| ICESat is a NASA sponsored laser altimetry mission to be launched in December of 2001. ICESat will use the Geoscience Laser Altimetry System (GLAS) to measure the icesheets over Antarctica and Greenland. To perform this science mission, it is required that the actual ground track of the satellite be maintained within ±800 meters of a reference ground track that repeats every 183 days. It was shown that the tangential maneuvers required to maintain the ground track at the equator can be calculated with either longitude targeting or time targeting. Maintaining the ground track at the high latitudes required the development of a targeting scheme to calculate the required out-of-plane maneuvers. Two candidate targeting schemes, latitude targeting and improved latitude targeting, were developed. An optimization of the out-of-plane maneuvers, using the downhill simplex method, showed that improved latitude targeting is both an effective and efficient scheme for calculating out-of-plane maneuvers. Longitude targeting and improved latitude targeting were combined in a maneuver strategy used to simulate the 5 year mission of ICESat. This simulation showed that the ICESat ground track could be effectively maintained for 5 years. |
