Mission to Retrograde Geo-equatorial Orbit (RGEO) using lunar swing-by

Retrograde High Earth Orbit (RHEO) Missions have been investigated for nuclear waste disposal, space debris observation and investigation of gravitomagnetic field. Satellite insertion into RGEO through conventional approach is very difficult owing to high-energy requirement and range safety constraints. Here, lunar gravity assist is explored to design a feasible space mission architecture for RGEO. To design a realistic RGEO mission, different launch and orbital trajectory options are explored. It is found out that it is preferable to target for RGEO from a Geosynchronous Transfer Orbit (GTO) rather than from a Retrograde Geo-equatorial Transfer Orbit (RGTO). Though Hohman transfer from GTO to RGEO results in a heavy payload loss, at the same time, it is also demonstrated that it is highly advantageous to reach RGEO from GTO through lunar swing-by. In an optimized mode of transfer, it is possible to change the Inclination of Earth Return Orbit to 180° (Boomerang Orbit) from a typical GTO inclination. The net velocity requirement for such transfer to RGEO from GTO through lunar swing-by is about 2.0 km/s, which is translated to about 90% of GSO payload.