Constellation and "Graveyard" Collision Risk for Several MEO Disposal Strategies

A comparison study of three satellite disposal strategies for medium Earth orbit constellations was performed. The study modeled long-term eccentricity growth of the disposal populations. The comparison metrics included collision risk between accumulating disposed satellites (the "graveyard" collision risk), collision risk posed by disposed satellites to operational constellation satellites, and close approaches posed by disposed satellites to operational satellites. The study included the GPS and COMPASS constellations. Results showed that a disposal strategy with initial high initial eccentricity (0.011 to 0.014) and average eccentricity growth significantly reduces global collision risk for GPS and COMPASS combined compared to a strategy that minimizes initial eccentricity.