12° and a RAAN of 345°. The breakup of the Titan 3C-4 transtage on February 21, 1992 has been modeled using NASA's LEGEND (LEO-to-GEO Environment Debris) code to generate a GEO debris cloud. Breakup fragments are created based on the NASA Standard Breakup Model (including fragment size, area-to-mass (A/M), and delta-V distributions). Once fragments are created, they are propagated forward in time with a subroutine GEOPROP (GEO Propagator). Perturbations included in GEOPROP are those due to solar/lunar gravity, radiation pressure, and major geopotential terms.