Satellite Orbits: Types, Working, and Complete Explanation

Introduction

An orbit is the curved path that a spacecraft, planet, moon, star, or any other object follows under the gravitational pull of another body. The gravitational attraction between massive objects in space causes them to orbit one another when the force is strong enough.

A satellite or spacecraft is launched into specific orbits around Earth, or it may be sent on an interplanetary mission to orbit the Sun until it reaches its destination, such as Mars or Jupiter.

The ideal orbit for a satellite depends on its purpose. The major types of orbits are:

• Geostationary Orbit (GEO)
• Low Earth Orbit (LEO)
• Medium Earth Orbit (MEO)
• Polar Orbit and Sun-Synchronous Orbit (SSO)
• Transfer Orbit and Geostationary Transfer Orbit (GTO)
• Lagrange Points (L-Points)

Geostationary Orbit (GEO)

A geostationary orbit is an orbit in which satellites move at the same rotational speed as Earth, completing one rotation in 23 hours, 56 minutes, and 4 seconds. This makes GEO satellites appear stationary over a specific point on the equator.

GEO satellites must travel at about 3 km/s at an altitude of 35,786 km to match Earth’s rotation. Because of this high altitude, GEO satellites cover a large area of Earth.

Telecommunication and weather satellites commonly use GEO because ground antennas can remain fixed at one point. Only three satellites spaced evenly in GEO can provide near-global coverage.

Low Earth Orbit (LEO)

A Low Earth Orbit lies within 160 km to 1000 km above Earth’s surface. Although low compared to other orbits, it is still far above commercial airplane altitude.

Unlike GEO satellites, LEO satellites can have various orbital inclinations. Their close proximity to Earth allows high-resolution imaging, making LEO ideal for Earth observation satellites.

The International Space Station (ISS) also operates in LEO. Satellites here travel at about 7.8 km/s, completing one orbit in 90 minutes. Due to their fast movement, individual LEO satellites cannot provide continuous coverage, so they operate in large constellations (e.g., Starlink).

Medium Earth Orbit (MEO)

Medium Earth Orbit ranges from 2,000 km to 35,786 km above Earth. MEO lies between LEO and GEO. MEO satellites have orbital periods of less than 24 hours, with the shortest period being around 2 hours.

Solar radiation pressure and Earth’s albedo affect satellites in MEO. The Van Allen radiation belts also exist here, requiring additional shielding for satellite electronics.

MEO is commonly used for navigation systems such as GPS, GLONASS, and Galileo.

Polar Orbit and Sun-Synchronous Orbit (SSO)

A Sun-Synchronous Orbit (SSO) is a special type of polar orbit. Satellites in SSO pass over polar regions while maintaining a consistent local time when crossing the equator.

This ensures consistent lighting conditions, which is essential for accurate Earth observation and environmental monitoring.

Since satellites capture sunlight reflected from Earth’s surface, maintaining consistent solar illumination helps scientists compare multi-day or multi-week imagery without large lighting variations.

Transfer Orbits and Geostationary Transfer Orbit (GTO)

Transfer orbits are used to move satellites from one orbit to another. Satellites are often not directly placed into their final orbit by launch vehicles. Instead, they are inserted into a transfer orbit.

A Geostationary Transfer Orbit (GTO) is a widely used elliptical orbit that moves a satellite from low Earth orbit to GEO. Once the payload reaches apogee, it fires its engines to enter the circular GEO orbit.

This method saves energy and reduces the workload on the launch vehicle.

Lagrange Points (L-Points)

Lagrange points are special locations where the gravitational forces of two large bodies balance out, allowing a smaller object to remain in a stable or semi-stable position.

In the Earth–Sun system, spacecraft can orbit the Sun while maintaining a fixed position relative to Earth at these points. There are five Lagrange points: L1, L2, L3, L4, and L5.

Stability of Lagrange Points

• L1: Unstable; located between Earth and the Sun. Ideal for solar observation.
• L2: Unstable; located 1.5 million km from Earth on the opposite side of the Sun. Used for deep-space telescopes.
• L3: Unstable; located beyond the Sun, opposite Earth.
• L4: Stable; located 60° ahead of Earth in its orbit.
• L5: Stable; located 60° behind Earth.