Space Science and ISRO — TNPSC Group II/IIA Science
Overview
Space science has become a major TNPSC topic since ISRO's success with Chandrayaan-3, Aditya-L1, and other missions. This chapter covers the solar system, ISRO's major missions, and India's achievements in space exploration.
The Solar System
The Sun
- Central star; 99.8% of solar system mass
- Nuclear fusion — H → He; produces energy
- Surface temperature: ~5500°C; Core: ~15 million°C
- Age: ~4.6 billion years
- Distance from Earth: ~150 million km (1 AU — Astronomical Unit)
- Light takes 8 minutes to reach Earth from Sun
The Eight Planets
| Planet | Order | Size rank | Key Features |
|---|
| Mercury | 1st | 8th (smallest) | Closest to Sun; no atmosphere; extreme temperatures |
| Venus | 2nd | 6th | Hottest planet (~462°C); dense CO₂ atmosphere; spins backward |
| Earth | 3rd | 5th | Only known life; 1 moon; 71% water |
| Mars | 4th | 7th | Red planet; largest volcano (Olympus Mons); 2 moons (Phobos, Deimos) |
| Jupiter | 5th | 1st (largest) | Great Red Spot (storm); 95 moons; most massive |
| Saturn | 6th | 2nd | Prominent rings (ice and rock); 146 moons; least dense |
| Uranus | 7th | 3rd | Rotates on its side; blue-green colour (methane); 27 moons |
| Neptune | 8th | 4th | Farthest; longest year (165 Earth years); 16 moons; blue |
Dwarf Planets
- Pluto: Reclassified from planet to dwarf planet in 2006 by IAU
- Ceres: In asteroid belt between Mars and Jupiter
- Eris, Makemake, Haumea: Beyond Neptune
Key Solar System Facts
| Object | Fact |
|---|
| Largest planet | Jupiter |
| Smallest planet | Mercury |
| Hottest planet | Venus (not Mercury — Venus has greenhouse effect) |
| Closest to Sun | Mercury |
| Most moons | Jupiter (95) |
| Largest moon | Ganymede (Jupiter's moon) |
| Only planet with rings visible to naked eye | Saturn |
| Fastest planet (orbital speed) | Mercury |
| Slowest planet (orbital speed) | Neptune |
Moon
| Feature | Details |
|---|
| Distance from Earth | 384,400 km |
| Diameter | 3474 km (~1/4th Earth) |
| Gravity | 1/6th of Earth's gravity |
| Orbital period | 27.3 days (sidereal); 29.5 days (synodic/lunar month) |
| Same side faces Earth | Synchronous rotation |
| Atmosphere | Negligible |
| Water ice | Found at poles (confirmed by Chandrayaan-1, 2008) |
Lunar Phases
New Moon → Waxing Crescent → First Quarter → Waxing Gibbous → Full Moon → Waning Gibbous → Last Quarter → Waning Crescent → New Moon
ISRO — Key Facts
| Aspect | Details |
|---|
| Founded | August 15, 1969 |
| Headquarters | Bengaluru, Karnataka |
| Father of Indian Space Programme | Dr. Vikram Sarabhai |
| First Chairman | Dr. Vikram Sarabhai |
| Current Chairman | S. Somanath (2022–) |
Key ISRO Centres
| Centre | Location | Function |
|---|
| SDSC (Satish Dhawan Space Centre) | Sriharikota, Andhra Pradesh | Launch facility |
| VSSC (Vikram Sarabhai Space Centre) | Thiruvananthapuram, Kerala | Rocket development |
| SAC (Space Applications Centre) | Ahmedabad, Gujarat | Satellite payloads |
| ISAC/UR Rao Space Centre | Bengaluru | Satellite development |
| NRSC | Hyderabad | Remote sensing |
India's Launch Vehicles
| Rocket | Full Form | Use |
|---|
| PSLV | Polar Satellite Launch Vehicle | Workhorse; most successful |
| GSLV | Geosynchronous Satellite Launch Vehicle | Heavy payload; cryogenic engine |
| LVM3 (GSLV Mk III) | Launch Vehicle Mark III | Heaviest; Chandrayaan-3, Gaganyaan |
| SSLV | Small Satellite Launch Vehicle | Small satellites; quick launch |
PSLV-C37 (2017): World record — launched 104 satellites in one mission
Major ISRO Missions
Chandrayaan-1 (2008)
| Feature | Details |
|---|
| Launch | October 22, 2008 |
| Rocket | PSLV-C11 |
| Significance | First Indian Moon mission; Moon Impact Probe crashed on Moon's surface |
| Discovery | Confirmed presence of water ice on the Moon (2009) — most significant finding |
| Contact lost | August 28, 2009 |
Chandrayaan-2 (2019)
| Feature | Details |
|---|
| Launch | July 22, 2019 |
| Rocket | GSLV Mk III-M1 |
| Components | Orbiter, Vikram Lander, Pragyan Rover |
| Outcome | Orbiter successful (still operational); Vikram lander crashed during landing (September 6, 2019) |
Chandrayaan-3 (2023) — Most Important
| Feature | Details |
|---|
| Launch | July 14, 2023 |
| Rocket | LVM3-M4 |
| Landing | August 23, 2023 — near Moon's South Pole |
| Landing site | Named "Shiv Shakti Point" |
| Components | Propulsion Module, Vikram Lander, Pragyan Rover |
| India's achievement | 4th country to soft-land on Moon; 1st to land near South Pole |
| Significance | Found evidence of sulphur at lunar south pole |
| Rover | Pragyan operated for 14 Earth days |
Mangalyaan — Mars Orbiter Mission (MOM, 2013–2022)
| Feature | Details |
|---|
| Launch | November 5, 2013 (from SDSC, Sriharikota) |
| Mars orbit insertion | September 24, 2014 (first attempt success) |
| Cost | Rs 450 crore (~$74 million) — cheapest Mars mission |
| India's record | 4th country to reach Mars; 1st Asian nation to orbit Mars on first attempt |
| Contact lost | September 2022 (fuel exhausted) |
Aditya-L1 (2023)
| Feature | Details |
|---|
| Launch | September 2, 2023 |
| Destination | Lagrange Point 1 (L1) — 1.5 million km from Earth |
| Entered halo orbit | January 6, 2024 |
| Purpose | India's first solar observatory mission |
| Payloads | 7 scientific instruments studying corona, solar wind, magnetic fields |
GSAT Communication Satellites
- India has 50+ communication satellites (INSAT/GSAT series)
- Used for TV broadcasting, weather forecasting, disaster management
RISAT/Cartosat (Observation Satellites)
- Cartosat: High-resolution earth observation; defence and civilian use
- RISAT (Radar Imaging Satellite): Works in all weather
Gaganyaan — India's Crewed Mission
| Feature | Details |
|---|
| Mission | India's first crewed space flight |
| Rocket | LVM3 |
| Status | Astronauts (Vyomnauts) selected; uncrewed test missions underway (2024) |
| Target | Carry 3 Indians to 400 km orbit for 3 days |
| Significance | India becomes 4th country with own crewed space capability |
| Astronauts selected | Group Captain Prashanth Balakrishnan Nair, Ajit Krishnan, Angad Pratap, Shubhanshu Shukla |
Key Space Achievements of India
| Achievement | Year | Mission |
|---|
| First Indian satellite | 1975 | Aryabhata (launched by USSR) |
| First satellite from Indian soil | 1980 | Rohini (RS-1) by SLV-3 |
| First remote sensing satellite | 1988 | IRS-1A |
| First Moon mission | 2008 | Chandrayaan-1 |
| First Mars mission | 2013 | Mangalyaan |
| 104 satellites in one launch | 2017 | PSLV-C37 |
| Soft landing near Moon's South Pole | 2023 | Chandrayaan-3 |
| First solar observatory | 2023 | Aditya-L1 |
Key Facts for TNPSC Group II/IIA
- ISRO founded: August 15, 1969; headquarters Bengaluru
- Dr. Vikram Sarabhai: Father of Indian Space Programme; India's first rocket launch was from Thumba, Thiruvananthapuram (1963)
- PSLV: India's workhorse rocket; launched Chandrayaan-1, Mangalyaan
- LVM3 (GSLV Mk III): Heaviest rocket; used for Chandrayaan-3 and Gaganyaan
- Chandrayaan-1 (2008): Confirmed water ice on Moon
- Chandrayaan-3 (2023): Soft landed near South Pole on August 23, 2023; named "Shiv Shakti Point"
- Mangalyaan (2014): India reached Mars on first attempt; cheapest Mars mission ($74 million)
- Aditya-L1 (2023): India's first solar mission; at Lagrange Point 1
- Venus is hottest planet (not Mercury) due to greenhouse effect
- Jupiter: Largest planet; Great Red Spot; most moons (95)
Previous Year MCQ Patterns
Q: India's Chandrayaan-3 successfully soft-landed on the Moon on: a) July 14, 2023 b) August 23, 2023 c) September 2, 2023 d) January 6, 2024
Answerb) August 23, 2023 — Chandrayaan-3's Vikram lander made a successful soft landing near the Moon's South Pole on August 23, 2023. This made India the 4th country to achieve a soft lunar landing and the 1st to land near the South Pole. The landing site was named "Shiv Shakti Point" by PM Modi.
Q: Mangalyaan made India the first Asian country to successfully orbit Mars. In which year did it enter Mars orbit? a) 2013 b) 2014 c) 2015 d) 2016
Answerb) 2014 — Mangalyaan (Mars Orbiter Mission) was launched on November 5, 2013, and successfully entered Mars orbit on September 24, 2014 — on the very first attempt. India became the 4th country to reach Mars (after USSR, USA, Europe) and the only country to succeed on the first try.
Q: Aditya-L1, India's first solar mission, was positioned at which Lagrange Point? a) L2 b) L3 c) L1 d) L4
Answerc) L1 — Aditya-L1 was placed in a halo orbit at the Sun-Earth Lagrange Point 1 (L1), approximately 1.5 million km from Earth. From this position, the spacecraft can continuously observe the Sun without any occultation (without the Earth or Moon blocking the view). It entered the L1 halo orbit on January 6, 2024.
