PSLV versus GSLV
- PSLV is designed mainly to deliver the ―earth-observation or ―remote-sensing‖ satellites with lift-off mass of up to about 1750 Kg to Sun-Synchronous circular polar orbits of 600-900 Km altitude.
- PSLV is also used to launch the satellites of lower lift-off mass of up to about 1400 Kg to the elliptical Geosynchronous Transfer Orbit (GTO).
- PSLV is a four-staged launch vehicle with first and third stage using solid rocket motors and second and fourth stages using liquid rocket engines. It also uses strap-on motors to augment the thrust provided by the first stage.
- The GSLV is designed mainly to deliver the communication-satellites to the highly elliptical (typically 250 x 36000 Km) Geosynchronous Transfer Orbit (GTO).
- The satellite in GTO is further raised to its final destination, viz., Geo-synchronous Earth orbit (GEO) of about 36000 Km altitude (and zero deg inclination on equatorial plane) by firing its in-built on-board engines.
Due to their geo-synchronous nature, the satellites in these orbits appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth, thus avoiding the need of a tracking ground antenna and hence are useful for the communication application.