Types of Orbits & Satellites: LEO, MEO, GEO & SSO Explained Simply

A satellite doesn't "float." It is constantly falling toward Earth because of gravity — but it also moves forward so fast that Earth's surface curves away beneath it at the same rate. The result is a stable orbit: perpetual falling that never reaches the ground.

Two numbers to lock in:

• Orbital velocity (to stay in a low orbit): about 7.9 km/s (~28,000 km/h).
• Escape velocity (to break free of Earth's gravity completely): 11.2 km/s.

1. LEO — Low Earth Orbit

• Closest to Earth (160–2,000 km). Satellites here move fastest and circle Earth in about 90 minutes.
• Being close gives high-resolution images and low signal delay — but each satellite sees only a small patch, so you need many of them for full coverage.
• Examples: the ISS (~400 km), the Hubble Telescope, most Earth-observation & spy satellites, and the Starlink constellation.
• Drawback: more atmospheric drag → shorter satellite life.

2. MEO — Medium Earth Orbit

• Sits between LEO and GEO (2,000 – 35,786 km).
• Home of navigation systems: GPS (USA) orbits at ~20,200 km; GLONASS, Galileo and BeiDou also use MEO.
• Passes through the Van Allen radiation belts, so satellites need radiation shielding.

3. GEO — Geostationary Earth Orbit

• A single, exact altitude: 35,786 km above the equator.
• Its period equals Earth's rotation (~24 hrs) and it moves in the same direction as Earth — so it appears to stay fixed at one point in the sky. That's why your TV dish never moves.
• Just 3 GEO satellites, spaced 120° apart, can cover almost the entire globe.
• Examples: India's INSAT and GSAT series (communication + weather).

These sound identical but they are not:

• Geosynchronous orbit: period = 24 hrs, but the orbit can be tilted (inclined). From the ground the satellite traces a figure-of-8 and drifts north–south.
• Geostationary orbit: a special case of geosynchronous — 24-hr period AND zero inclination (directly over the equator). It appears completely stationary.

Polar Orbit

• The satellite passes over (or near) the North and South Poles each revolution — inclination close to 90°.
• As it goes pole-to-pole, Earth rotates beneath it, so it scans the entire planet, strip by strip.
• Ideal for mapping, reconnaissance and Earth observation. Usually low altitude (LEO).

SSO — Sun-Synchronous Orbit MOST CONFUSED

• A special type of near-polar LEO (altitude usually 600–800 km, inclination ~98°).
• Defining feature: the satellite crosses over any given point at the same local solar time every day.
• Why it matters: the sunlight angle is always the same, so images from different days are directly comparable — ideal for tracking crops, forests, floods and urban growth.
• This is the workhorse orbit for remote-sensing satellites. Indian examples: Cartosat, Resourcesat, RISAT and the IRS series — launched mainly by PSLV.

GTO — Geostationary Transfer Orbit

• Not a destination but a highway: a highly elliptical orbit used to carry a satellite up to GEO. The satellite fires its own engine at the high point to circularise into the final orbit.
• Rockets like GSLV / LVM3 drop communication satellites into GTO.

Molniya / Highly Elliptical Orbit (HEO)

• A stretched elliptical orbit that lingers for hours over high-latitude regions (e.g. Russia), where equator-parked GEO satellites give poor coverage.

• Communication satellites — TV, phone, internet. Sit in GEO. India: GSAT, INSAT.
• Navigation satellites — positioning. Global systems use MEO. India: NavIC / IRNSS (see below).
• Earth-observation / remote-sensing — imaging land, oceans, crops. SSO / polar LEO. India: Cartosat, Resourcesat, RISAT.
• Weather satellites — INSAT series (GEO); some in polar orbit.
• Scientific satellites — e.g. AstroSat (space observatory), Aditya-L1 (Sun study at the L1 point).
• Military / spy satellites — usually LEO for sharp images.

So if a question asks "Which orbit does NavIC use?" the answer is GEO + GSO, not MEO.