Trajectory analysis for the lunar flyby rescue of AsiaSat-3/HGS-1

On May 13, 1998, the Hughes Global Services 1 Spacecraft (HGS-1, originally known as AsiaSat 3) became the first commercial spacecraft to fly by the Moon on a trajectory to reposition it into a useful geosynchronous orbit. This was necessary due to the failure of the last stage of the launch vehicle that left it in a high inclination, eccentric, and unusable orbit. The spacecraft did not have enough propellant to perform the maneuvers required to place it into its intended geostationary orbit via a standard transfer trajectory. However, it did have enough propellant to place it on a trajectory that flew by the Moon twice to finally achieve a useful low inclination geosynchronous orbit. In addition to being the first commercial operation in the vicinity of the Moon, it was the last successful lunar mission of the twentieth century. We discuss of the events leading up to the start of the rescue operation that included contributions from external organizations. We also describe the analytic estimates used to construct the trajectory and provide an overview of the details of the actual mission.