Environmental effect of space debris repositioning

One of the proposed measures to limit the number of near-Earth orbiting fragments to a sustainable level is to actively remove large derelict objects from crowded orbital regions. The two main removal procedures considered so far are (1) a direct targeted reentry maneuver or (2) a deorbit maneuver resulting in a predicted 25-year lifetime for the target object. We study here the viability of a third option, which consists of repositioning the target to an optimally chosen altitude according to a selected benefit/cost objective function. The objective function accounts for both the maneuver cost and the reduction of environmental criticality of the object. Numerical simulations are conducted to determine the optimal sequence of repositioning maneuvers for a given available deorbiting propellant. Results show that an optimal repositioning campaign tends to displace ton-class objects from around 900-1000 km altitude down to around 750-800 km altitude and to redistribute debris mass from altitudes around 1500 km across lower density nearby altitudes. Comparisons with a 25-year lifetime deorbiting suggest a significant performance improvement.