GSAT-8 (INSAT-4G), India’s advanced communication satellite and constructed by ISRO, is a high-power communication satellite being inducted in the INSAT system. Weighing about 3,100kgs at lift-off, the satellite was the first that was configured to carry 24 high power transponders in Ku-band and a two-channel GPS Aided Geo Augmented Navigation (GAGAN) payload operating in L1 and L5 bands. Later identical satellites like GSAT-10 and in-orbit spare GSAT-15 would follow.

The 24 Ku band transponders will augment the capacity in the INSAT system. The GAGAN payload provides the Satellite Based Augmentation System (SBAS), through which the accuracy of the positioning information obtained from the GPS Satellite is improved by a network of ground-based receivers and made available to the users in the country through the geostationary satellites.

Prior to launch, the spacecraft was transported from India to Cayenne – Rochambeau Airport in French Guiana by an Antonov An-124 cargo aircraft. The success of the launch is said to have made up for the previous loss of two satellites on the indigenous GSLV rocket operated by ISRO. GSAT-8 was co-located with INSAT-3E at 55°E.

GSAT-8 was successfully launched on May 21^st, 2011, in a dual launch with ST-2 for satellite operator SingTel from Singapore on an Ariane 5ECA rocket booster, operated by launch operator Arianespace from the Kourou Space Port in French Guyana.