Orbital Regimes: LEO, MEO, GEO, HEO and what each is good for
Delta-V Academy / Learn / Lesson 7
Four altitude bands. Four totally different design philosophies.
Orbits are roughly grouped into four regimes by altitude: Low Earth Orbit (LEO, below 2,000 km), Medium Earth Orbit (MEO, 2,000-35,786 km), Geostationary Orbit (GEO, exactly 35,786 km), and Highly Elliptical Orbit (HEO, anything with extreme eccentricity). Each regime supports very different missions because each has different latency, coverage, launch cost, and lifetime characteristics. Understanding the regime is the first decision every space mission makes.
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What you'll learn
- The altitude ranges and characteristics of LEO, MEO, GEO, and HEO
- Why Starlink (LEO) and DirecTV (GEO) coexist by serving different needs
- Atmospheric drag, radiation belts, and orbital lifetime tradeoffs
- Why MEO sits in the "valley" between the inner and outer Van Allen belts
- When to use a constellation vs a single satellite
LEO: low Earth orbit, where most action happens
LEO covers 200-2,000 km altitude. Orbital periods are 90-120 minutes. Velocity is around 7.5-7.8 km/s. The ISS, Hubble, Starlink, OneWeb, and most Earth-observation satellites live here. LEO offers cheap launch (lowest delta-V), low signal latency (Starlink at 550 km has ~20 ms ping), and high spatial resolution for imaging. The downside: each satellite only covers a small patch of ground at a time. For global coverage you need a constellation of hundreds or thousands. Atmospheric drag is also significant below 500 km and limits orbital lifetime without active reboost.
MEO: where GPS lives
MEO sits between LEO and GEO, with most operational MEO satellites at altitudes between 19,000 and 23,000 km. GPS at 20,200 km, Galileo at 23,222 km, and GLONASS at 19,100 km all live here. Why MEO? Two reasons. First, 12-hour orbits at this altitude let a constellation of just 24 satellites cover the entire Earth with at least four satellites visible from any point (needed for GPS triangulation). Second, MEO sits in the "valley" between the two Van Allen radiation belts — radiation is much lower than it would be at the belt centers.
GEO: the geostationary belt
GEO is a single ring 35,786 km above the equator, where orbital period equals one sidereal day. A GEO satellite appears stationary to ground observers. DirecTV, SiriusXM, weather satellites (GOES), and many communications relays live here. GEO's advantage: one satellite can deliver continuous service to about a third of Earth. Downsides: long signal latency (~600 ms round trip), high launch cost (needs much higher delta-V than LEO), and limited slot availability since the ITU assigns specific longitudes. The GEO belt is crowded.
HEO: when you need to dwell
Highly Elliptical Orbits trade circular regularity for the ability to "hover" over a region for hours. Molniya (12-hour orbit, 63.4° inclination, e ≈ 0.74) was designed by Soviet engineers for high-latitude communications. Tundra (24-hour orbit, similar inclination, lower eccentricity) is used by some Sirius XM satellites for North American coverage. Apogee dwell time means even a small constellation (sometimes just two or three satellites) can provide continuous service to one specific region.
Frequently asked questions
What is the difference between LEO and GEO?
LEO is low Earth orbit (200-2,000 km, 90-min periods, low latency, high spatial resolution, requires constellations). GEO is geostationary orbit (exactly 35,786 km altitude, 24-hour period, single-satellite continental coverage, high latency).
Why are GPS satellites in MEO?
A 12-hour orbital period at MEO altitude lets a 24-satellite constellation provide global coverage with 4+ satellites always visible from any point on Earth (needed for triangulation). MEO also avoids the radiation-intensive Van Allen belts above and below it.
What altitude is geostationary orbit?
Exactly 35,786 km above Earth's surface, or 42,164 km from Earth's center. This is the only altitude where a circular equatorial orbit has a period equal to one sidereal day (23h 56m 4s), causing the satellite to appear stationary in the sky.
What is a HEO satellite used for?
Highly elliptical orbits exploit Kepler's second law: the satellite moves slowly near apogee and quickly near perigee. By placing apogee over a region of interest (typically high latitudes that GEO can't serve well), a HEO satellite dwells over that region for hours per orbit. Molniya orbits dwell over Russia/northern Europe; Tundra orbits dwell over North America.
Why are there no satellites at certain altitudes?
The two Van Allen radiation belts make sustained operation difficult between roughly 1,000-6,000 km (inner belt) and 13,000-60,000 km (outer belt, peaks around 25,000 km). Operational satellites cluster in LEO (below the inner belt), in the MEO "valley" between belts, and at GEO (above the outer belt).
Related lessons
- Lesson 2: Altitude and Period — Higher orbits move slower. Drag the altitude slider and watch why.
- Lesson 3: Eccentricity and Speed — Same orbit, different speeds. Drag eccentricity, watch the satellite race through perigee and crawl through apogee.
- Lesson 8: Walker Constellations — Real notation, real constellations. Why GPS uses 6 planes and Starlink uses 72.
Open it in the simulator
Delta-V Academy is a free interactive orbital mechanics simulator that runs entirely in your browser. The 10-lesson curriculum covers everything from these basics through space domain awareness, with three difficulty levels (novice, intermediate, advanced) plus a kid-friendly mode. Launch the simulator and try Lesson 7 interactively.
See also: all FAQs · full curriculum · open the simulator