Space for UPSC: ISRO Launch Vehicles, Orbits, NavIC, GAGAN, NISAR, SpaDeX, Axiom-4 and Gaganyaan

How UPSC Tests Space

🎯 Exam priority: Tier-1. Space is 17 of 104 Science and Technology Prelims questions in ten years (16 per cent), with ISRO news driving most of them. UPSC asked: Astrosat and the Mars Orbiter Mission (2016); uses of GPS, the IRNSS and India's satellite launch vehicles (2018); remote-sensing uses (2019); which country has its own navigation system (2023); GAGAN (2025); and private participation in the space programme (2026). Mains asked India's space achievements (2016), a manned mission (2017), a space station (2019), Chandrayaan-3 (2023) and Mission Drishti (2026).

Three boxes: the machines (rockets and orbits), the services (navigation and remote sensing) and the 2025-26 missions.

Launch Vehicles and Orbits

Rockets and orbits

• Orbits: low Earth orbit (hundreds of km), sun-synchronous polar orbit (about 500 to 800 km, used by Earth-observation satellites such as EOS-09 at 505 km), geosynchronous transfer orbit and geostationary orbit (about 36,000 km), where a satellite stays fixed over one spot on the equator. Satellites that seem fixed in the sky are geostationary, not PSLV's polar ones (2018 PYQ).

• Electric propulsion: in March 2025 ISRO completed a 1,000-hour life test of a 300 mN stationary plasma thruster using xenon, with a specific impulse at least six times that of conventional propulsion, to replace chemical thrusters for orbit raising.

• Semi-cryogenic engine: the 2,000 kN-class SE2000 engine is being developed for the SC120 stage that will replace the liquid core of LVM3.

Navigation and Remote Sensing

Navigation and remote sensing

• IRNSS (NavIC) has seven satellites: three in geostationary and four in geosynchronous orbit. It is a regional system covering India and about 1,500 km around it, not a global one (2018 PYQ). The second-generation NVS series began with NVS-02 in January 2025, which was left in an elliptical orbit because valves to feed oxidiser to its thrusters did not open.

• Other systems: GPS (USA), GLONASS (Russia), Galileo (EU), BeiDou (China) and the Quasi-Zenith Satellite System (Japan). Of the countries Australia, Canada, Israel and Japan, only Japan has its own system (2023 PYQ).

• GAGAN (GPS Aided Geo Augmented Navigation) is an ISRO and Airports Authority system of ground stations that improves the accuracy and integrity of GPS signals; it helps air traffic management and also other modes such as rail and maritime transport (2025 PYQ).

• Uses of GPS: besides location, its timing signal is used by mobile networks, banks and power grids (2018 PYQ).

• Remote sensing estimates chlorophyll in vegetation, greenhouse-gas emissions from rice paddies and land surface temperature (2019 PYQ). In 2025 ISRO's CROP framework used optical and radar satellites (EOS-04, EOS-06, Resourcesat-2A) to estimate wheat area of 330.8 lakh hectares by 31 March 2025. ISRO also took the six-month lead role in the International Charter on Space and Major Disasters from April 2025.

The 2025-26 ISRO Year and How UPSC Could Ask Next

The 2025-26 ISRO year

ISRO also developed the first fully Make-in-India 32-bit microprocessor for launch vehicles (VIKRAM3201), and scientists at PRL, Ahmedabad found the exoplanet TOI-6038A b with the PARAS-2 spectrograph. Aditya-L1 released its first batch of scientific data on 6 January 2025, a year after entering its halo orbit at the Sun-Earth L1 point.

2026: Mission Drishti (secondary sources)

Mission Drishti, launched on 3 May 2026 on a SpaceX Falcon 9, is a private satellite built by the Bengaluru start-up GalaxEye. It is India's first OptoSAR satellite: it combines an optical (multispectral) imager and a synthetic-aperture radar on one platform, which is why it is called the first of its kind.

How UPSC Could Ask This Next

• Vehicle facts: stages, fuel and the orbit each vehicle serves.

• Services: NavIC, GAGAN, NISAR and what each sensor type (optical, radar) is good for.

• Missions: SpaDeX docking, Axiom-4, Gaganyaan, Aditya-L1, private launches.

• Policy: IN-SPACe, NSIL, Space Policy 2023 and Vision 2047.

Further Reading

• NCERT Biology (Class 12) and Geography textbooks, the India State of Forest Report, the MoEFCC Annual Report, the Economic Survey and the official lists cited in this note — the primary sources behind every figure above.

Test Yourself: Practice Questions and PYQs

Twelve practice questions on launch vehicles, navigation, remote sensing and the 2025-26 ISRO missions, followed by the real UPSC Prelims questions and exact Mains questions.

Practice Questions

Q1. Which of the following is a geostationary orbit characteristic?

• (a) A satellite orbits at about 500 km above the Earth

• (b) A satellite stays fixed over one point on the equator at about 36,000 km

• (c) A satellite orbits the Moon

• (d) A satellite passes over the poles every orbit

Q2. The Indian Regional Navigation Satellite System (IRNSS, NavIC) consists of

• (a) 24 satellites in medium Earth orbit

• (b) five polar satellites

• (c) seven geostationary satellites

• (d) three geostationary and four geosynchronous satellites

Q3. Which of the following countries has its own regional satellite navigation system?

• (a) Japan

• (b) Canada

• (c) Australia

• (d) Israel

Q4. GAGAN is a system developed by ISRO and the Airports Authority of India that

• (a) improves the accuracy and integrity of GPS signals

• (b) tracks missiles

• (c) measures ocean temperature

• (d) launches small satellites

Q5. The first joint satellite of ISRO and NASA, launched on GSLV-F16 on 30 July 2025, is

• (a) CMS-03

• (b) NVS-02

• (c) EOS-09

• (d) NISAR

Q6. Consider the following statements about the SpaDeX mission:
1. Two satellites were launched by PSLV-C60.
2. They docked in space on 16 January 2025.
3. Power transfer between the docked satellites was tested in April 2025.
Which of the statements given above are correct?

• (a) 1 and 2 only

• (b) 2 and 3 only

• (c) 1 and 3 only

• (d) 1, 2 and 3

Q7. CROPS (Compact Research Module for Orbital Plant Studies) germinated seeds of which plant in orbit?

• (a) Wheat

• (b) Cowpea

• (c) Rice

• (d) Mustard

Q8. The heaviest communication satellite launched to geosynchronous transfer orbit from India, CMS-03, was carried by

• (a) GSLV-F15

• (b) LVM3-M5

• (c) SSLV

• (d) PSLV-C61

Q9. Who became the first Indian astronaut to visit the International Space Station, on the Axiom-4 mission?

• (a) Ajit Krishnan

• (b) Prasanth Nair

• (c) Rakesh Sharma

• (d) Shubhanshu Shukla

Q10. India's space agency has set which target for an Indian crewed lunar landing?

• (a) By 2040

• (b) By 2030

• (c) By 2060

• (d) By 2025

Q11. The Small Satellite Launch Vehicle (SSLV) is

• (a) a reusable spaceplane

• (b) a cryogenic heavy-lift rocket

• (c) a liquid-fuelled two-stage rocket

• (d) a three-stage all-solid vehicle for satellites up to about 500 kg

Q12. Mission Drishti, launched in May 2026, is described as the first satellite of its kind because it

• (a) is placed at the Sun-Earth L1 point

• (b) combines an optical imager and a synthetic aperture radar on one platform

• (c) is a communication satellite

• (d) carries a hyperspectral camera only

UPSC Previous Year Questions (PYQs)

Real UPSC Prelims questions, checked against the official paper and answer key.

Q1. (2016) With reference to 'Astrosat',' the astronomical observatory launched by India, which of the; following statements is/are correct?
1. Other than the USA and Russia, India is the only country to have launched a similar observatory into space.
2. Astrosat is a 2000 kg satellite placed in an orbit at 1650 km above the surface of the Earth.
Select the correct answer using the code given below.

• (a) Neither 1 nor 2

• (b) Both 1 and 2

• (c) 2 only

• (d) 1 only

Q2. (2016) Consider the following statements: The Mangalyaan launched by ISRO 1. is also called the Mars Orbiter Mission 2. made India the second country to have a spacecraft orbit the Mars after USA 3. made India the only country to be successful in making its spacecraft orbit the Mars in its very first attempt Which of the statements given above is/are correct?

• (a) 2 and 3 only

• (b) 1, 2 and 3

• (c) 1 only

• (d) 1 and 3 only

Q3. (2018) In which of the following areas can GPS technology be used?
1. Mobile phone operations
2. Banking operations
3. Controlling the power grids
Select the correct answer using the code given below:

• (a) 1, 2 and 3

• (b) 1 only

• (c) 2 and 3 only

• (d) 1 and 3 only

Q4. (2018) With reference to the Indian Regional Navigation Satellite System (IRNSS), consider the following statements:
1. IRNSS has three satellites in geostationary and four satellites in geosynchronous orbits.
2. IRNSS covers entire India and about 5500 sq. km beyond its borders.
3. India will have its own satellite navigation system with full global coverage by the middle of 2019.
Which of the statements given above is/are correct?

• (a) None

• (b) 2 and 3 only

• (c) 1 and 2 only

• (d) 1 only

Q5. (2018) With reference to India's satellite launch vehicles, consider the following statements:
1. PSLVs launch the satellite useful for Earth resources monitoring whereas GSLVs are designed mainly to launch communication satellites.
2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location in Earth.
3. GSLV Mk III is a four-staged launch vehicle with the first and third stages using solid rocket motors; and the second and fourth stages using liquid rocket engines.
Which of the statements given above is/are correct?

• (a) 1 and 2

• (b) 1 only

• (c) 2 and 3

• (d) 3 only

Q6. (2019) For the measurement/estimation of which of the following are satellite images/remote sensing data used?
1. Chlorophyll content in the vegetation of a specific location
2. Greenhouse gas emissions from rice paddies of a specific location
3. Land surface temperatures of a specific location
Select the correct answer using the code given below.

• (a) 1 only

• (b) 3 only

• (c) 1, 2 and 3

• (d) 2 and 3 only

Q7. (2023) Which one the following countries has its own Satellite Navigation System?

• (a) Japan

• (b) Australia

• (c) Canada

• (d) Israel

Q8. (2025) GPS-Aided Geo Augmented Navigation (GAGAN) uses a system of ground stations to provide necessary augmentation. Which of the following statements is/are correct in respect of GAGAN?
1. It is designed to provide additional accuracy and integrity.
2. It will allow more uniform and high quality air traffic management.
3. It will provide benefits only in aviation but not in other modes of transportation.
Select the correct answer using the code given below.

• (a) 2 and 3 only

• (b) 1 only

• (c) 1 and 2 only

• (d) 1, 2 and 3

Q9. (2026, provisional key) Consider the following statements with regard to involvement of private entities in India's space programme :
1. The Indian National Space Promotion and Authorisation Centre (IN-SPACe) is an autonomous agency formed to facilitate participation of private entities.
2. Agnikul Cosmos launched the world's first flight using 3D-printed rocket engine.
3. Skyroot Aerospace has developed liquid fuel for GSLV.
Which of the statements given above is/are correct?

• (a) 2 and 3 only

• (b) 1 and 2 only

• (c) 1, 2 and 3

• (d) 1 only

Mains Practice Questions

Use these to frame full-length answers. You don't have to answer one exactly — they show the angles UPSC tests, so let them guide which points you cover.

• Discuss India's achievements in the field of Space Science and Technology. How has the application of this technology helped India in its socio-economic development?

• What is India's plan to have its own space station and how will it benefit the space programme?

• India has achieved remarkable success in unmanned space missions but has not ventured into manned missions. What are the main obstacles to launching a manned mission?

• What is the main task of India's third moon mission which could not be achieved earlier? List the countries that have achieved it.

• Mention the salient features of Mission Drishti and the imaging techniques used. Why is it considered the world's first of its kind?

UPSC Mains — Previous Years’ Questions on this topic (last 10 years)

These are the actual GS Mains questions UPSC has asked on this theme — real proof of how, and when, it is tested. Try to write a full answer to each.

• 2026 (GS-III): Mention salient features of 'Mission Drishti'. Discuss the imaging techniques used in the satellite launched on 3rd May 2026. Why it is being considered world's first satellite of its kind?

• 2023 (GS-III): What is the main task of India's third moon mission which could not be achieved in its earlier mission? List the countries that have achieved this task. Introduce the subsystems in the spacecraft launched and explain the role of the 'Virtual Launch Control Centre' at the Vikram Sarabhai Space Centre which contributed to the successful launch from Sriharikota.

• 2019 (GS-III): What is India's plan to have its own space station and how will it benefit our space programme?

• 2017 (GS-III): India has achieved remarkable successes in unmanned space missions including the Chandrayaan and Mars Orbiter Mission, but has not ventured into manned space missions. What are the main obstacles to launching a manned space mission, both in terms of technology and logistics? Examine critically.

• 2016 (GS-III): Discuss India's achievements in the field of Space Science and Technology. How the application of this technology has helped India in its socio-economic development?