GSat 4 (HealthSat)

GSat 4 [ISRO]

GSAT-4 is envisaged as a technology demonstrator. The communication payload consists of multi-beam Ka-band bent pipe and regenerative transponder and a navigation payload in C-band, L1 and L5 bands (GAGAN). GSAT-4 employs several new technologies like bus management unit, miniaturised dynamically tuned gyros, lithium-ion battery, 70 Volt bus for Ka-band TWTAs and electric propulsion. GSAT-4 also incorporates technological experiments like on-board structural dynamic experiment, thermal control coating experiment and vibration beam accelerometer. With a lift-off mass of about 2180 kg, the spacecraft generates 276 W of power in summer solstice.

Originally it was to feature a piggyback astronomical payload, the Israeli TAUVEX-2 (Tel Aviv University Ultra Violet Explorer), which was in turn originally slated to fly on the Spektr-RG spacecraft. TAUVEX was to be mounted on a rotating table on the east surface of GSat 4. It was to be operated in a scanning mode. The TAUVEX-II payload comprising three Ultra-Violet band telescopes was developed by Tel Aviv University and Israel space agency, ELOP, for surveying a large part of the sky in the 1400-3200 Å wavelength. Due to mass constraints, TAUVEX was removed from GSat 4 shortly before launch. In February 2011, TAUVEX was finally cancelled.