The Evolution of the Geostationary Platfom Concept

The paper will review the conceptual development over the last decade of the use of very large spacecraft, i.e., "platforms," in geostationary orbit. Geostationary platforms were originally conceived as an efficient means of increasing the capacity at a point in the geostationary orbital arc. This geostationary platform was seen as a solution to the predicted crowding of the orbital arc since it could provide the functions of many individual satellites of conventional design. Also, geostationary platforms have been suggested for mounting very large antennas as will be required for mobile communications, or high power sources as will be required for broadcast services to small terminals. More recently these "large satellite" platforms were also envisioned as including earth observation and other science payloads. The advent of the Space Station which can provide a staging base for platform assembly and test in space at low earth orbit (LEO), prior to launch to geostationary earth orbit (GEO), will introduce a new dimension to practical platform design. This dimension has reintroduced the geostationary platform concept as a potential communications and science spacecraft of the post-IOC-Space Station family. This paper describes the evolution of concepts for geostationary platforms over the last decade based on both communications and science user scenarios developed worldwide.