Space Science & ISRO Basics

5 min

Satellites, Launch Vehicles and Solar System Physics

The Golden Rule of Space Science

Satellites in Geostationary Orbit match Earth's rotation to stay fixed over one spot. ISRO's PSLV is the versatile workhorse, while GSLV carries heavy payloads using cryogenic engines. Gravity and Kepler's Laws define the physics of our solar system.

Why Study Space Science?

1-2 direct marks in SSC CGL and Railway NTPC General Science sections.
Crucial for Defence (CDS/NDA) and CAPF technology-based questions.
Frequent updates in Current Affairs regarding ISRO's latest missions.

Memory Hooks

GEO-36: Geostationary height is 36,000 km (roughly).
PSLV-4: PSLV has 4 stages (Solid-Liquid-Solid-Liquid).
GSLV-Cryo: GSLV uses Cryogenic engine in its 3rd stage.

Comparison: PSLV vs GSLV

Feature	PSLV	GSLV
Stages	4 Stages	3 Stages
Fuel Type	Solid & Liquid	Cryogenic (Top)
Capacity	1750 kg (SSO)	2500 kg (GTO)

Visual Space Concepts

PSLV

(ISRO Workhorse)

ISRO Workhorse

Used for Chandrayaan-1 and Mangalyaan.

GSLV Mk III

(LVM3 / Bahubali)

LVM3 / Bahubali

Launched Chandrayaan-3 and Gaganyaan tests.

GEO Orbit

(36,000 km Height)

36,000 km Height

Satellite stays fixed over Earth's equator.

Venus

(Hottest Planet)

Hottest Planet

Hottest due to Greenhouse effect, not distance.

Common Exam Traps

PSLV is a 3-stage rocketPSLV is a 4-stage rocket

It alternates between Solid (1st/3rd) and Liquid (2nd/4th) fuel stages.

Mercury is the hottest planetVenus is the hottest planet

Venus has a thick CO2 atmosphere that traps heat like a greenhouse.

GEO satellites revolve in 12 hoursGEO satellites revolve in 24 hours

They must match Earth's 24-hour rotation to stay fixed.

Test Your Knowledge

Q1.What is the approximate altitude of a Geostationary satellite?

Q2.Which fuel type is used in the 3rd stage of GSLV?

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