edVirtus Reference

What Are the Common Satellite Orbits?

What Are LEO, MEO, HEO and GEO?

Artificial satellites are placed into different orbits depending on their intended purpose. The four principal orbital categories are Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Highly Elliptical Orbit (HEO), and Geostationary Earth Orbit (GEO). Each offers distinct advantages and disadvantages in terms of coverage, propagation delay, launch cost, satellite lifetime, and the number of satellites required to provide continuous service.

Low Earth Orbit (LEO) extends from approximately 160 km to 2,000 km above the Earth's surface. Satellites in LEO complete an orbit in about 90 to 130 minutes and move rapidly across the sky relative to an observer on the ground. Their proximity to the Earth results in low propagation delay and relatively low free-space path loss, making them well suited to Earth observation, remote sensing, imaging, scientific missions, and modern broadband communication constellations such as Starlink, OneWeb, and Amazon Project Kuiper. Because each satellite covers only a relatively small area of the Earth's surface, dozens or even thousands of satellites are required to provide continuous global coverage.

Medium Earth Orbit (MEO) lies between approximately 2,000 km and 35,786 km altitude. MEO satellites have orbital periods ranging from about 2 hours to 24 hours and provide much wider coverage than LEO satellites while maintaining lower latency than geostationary satellites. Their most familiar application is satellite navigation, with systems such as GPS, Galileo, GLONASS, and BeiDou operating primarily in MEO. Only a few dozen satellites are required for continuous global navigation coverage.

Highly Elliptical Orbit (HEO) differs from the previous categories because it is defined by its shape rather than its altitude. Instead of following a nearly circular orbit, an HEO satellite travels in a highly elongated ellipse, spending much of each orbit near apogee, where it moves relatively slowly. Well-known examples include the Molniya and Tundra orbits, which provide prolonged coverage of high-latitude regions that are difficult to serve using geostationary satellites. HEO systems are particularly valuable for communications, weather monitoring, and surveillance in Arctic and Antarctic regions.

Geostationary Earth Orbit (GEO) is a special circular orbit located at an altitude of approximately 35,786 km directly above the Earth's equator. At this altitude, the satellite's orbital period is exactly one sidereal day, matching the Earth's rotation. As a result, the satellite appears stationary in the sky when viewed from the ground. This unique characteristic allows fixed ground antennas to communicate continuously with the satellite without tracking it. GEO is widely used for communications, television broadcasting, meteorology, and data relay because a single satellite can view approximately one-third of the Earth's surface. The principal disadvantage is the relatively long propagation delay, with a one-way signal delay of approximately 120 ms.

A useful analogy is to imagine four types of aircraft. LEO satellites resemble low-flying aircraft that pass overhead quickly but provide detailed local coverage. MEO satellites are comparable to high-altitude aircraft covering much larger areas. HEO satellites are like aircraft that spend extended periods circling above a particular region before moving away. GEO satellites are analogous to helicopters hovering continuously above the same point, providing uninterrupted coverage of a fixed area.

It is important to distinguish GEO from geosynchronous orbit. Every geostationary satellite is geosynchronous because it has a 24-hour orbital period. However, not every geosynchronous satellite is geostationary. A satellite must also have a circular orbit with zero inclination to remain fixed above a single point on the equator.

Today, all four orbital regimes play essential roles in modern space systems. LEO supports broadband communications and Earth observation, MEO provides global navigation services, HEO delivers extended coverage of high-latitude regions, and GEO enables continuous communications and weather monitoring. Together, these orbital regimes allow satellite systems to meet a wide range of scientific, commercial, military, and civilian requirements across the globe.