Quick Answer: Satellite Types, Orbits, and PSLV vs GSLV vs SSLV at a Glance
ISRO Satellite Types and Launch Vehicles: PSLV, GSLV, SSLV Complete Guide
Quick Answer: ISRO operates three main launch vehicles — PSLV (light, reliable workhorse for polar/LEO missions), GSLV/LVM3 (heavy-lift with indigenous cryogenic engines for GTO and interplanetary missions), and SSLV (low-cost, quick-turnaround launcher for small satellites). Chandrayaan-3 and Mangalyaan flew on LVM3/GSLV variants, while satellites occupy LEO (Earth observation), MEO (navigation like NavIC), and GEO (communication like INSAT) orbits.
- Quick Answer: Satellite Types, Orbits, and PSLV vs GSLV vs SSLV at a Glance
- Why Satellites and Launch Vehicles Matter in UPSC, SSC, and Banking Exams
- Types of Satellites by Function: Communication, Navigation, Earth Observation, Scientific
- Types of Orbits: LEO, MEO, GEO, and Polar/SSO Explained Simply
- PSLV: The Workhorse of ISRO
- GSLV and LVM3: Heavy-Lift Capability with Indigenous Cryogenic Engines
- SSLV: The New Small Satellite Launcher
- Comparison Table: PSLV vs GSLV vs SSLV Payload, Orbit, and Use Case
- ISRO Missions Timeline: 1975 to Present
- Landmark Missions in Detail: Chandrayaan-3, Mangalyaan, Aditya-L1
- Previous Year Questions (PYQs) on Satellites and Launch Vehicles
- One-Page Revision Notes and Memory Tricks for Exam Day
- Frequently Asked Questions
- Q: Which is more powerful, PSLV or GSLV?
- Q: Which launch vehicle carried Chandrayaan-3?
- Q: What is the full form of PSLV, GSLV, and SSLV?
- Q: At what altitude do GEO and LEO satellites orbit?
- Q: What was ISRO’s first satellite?
- Related reading
| Feature | PSLV | GSLV / LVM3 | SSLV |
|---|---|---|---|
| Payload to LEO/SSO | ~1,750 kg to SSO | Up to 8,000 kg (LVM3, LEO) | Up to 500 kg to LEO |
| Payload to GTO | Not designed for GTO | ~2,250 kg (GSLV Mk II); ~4,000 kg (LVM3) | Not applicable |
| Stages | 4 stages (alternating solid/liquid) | 3 stages with cryogenic upper stage | 3 stages (solid-dominated) |
| Key missions | Chandrayaan-1, 104-satellite record (C37), EOS/Cartosat | Chandrayaan-2 & 3, Mangalyaan, Gaganyaan (planned) | SSLV-D2/EOS-07 (2023) |
| Best use case | Remote sensing, polar launches, smallsat rideshares | Heavy communication satellites, deep-space missions | Fast, on-demand small satellite launches |
Why Satellites and Launch Vehicles Matter in UPSC, SSC, and Banking Exams
Space technology is a permanent fixture in Indian competitive exams. UPSC Prelims has repeatedly asked about ISRO missions (Chandrayaan, Mangalyaan, Aditya-L1), orbit types, and cryogenic technology. SSC CGL and Banking GA sections frequently test full forms (PSLV, GSLV, NavIC), launch dates, and firsts (first satellite, first lunar landing site). Current affairs segments cover new launches like SSLV-D2 and Gaganyaan test flights. A single well-organised revision of vehicles, orbits, and the missions timeline can secure 2–4 marks in almost every exam cycle.
Types of Satellites by Function: Communication, Navigation, Earth Observation, Scientific
- Communication Satellites: Relay TV, telephone, and broadband signals. Indian examples: INSAT series (starting 1983) and GSAT series, placed in GEO.
- Navigation Satellites: Provide position data. India’s NavIC (Navigation with Indian Constellation) uses 7 IRNSS satellites in GEO/GSO.
- Earth Observation (Remote Sensing) Satellites: Monitor land, water, agriculture, and disaster. Indian examples: IRS series, Cartosat, RISAT, EOS satellites — mostly in polar/SSO.
- Scientific Satellites: Study space phenomena. Examples: AstroSat (2015, India’s first astronomy observatory), Aditya-L1 (solar study), Chandrayaan lunar probes.
Types of Orbits: LEO, MEO, GEO, and Polar/SSO Explained Simply
| Orbit | Altitude | Key Feature | Typical Users |
|---|---|---|---|
| LEO (Low Earth Orbit) | ~200–2,000 km | Low latency, fast orbital speed, short life | ISS, Earth observation (Cartosat, EOS) |
| MEO (Medium Earth Orbit) | ~2,000–35,000 km | Wider coverage per satellite | GPS, GLONASS, Galileo, part of NavIC ground segment tracking |
| GEO (Geostationary Orbit) | ~35,786 km | Satellite appears stationary; matches Earth’s rotation | INSAT/GSAT communication, INSAT weather, NavIC GEO satellites |
| Polar / Sun-Synchronous (SSO) | ~500–800 km (usually LEO) | Passes over poles; same local time each pass | IRS, Cartosat, most Earth-observation satellites |
PSLV specialises in polar/SSO launches; GSLV/LVM3 dominate GTO (Geostationary Transfer Orbit) insertions from which satellites climb to GEO.
PSLV: The Workhorse of ISRO
The Polar Satellite Launch Vehicle (PSLV) is ISRO’s most reliable launcher, with dozens of successful flights since 1993. It is a four-stage vehicle alternating solid and liquid stages, capable of placing about 1,750 kg into a 600 km Sun-synchronous orbit.
- 1993: First PSLV flight (PSLV-D1).
- 2008: PSLV-C11 launched Chandrayaan-1, India’s first lunar probe.
- 2017: PSLV-C37 set a world record by launching 104 satellites in a single flight.
- 2022: PSLV-C53 demonstrated the PSLV Orbital Experimental Module (POEM).
Earlier milestones include PSLV-C34 (2016, 20 satellites) and C53 (2022, 3 Singaporean satellites). Its versatility in rideshare and multi-orbit deployments makes it the preferred launcher for national and foreign small satellites. Details are documented on ISRO’s official site (isro.gov.in).
GSLV and LVM3: Heavy-Lift Capability with Indigenous Cryogenic Engines
The Geosynchronous Satellite Launch Vehicle (GSLV) was developed to place heavy communication satellites (~2,250 kg) into GTO. Its defining feature is the indigenous cryogenic upper stage engine, the CE-7.5, which ISRO mastered after years of technology denial — a landmark in self-reliance, operational since the GSLV Mk II’s first success in 2014 (GSLV-D5 with GSAT-14).
The GSLV Mk III, now renamed LVM3, is India’s heaviest lifter: two S200 solid boosters, L110 liquid core, and the C25 cryogenic stage powered by the CE-20 engine. It can lift ~4,000 kg to GTO and ~8,000 kg to LEO. LVM3 launched:
- Chandrayaan-2 (2019)
- Chandrayaan-3 (2023)
- OneWeb commercial batches (2022–23)
- It is the designated vehicle for the human spaceflight programme Gaganyaan.
SSLV: The New Small Satellite Launcher
The Small Satellite Launch Vehicle (SSLV) is ISRO’s compact three-stage launcher designed to place up to 500 kg into LEO. Its advantages: low cost, quick turnaround (launch readiness in days rather than months), and minimal infrastructure — ideal for universities, startups, and constellations. After the partial failure of SSLV-D1 (2022), SSLV-D2 successfully placed EOS-07 and two co-passengers in orbit in February 2023, proving the design.
Comparison Table: PSLV vs GSLV vs SSLV Payload, Orbit, and Use Case
| Parameter | PSLV | GSLV Mk II | LVM3 (GSLV Mk III) | SSLV |
|---|---|---|---|---|
| Height | ~44 m | ~49 m | ~43 m | ~34 m |
| Stages | 4 | 3 | 3 | |
| Cryogenic engine | None | CE-7.5 | CE-20 | None |
| Mass at liftoff | ~320 tonnes | ~414 tonnes | ~640 tonnes | ~120 tonnes |
| Payload to LEO/SSO | ~3,800 kg LEO / 1,750 kg SSO | ~5,000 kg LEO | ~8,000 kg LEO | ~500 kg LEO |
| Payload to GTO | — | ~2,250 kg | ~4,000 kg | — |
| Notable missions | Chandrayaan-1, PSLV-C37, EOS series | GSAT series, NVS-01 | Chandrayaan-2/3, OneWeb, Gaganyaan | EOS-07 (SSLV-D2) |
ISRO Missions Timeline: 1975 to Present
- 1975: Aryabhata — India’s first satellite (launched by Soviet Kosmos-3M).
- 1980: Rohini RS-1 — first Indian satellite launched from Indian soil, on SLV-3 from Sriharikota.
- 1983: INSAT-1B — operational start of the INSAT communication system.
- 1993: First PSLV flight.
- 2001: First GSLV flight (GSLV-D1) with Russian cryogenic stage.
- 2008: Chandrayaan-1 (PSLV-C11) — discovered water molecules on the Moon.
- 2013: PSLV-C25 launched Chandrayaan-2 — see below.
- 2014: First successful indigenous cryogenic flight (GSLV-D5).
- 2013: Mangalyaan (Mars Orbiter Mission) launched by PSLV-C25; entered Mars orbit September 2014 — India first nation to succeed on first attempt.
- 2015: AstroSat — India’s first space observatory.
- 2017: PSLV-C37 launches 104 satellites.
- 2019: Chandrayaan-2 (LVM3-M1) — orbiter still active; lander Vikram hard-landed.
- 2023: SSLV-D2/EOS-07; Chandrayaan-3 soft landing (23 August); Aditya-L1 launch (2 September).
- 2024: Aditya-L1 reaches halo orbit around L1 (January); Gaganyaan test flights progress.
Verify dates against official sources such as ISRO and PIB before the exam.
Landmark Missions in Detail: Chandrayaan-3, Mangalyaan, Aditya-L1
Chandrayaan-3 (2023): Launched on LVM3-M4 on 14 July 2023; the Vikram lander soft-landed near the lunar south pole on 23 August 2023, making India the first country to do so and the fourth to soft-land on the Moon. The Propulsion Module placed the mission in a lunar orbit; the Pragyan rover conducted in-situ experiments.
Mangalyaan / Mars Orbiter Mission (2013–14): Launched on PSLV-C25 on 5 November 2013; entered Mars orbit on 24 September 2014. India became the first nation to reach Mars orbit on its maiden attempt, and ISRO the first Asian agency to do so — at roughly ₹450 crore, among the cheapest Mars missions ever.
Aditya-L1 (2023): India’s first solar mission, launched on PSLV-C57 on 2 September 2023; inserted into a halo orbit around the L1 Lagrange point (~1.5 million km from Earth) on 6 January 2024, carrying seven payloads to study the solar corona and solar wind.
Previous Year Questions (PYQs) on Satellites and Launch Vehicles
- Q: Which launch vehicle was used for Chandrayaan-3?
A: LVM3 (GSLV Mk III) — launched 14 July 2023. - Q: India’s first satellite was —
A: Aryabhata, 1975. - Q: The cryogenic engine used in GSLV Mk II’s upper stage is —
A: CE-7.5. - Q: NavIC satellites operate primarily in which orbit?
A: Geostationary/Geosynchronous orbit (GEO/GSO). - Q: SSLV-D2 placed which satellite in orbit in February 2023?
A: EOS-07. - Q (UPSC-style): Aditya-L1 is placed in a halo orbit around —
A: Lagrange point 1 (L1).
One-Page Revision Notes and Memory Tricks for Exam Day
| Item | Memory Trick / Fact |
|---|---|
| Launch vehicles | “P-G-S = Payload Gets Smaller… backwards!” PSLV heavy-ish workhorse, GSLV heaviest, SSLV smallest (500 kg). |
| Orbits | “Low-Medium-Geo“: 2–2–36 → 200–2,000 km (LEO), 2,000–35,000 km (MEO), 35,786 km (GEO). |
| Cryogenic engines | CE-7.5 = GSLV Mk II; CE-20 = LVM3 (bigger engine, bigger number). |
| Chandrayaan-3 | 14/7 launch → 23/8 landing, south pole, LVM3. |
| Mangalyaan | PSLV-C25, Nov 2013 → Mars Sept 2014; first-attempt success. |
| Satellite families | I-N-A: INSAT (communication), NavIC (navigation), Astrosat (science) — plus IRS (observation). |
Frequently Asked Questions
Q: Which is more powerful, PSLV or GSLV?
GSLV/LVM3 is more powerful — LVM3 can lift up to ~4,000 kg to GTO and ~8,000 kg to LEO, versus PSLV’s ~1,750 kg to SSO. However, PSLV remains ISRO’s most reliable workhorse, especially for remote sensing and smallsat rideshare missions.
Q: Which launch vehicle carried Chandrayaan-3?
LVM3 (GSLV Mk III) launched Chandrayaan-3 on 14 July 2023. The Vikram lander achieved a soft landing near the lunar south pole on 23 August 2023, making India the first nation to land there.
Q: What is the full form of PSLV, GSLV, and SSLV?
Polar Satellite Launch Vehicle, Geosynchronous Satellite Launch Vehicle, and Small Satellite Launch Vehicle.
Q: At what altitude do GEO and LEO satellites orbit?
GEO satellites orbit at about 35,786 km, matching Earth’s rotation so they appear stationary. LEO satellites orbit roughly 200–2,000 km (ISS, Earth observation). MEO lies between ~2,000 and 35,000 km (navigation satellites like GPS; NavIC’s satellites sit in GEO/GSO).
Q: What was ISRO’s first satellite?
Aryabhata, launched in 1975 and named after the ancient Indian mathematician-astronomer. It was launched aboard a Soviet rocket; India’s first indigenously launched satellite was Rohini RS-1 (1980, on SLV-3).
Related reading
- Spaceports and Launch Vehicles of India: SHAR, Chandrayaan Missions and PSLV vs GSLV – Complete Exam Notes
- Semiconductor Mission India Explained: ISM Scheme, Fab Locations and PLI for Exams
Quick revision
- Communication Satellites: Relay TV, telephone, and broadband signals. Indian examples: INSAT series (starting 1983) and GSAT series, placed in GEO.
- Navigation Satellites: Provide position data. India’s NavIC (Navigation with Indian Constellation) uses 7 IRNSS satellites in GEO/GSO.
- Earth Observation (Remote Sensing) Satellites: Monitor land, water, agriculture, and disaster. Indian examples: IRS series, Cartosat, RISAT, EOS satellites — mostly in polar/SSO.
- Scientific Satellites: Study space phenomena. Examples: AstroSat (2015, India’s first astronomy observatory), Aditya-L1 (solar study), Chandrayaan lunar probes.
- 1993: First PSLV flight (PSLV-D1).
- 2008: PSLV-C11 launched Chandrayaan-1, India’s first lunar probe.
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