ISRO's launch vehicles and the orbits they serve

Prelims and MainsCurrent affairs on this: Launch vehicles, satellites and applications

A launch vehicle is chosen by two numbers: how heavy the payload is and which orbit it must reach. Low Earth orbit (LEO) is where Earth observation satellites, the space station and new constellations fly; a Sun synchronous polar orbit (SSO) is a low orbit that passes over any place at the same local time each day, which imaging needs; geostationary transfer orbit (GTO) is the ellipse from which a communication satellite climbs to the geostationary ring at 35,786 km. The higher orbit costs far more energy, so a vehicle carries much less to GTO than to LEO. ISRO flies the Small Satellite Launch Vehicle (SSLV), the Polar Satellite Launch Vehicle (PSLV), the Geosynchronous Satellite Launch Vehicle (GSLV) Mk II and LVM3, with the Next Generation Launch Vehicle (NGLV) under development.

• Orbit decides the vehicle: SSO for imaging (PSLV), GTO for communication (GSLV, LVM3), LEO for small satellites and crew (SSLV, LVM3).
• Cryogenic stages (liquid hydrogen and liquid oxygen) give the highest efficiency and are what GSLV and LVM3 have that PSLV lacks; India's CE 7.5 and CE 20 engines are why the technology denial of the 1990s matters to the story.
• Solid stages are simple and powerful but cannot be throttled or restarted; liquid stages can, which is why upper stages are liquid.
• Payload to GTO is between a third and a half of payload to LEO for the same vehicle: exactly half for LVM3, about 37 per cent for GSLV Mk II, so one figure cannot be worked out from the other.
• All four vehicles launch from Sriharikota. A second spaceport at Kulasekarapattinam, in Thoothukudi district, will serve SSLV, private small launchers and sounding rockets; its value is a direct southward launch that avoids the dogleg manoeuvre needed from Sriharikota, which costs payload to polar orbit. The foundation stone was laid on 28 February 2024. The PSLV lost EOS-09 in May 2025 and EOS-N1 in January 2026 to third stage failures, which ISRO attributes to components not made in house; a third launch pad is being built at Sriharikota for next generation vehicles, and India has crossed 100 launches from there.
• Recent firsts to hold as a list: Chandrayaan-3 made the first soft landing near the lunar south pole on 23 August 2023; XPoSat is India's first X-ray polarimetry mission; the Space Docking Experiment (SPADEX) made India the fourth country to dock two spacecraft in orbit; the NASA-ISRO Synthetic Aperture Radar (NISAR), flown with NASA, is the first Earth observation satellite to carry radar in both the L and S bands; GSAT-7R (CMS-03) is a communications satellite for the Navy; EOS-05 is the first Indian Earth observation satellite in geosynchronous orbit.

Mains: India's launch capacity was gated for two decades by the cryogenic engine; with LVM3 proven and NGLV approved, the constraint has moved from technology to cost per kilogram and launch cadence, which is why the private launchers matter.

Further reading: Launchers (ISRO) · Catalog of Earth satellite orbits (NASA)

See also: Vikram-1 · Everest and full-flow staged combustion · Indian Space Policy 2023 · Gaganyaan