Classification of Orbits
Based on shape:
- Circular orbit – A circular orbit is a path on which every point is equally distant from the planet’s centre.
- Elliptical orbit – An elliptical orbit is a path where the satellite orbits in an elliptical shape around the host planet which would be at one of the two foci of that ellipse.
- Parabolic orbit – A parabolic path is a trajectory of an object used for orbital manoeuvring, where an approaching object entering the planet’s orbit is low enough to catch it and place it into the planet’s orbit, or an object already in orbit can be used to send out of it by increasing its velocity.
- Hyperbolic orbit – A hyperbolic path is a trajectory of an object used for orbital manoeuvring as well, but this is one where the approaching object already has enough speed to enter the planet’s orbit and then escape it with an adjustment to its velocity and direction. This method of manoeuvring is called gravity assist.
Based on inclination:
- Equatorial orbit – It is an orbit directly coinciding with the equator such that a satellite in this orbit stays on top of the equator throughout its orbit.
- Polar orbit – This orbit is perpendicular to the equator, passing over the poles and intersecting twice with the equatorial orbit.
- Inclined orbit – As the name suggests, it is inclined at an angle that is not parallel or perpendicular to the equator.
Based on Altitude
Suborbital Trajectory
- Taken by sounding rockets and some missiles.
- Reach upper atmosphere or space but do not complete an orbit.
- Useful for low-cost, short-duration scientific experiments.
Low Earth Orbit (LEO)
- Altitude: 180–2,000 km
- Speed: ~7.8 km/s; ~90 min per orbit
- Examples: ISS, Earth observation satellites
- Preferred for remote sensing, imaging, reconnaissance
Medium Earth Orbit (MEO)
- Altitude: 2,000–35,780 km
- Circular or elliptical
- Used for navigation satellites (e.g., NavIC, GPS)
Geostationary Orbit (GEO)
- Altitude: 35,786 km
- Appears stationary over equator; 24-hour orbital period
- Ideal for communication satellites
- Wide coverage (angular span ~81°); no need for movable antennas
Based on Inclination
Polar Orbit:
- Passes over or near both poles
- Inclined 90° or close (~70–100°)
- A form of LEO (200–1,000 km altitude)
- Covers entire Earth over time; used for environmental monitoring
Sun-Synchronous Orbit (SSO)
- A special polar orbit synchronized with the Sun
- Crosses same location at same local solar time
- Ensures consistent lighting; ideal for remote sensing & imaging
Special Orbits
Halo Orbit
- Orbits around Lagrangian points (gravitational equilibrium zones)
- Suitable for space telescopes and deep-space missions
- Example: Aditya-L1 solar mission (L1 point between Earth and Sun)
