APOGEE MANEUVER STRATEGIES FOR THE INMARSAT-2 SPACECRAFT

The INMARSAT-2 spacecraft are built by British Aerospace, based on the Satcom International EUROSTAR 1000 bus. The main features of the plat form are: spin stabilization during the transfer phase; a 490 N thrust bipropellant apogee motor, allowing the use of multiple burn strategi es to achieve injection into geosynchronous orbit; and compatibility f or launch on Ariane 4 and Delta II. The main characteristics of the IN MARSAT-2 mission are: an inclined drift orbit (up to 2.7 degrees) is t argeted at the end of the last Apogee Engine Firing (AEF), in order to extend the lifetime of the spacecraft; and in case of a Delta II tran sfer orbit, an apogee bias has been chosen to counteract the effects o f the launcher dispersions upon apogee radius, and four different argu ments of perigee have been selected to facilitate the node line rotati on necessary for an Inclined Orbit Mission (IOM). This paper presents the results of the different methods of calculation of orbital correct ions which have been used for mission analysis and operations.