Second generation Indian national satellite system space segment — INSAT II

Abstract

The Indian National Satellite System (INSAT) for Communications, Broadcasting and TV distribution, Radio networking and Meteorological earth observations and data relay, is now operational with the first generation INSAT-I Spacecraft manufactured abroad. These will be replaced by second generation INSAT-II Spacecraft designed, built in India and eventually launched from India. To meet the INSAT-II mission requirements in a cost effective manner, the chosen configuration consists of two spacecraft collocated at the primary location and additional spacecraft at other (major path) locations. The collocated spacecraft are identical except for their FSS payloads operating on mutually orthogonal polarisations. Thus, together they double the FSS capability at this location simulating a large “virtual” satellite. This large capacity enables network connectivities to be made with relatively small spacecraft. The advantages of this concept, such as avoidance of a large, mostly idle spare spacecraft, compatibility with the projected capacity of the Indian Geosynchronous Launch Vehicle, GSLV, graceful degradation of system capacity in the event of one catastrophic failure, capability to match system growth to capacity build-up, etc. are explained. The individual multipurpose spacecraft which comprise this space segment are described. The technical and operational problems involved in positioning and operating the collocated spacecraft so as to derive the advantages of an equivalent large virtual satellite, while at the same time, reducing the probability of collision/obscuration to acceptably low values and minimising operational complexities are also discussed in this paper.