Indian National Satellite System (INSAT) is a series of multipurpose Geo-Stationary satellites launched by ISRO to satisfy the telecommunications, broadcasting, meteorology, and "search and rescue" needs of India. Commissioned in 1983, INSAT is the largest domestic communication system in the Asia-Pacific Region. Active satellites of this series include INSAT-2E, INSAT-3A, INSAT-3B, INSAT-3C, INSAT-3E, KALPANA-1 (METSAT), GSAT-2, EDUSAT (GSAT-3) and INSAT-4A.
INSAT satellites provide transponders (about 150) in various bands (C, S, Extended C and Ku) to serve the television and communication needs of India. Some of the satellites also have the Very High Resolution Radiometer (VHRR), CCD cameras for metrological imaging. The satellites also incorporate transponder(s) for receiving distress alert signals for search and rescue missions in the South Asian and Indian Ocean Region, as ISRO is a member of the Cospas-Sarsat programme.