Optimal transfer schemes between space debris objects in geostationary orbit

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 transfers between target objects (87 upper stages). Each object is re-orbited into a disposal orbit (DO) using special thruster de/re-orbiting kits (TDK) which are placed on space debris objects by the collector. Under the second variant, the object is pushed to a DO by the collector itself, which then moves to a new space debris object from the previous object's DO. It is shown that due to the slow evolution of the orbital parameters in the GEO region, the same transfer schemes can be used for both re-orbiting variants. We describe 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 both the averaged ΔV for a transfer and the duration — however, not all objects under consideration can be covered under the first scheme. Hence, priority should be given to the second scheme. It can be calculated, that 6 collectors are required to clean the GEO protected region from spent upper stages. The service of each is expected to be at most 8 years and its required ΔV budget is at most 0.7 km/s. A re-orbiting of one object to a DO requires on average only 10 m/s; the return to a new object from the DO of the previous object is nearly energetically equal to a sequential transfer between the objects. 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 collector itself). © 2020 IAA