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Launch vehicles, satellites and applications

Launch vehicles, satellites and what they are used for: rockets and their engines, Earth observation, communication and navigation satellites, orbits, and the launches of each year. Prelims has asked about the orbits of the Indian Regional Navigation Satellite System (IRNSS) satellites and the uses of Indian Remote Sensing satellites.

UPSC has asked

  • Prelims 2023: countries with their own satellite navigation system
  • Prelims 2018: the orbits of the IRNSS satellites
  • Prelims 2018: India's satellite launch vehicles and the orbits they serve
  • Prelims 2015: uses of Indian Remote Sensing satellites

4 Sep 2026 · Prelims and Mains

EOS-05

Geosynchronous orbit is new ground for Indian Earth observation, and EOS-05 is the first to image from it. Which orbit a satellite is given decides what its pictures can show and how often they arrive, so the choice is made against what the images are for.

Satellite orbit bands, not to scaleLow Earth orbit from 160 to 2,000 km, medium Earth orbit from 2,000 to 35,786 km, and geosynchronous orbit at about 35,786 km, where EOS-05 operates.Geosynchronous orbitAbout 35,786 km upOne orbit a day, matching Earth's spinCommunication, weather, now EOS-05Medium Earth orbit2,000 to 35,786 km upNavigation constellations,such as GalileoLow Earth orbit160 to 2,000 km upOne orbit every 90 to 120 minutesMost imaging satellites, the ISSEOS-05Earth

Closer to Earth. Finer detail, but a satellite races past and sees a place only briefly.

Farther from Earth. A wide region watched continuously, in coarser detail.

Not to scale. Altitudes as given in The Indian Express, 5 September 2026.
  • A Geosynchronous Satellite Launch Vehicle (GSLV-F17) carried EOS-05 to orbit.
  • Also called Geo Imaging Satellite 1A (GISAT-1A), it images chosen areas at frequent intervals for disaster monitoring, agriculture and forestry.
  • It replaces GISAT-1, lost in 2021 when the cryogenic upper stage of its GSLV failed to ignite.
  • A satellite in low Earth orbit sees fine detail, but its revisit time runs to days.
  • A satellite in geosynchronous orbit watches one large region continuously, in coarser detail, and spends fuel on station keeping.
  • Only a satellite in geostationary orbit appears fixed in the sky, while other geosynchronous orbits trace a path across it over the day.
  • What these satellites see feeds the Landslide Atlas of India, the monitoring of glacial lake outburst floods, and the National Database for Emergency Management 5.0.

PIB, 4 Sep 2026: Prime Minister hails the launch of GSLV-F17 carrying EOS-05 (opens in a new tab) · The Indian Express, 5 Sep 2026: ISRO launches EOS-05: What are the different types of satellite orbits, and why do they matter? (opens in a new tab)

13 Aug 2026 · Prelims and Mains

Recent and forthcoming ISRO missions

Prelims asks what each mission was first to do, which is why this is worth holding as a list rather than as a history. Besides EOS-05 and Aditya-L1 above, these are the missions ISRO has recently flown and those it has approved or planned.

  • 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.
  • SPADEX (Space Docking Experiment) made India the fourth country to dock two spacecraft in orbit.
  • NISAR (NASA-ISRO Synthetic Aperture Radar), flown with the National Aeronautics and Space Administration (NASA) of the United States, 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.
  • The Venus Orbiter Mission is planned.
  • Chandrayaan-4 is to bring a lunar sample back to Earth.
  • LUPEX (Lunar Polar Exploration), also called Chandrayaan-5, is planned with the Japan Aerospace Exploration Agency (JAXA).

PIB, 13 Aug 2026: Recap of recent and upcoming ISRO missions (opens in a new tab)

11 Aug 2026 · Prelims and Mains

Everest and full-flow staged combustion

The cycle an engine runs on decides how much of its propellant ends as thrust, and how hard the engine is to build. Full-flow staged combustion is the demanding end of that choice, which is why so few countries have flown it.

  • A Bengaluru startup unveiled Everest, an 800 kN engine, making India the fourth country with full-flow staged combustion technology after Russia, the United States and China.
  • It burns liquid oxygen and methane, a pair called methalox that leaves little soot.
  • The cycle throttles precisely and suits reusable rockets.

The Hindu, 11 Aug 2026: What is the significance of India's first privately built FFSC rocket engine? (opens in a new tab)

Also filed elsewhere

Prelims and Mains

Also drawn on: The Hindu, 5 Sep 2026

Last updated 19 Sep 2026.

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