Space debris mitigation in geosynchronous orbit

In order to preserve the geosynchronous region, the Inter-Agency Space Debris Coordination Committee (IADC) proposed and endorsed a re-orbiting strategy for spacecraft at the end-of-life: they should be disposed above the synchronous altitude and passivated, to reduce the risk of inadvertent explosions. The recommended perigee altitude of the disposal orbit took into account all relevant perturbations and was a function of the expected perturbing acceleration induced by solar radiation pressure. It was intended to prevent any further interference with a properly defined geostationary protected region. This paper addresses four main aspects related to space debris mitigation in geosynchronous orbit, by reviewing the rationale and expected effectiveness of spacecraft end-of-life disposal. First, the role played by the initial eccentricity vector on the trajectory evolution of disposed satellites. Second, the collision risk posed by debris clouds and the importance of passivation to prevent energetic breakups. Third, the impact of the operational limitations characteristic of aging spacecraft (e.g. reliability of residual propellant estimates, maneuver constraints and subsystems performance) on the definition of practicable disposal strategies. Last, the potential problem represented by low energy, non-explosive, fragmentations leading to the release of debris with high area-to-mass ratio. Based on the modeling results obtained, some possible mitigation solutions are discussed, including possible enhancements or revisions of the IADC recommendation.