What is ISRO and where is it headquartered?

ISRO stands for Indian Space Research Organisation. It is India's national space agency, headquartered in Bengaluru (Bangalore), Karnataka. It was established in 1969.

What was special about Chandrayaan-3?

Chandrayaan-3 (2023) successfully landed the Vikram lander and deployed the Pragyan rover near the lunar south pole, making India the first country to land near the lunar south pole and the fourth country overall to soft-land on the Moon.

What is a geostationary satellite?

A geostationary satellite orbits Earth at the same speed as Earth's rotation, appearing stationary over a fixed point on the equator. It orbits at about 36,000 km altitude. Used for weather forecasting, TV broadcasting, and communication.

Who is called the Father of the Indian Space Programme?

Dr. Vikram Sarabhai is called the Father of the Indian Space Programme. He founded the Physical Research Laboratory (PRL) and established the first rocket launching station at Thumba, Kerala.

Space Science and ISRO — TNPSC Group 4 Science Notes

Overview

Space science questions in TNPSC Group 4 focus on the solar system, ISRO missions, and Indian space achievements. With Chandrayaan-3's success in 2023 and India's growing space ambitions, this topic carries increasing importance. Expect 2–3 questions per paper.

The Solar System

Planets (in order from the Sun)

Mnemonic: My Very Excited Mother Just Served Us Nachos

Planet	Type	Notable Feature
Mercury	Rocky	Closest to Sun; no atmosphere; extreme temperature variation
Venus	Rocky	Hottest planet (dense CO₂ atmosphere); rotates backward; brightest object after Sun and Moon
Earth	Rocky	Only planet with life; 71% water; one moon
Mars	Rocky	"Red planet" (iron oxide surface); largest volcano (Olympus Mons); 2 moons
Jupiter	Gas Giant	Largest planet; Great Red Spot (storm); 95 moons
Saturn	Gas Giant	Famous ring system; least dense planet (floats on water)
Uranus	Ice Giant	Rotates on its side (tilted 98°); coldest planet
Neptune	Ice Giant	Farthest planet; strongest winds in solar system

TNPSC Tip: Pluto was reclassified as a dwarf planet by the IAU in 2006.

The Sun

A G-type main-sequence star (yellow dwarf)
Composition: ~73% Hydrogen, ~25% Helium
Core temperature: ~15 million°C
Surface temperature: ~5,500°C
Distance from Earth: ~150 million km (1 Astronomical Unit)
Solar flares — eruptions of energy; can disrupt satellite communications

Moons and Key Natural Satellites

Moon	Parent Planet	Notable For
Moon	Earth	Only natural satellite of Earth; 27.3-day orbit
Ganymede	Jupiter	Largest moon in solar system
Titan	Saturn	Has thick atmosphere; liquid methane lakes
Europa	Jupiter	Possible subsurface ocean; candidate for life

Other Solar System Objects

Object	Description
Asteroid Belt	Between Mars and Jupiter; rocky debris
Comets	Icy bodies; form tails when near Sun; e.g., Halley's Comet (76-year period)
Meteoroid	Small rock in space; meteorite when it hits Earth
Dwarf Planets	Pluto, Ceres, Eris, Makemake, Haumea

Types of Satellites

Orbit	Altitude	Use
LEO (Low Earth Orbit)	200–2,000 km	Earth observation, ISS, spy satellites
MEO (Medium Earth Orbit)	2,000–36,000 km	GPS, navigation
GEO (Geostationary Orbit)	~36,000 km	Weather, TV broadcast, communication
Polar Orbit	~800 km	Remote sensing, covers entire Earth

ISRO — Indian Space Research Organisation

Key Facts

Detail	Information
Founded	1969
Headquarters	Bengaluru, Karnataka
Chairperson (2024)	S. Somanath
Father of Indian Space Programme	Dr. Vikram Sarabhai
Launch Vehicles	PSLV, GSLV, LVM3 (GSLV Mk III)
Main Launch Site	Satish Dhawan Space Centre, Sriharikota (Andhra Pradesh)
First rocket launch	1963, Thumba, Kerala (using a bicycle to transport rocket parts)

Launch Vehicles

Vehicle	Full Name	Known For
PSLV	Polar Satellite Launch Vehicle	Reliable workhorse; Chandrayaan-1, MOM
GSLV	Geosynchronous Satellite Launch Vehicle	Heavier payloads; cryogenic engine
LVM3 / GSLV Mk III	Launch Vehicle Mark 3	Heaviest; used for Chandrayaan-3, OneWeb launches

Major ISRO Missions

Moon Missions

Mission	Year	Achievement
Chandrayaan-1	2008	First Indian lunar mission; discovered water molecules on Moon
Chandrayaan-2	2019	Orbiter successful; Vikram lander crashed on surface
Chandrayaan-3	2023	First soft landing near lunar south pole; Vikram + Pragyan rover; 4th country to land on Moon

Mars Mission

Mission	Year	Achievement
Mangalyaan (MOM — Mars Orbiter Mission)	2013 (launch) / 2014 (orbit)	First Asian country to reach Mars orbit; first attempt success in the world; lowest-cost Mars mission

Sun Mission

Mission	Year	Achievement
Aditya-L1	2023	India's first solar observatory; placed at Lagrange Point 1 (L1) between Earth and Sun

Earth Observation and Communication

Satellite Series	Purpose
IRS (Indian Remote Sensing)	Mapping, agriculture, disaster management
INSAT (Indian National Satellite System)	Communication, weather forecasting
IRNSS / NavIC	Indian Regional Navigation Satellite System — GPS equivalent for India
GSAT	Communication satellites

Other Notable Missions

Mission	Achievement
SLV-3 (1980)	First Indian satellite launch vehicle; placed Rohini satellite in orbit
PSLV-C37 (2017)	World record — launched 104 satellites in one rocket
RLV-TD	Reusable Launch Vehicle technology demonstrator
Gaganyaan	India's first crewed spaceflight (upcoming); will send Indian astronauts to space

India's First Astronauts / Cosmonauts

Name	Mission	Year
Rakesh Sharma	Soyuz T-11 (Soviet mission)	1984	First Indian in space; said "Saare Jahan Se Accha" from space

Gaganyaan Mission (Upcoming)

India's first crewed space mission
Will carry Indian astronauts (Vyomanauts) to space
Launch vehicle: LVM3

Universe — Big Picture

Term	Description
Light Year	Distance light travels in one year ≈ 9.46 × 10¹² km
Galaxy	Collection of billions of stars; our galaxy = Milky Way
Big Bang	Theory of universe origin (~13.8 billion years ago)
Black Hole	Region of extreme gravity where nothing escapes — not even light
Nebula	Cloud of gas and dust where stars form

Previous Year TNPSC Questions (Pattern)

1. Q: ISRO headquarters is located in → Bengaluru 2. Q: Mangalyaan was launched in → 2013 3. Q: India's first lunar mission → Chandrayaan-1 (2008) 4. Q: Which is the hottest planet? → Venus 5. Q: Father of Indian Space Programme → Dr. Vikram Sarabhai 6. Q: Chandrayaan-3 landed near → Lunar south pole 7. Q: PSLV-C37 set a world record by launching → 104 satellites 8. Q: First Indian to go to space → Rakesh Sharma (1984)

Frequently Asked Questions

Jupiter is the largest planet in the solar system. It is a gas giant and has 95 known moons, the largest being Ganymede (largest moon in the solar system).