Optimization of transfer schemes between passive space objects in GEO vicinity

The paper compares two variants of re-orbiting space debris objects from the geosynchronous (GEO) region. Under the first re-orbiting variant, a spacecraft-collector (SC-collector) transfers between target objects (87 upper stages). A re-orbiting of the next in line object into a disposal orbit (DO) is carried out using special kits (thruster de-orbiting kits, TDK) which are placed on space debris objects by the SC-collector. Under the second variant, the object is pushed to a DO by the SC-collector itself, which then moves to a new space debris object from the DO of the previous object. It is shown that due to slow evolution of the orbital parameters in the GEO region, the same transfer schemes can be used for both re-orbiting variants. We describe geometrical peculiarities of relative positions of orbits in the near-equatorial region and consider two transfer schemes between objects. Under the first scheme, a transfer is executed when the orbits have the same inclination near the equator, and under the second scheme, when the orbit of the next object has the smallest inclination. Calculations show that both schemes are practically equivalent in terms of the averaged specific losses of the summary characteristic velocity (SCV) for a transfer (between two objects) and the duration - however, not all objects under consideration can be covered under the first scheme (when transfers are executed at times of equal inclinations). Hence, priority should be given to the scheme when the transfers are executed when the orbital inclination of the next object attains its smallest value. Based on the results of calculations, a conclusion can be made that 6 SC-collectors are required to clean the GEO protected region from spent upper stages. The active service life of each active SC is expected to be at most 8 years and its required SCV budget is at most 0.7 km/sec. A re-orbiting of one object to a DO requires on the average 10 m/sec; the return to a new object from the DO of the previous objects is energetically nearly equal to a sequential transfer between them. In this regard, as distinct from low orbits (in which it is preferable to use TDKs), it is more beneficial to follow the second variant for re-orbiting space debris objects from the GEO region (i.e., using the SC-collector itself). Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved.