Conjunction challenges of low-thrust geosynchronous debris removal maneuvers

•Conjunction likelihoods on low-thrust trajectories to GEO disposal orbit are evaluated.•Conjunction events rated via risk metric based on GEO-relative proximity and speed.•Average number of conjunction events rises hyperbolically as thrust level decreases.•Appropriately timing the start of the re-orbit maneuver mitigates conjunction likelihood.

The conjunction challenges of low-thrust engines for continuous thrust re-orbiting of geosynchronous (GEO) objects to super-synchronous disposal orbits are investigated, with applications to end-of-life mitigation and active debris removal (ADR) technologies. In particular, the low maneuverability of low-thrust systems renders collision avoidance a challenging task. This study investigates the number of conjunction events a low-thrust system could encounter with the current GEO debris population during a typical re-orbit to 300 km above the GEO ring. Sensitivities to thrust level and initial longitude and inclination are evaluated, and the impact of delaying the start time for a re-orbiting maneuver is assessed. Results demonstrate that the mean number of conjunctions increases hyperbolically as thrust level decreases, but timing the start of the maneuver appropriately can reduce the average conjunction rate when lower thrust levels are applied.