A LEO satellite is any spacecraft orbiting Earth at an altitude of 2,000 kilometers (1,200 miles) or less. This relatively close proximity to the planet’s surface gives LEO satellites distinct advantages: they circle the Earth in roughly 90 minutes, deliver data with minimal delay, and can capture high-resolution images of the ground below. The majority of all active satellites operate in this zone, including the International Space Station and large internet constellations like Starlink.
How Low Earth Orbit Works
To stay in orbit at LEO altitudes, a satellite needs to travel at approximately 7.8 kilometers per second, or about 17,000 miles per hour. At that speed, the satellite is essentially falling toward Earth but moving forward fast enough that it keeps missing it. The balance between gravitational pull and forward momentum creates a stable, circular path around the planet.
Because they’re so close to Earth, LEO satellites complete a full revolution every 90 minutes or so. That means a single satellite passes over many different parts of the globe throughout the day rather than hovering over one fixed spot. This is a fundamental difference from satellites in higher orbits.
LEO Compared to Other Orbits
Earth orbit is typically divided into three main altitude bands. LEO sits closest to the surface, extending from roughly 160 km up to 2,000 km. Medium Earth Orbit (MEO) picks up above that, stretching from about 2,000 km to 35,786 km. GPS navigation satellites operate in MEO. Geostationary orbit (GEO) sits at exactly 35,786 km, where a satellite’s orbital period matches Earth’s rotation, making it appear to hover over one point on the equator.
The altitude difference has a direct impact on signal delay. A signal traveling to a GEO satellite and back covers roughly 72,000 km round-trip, producing latency of 550 to 1,000 milliseconds. LEO satellites, being so much closer, deliver latency of just 20 to 100 milliseconds. That’s a gap you can feel: GEO latency creates noticeable lag on video calls, while LEO latency is comparable to a home broadband connection.
What LEO Satellites Are Used For
The low altitude makes LEO ideal for several categories of work. Earth observation satellites capture detailed imagery for weather forecasting, agriculture monitoring, disaster response, and military intelligence. Being closer to the surface means sharper images with smaller, less expensive cameras.
Broadband internet is the fastest-growing use case. Companies are deploying massive constellations of LEO satellites to deliver high-speed, low-latency internet coverage across the globe, including rural and remote areas that terrestrial networks don’t reach. These constellations are increasingly seen as a complement to 5G and future 6G cellular networks, not a replacement but an extension that fills coverage gaps.
Scientific research also relies heavily on LEO. The International Space Station orbits at about 400 km, and numerous smaller satellites study everything from ocean temperatures to gravitational fields. Military communications and reconnaissance satellites frequently operate in LEO as well, taking advantage of the short signal travel time and high-resolution observation capability.
Why LEO Satellites Don’t Last Forever
Unlike satellites in higher orbits, LEO spacecraft deal with atmospheric drag. Even at hundreds of kilometers above the surface, trace amounts of atmosphere create friction that gradually slows a satellite and lowers its orbit. At altitudes around 400 to 500 km, a dead satellite will slow down and burn up in the atmosphere within a few years. At 800 to 900 km, that natural decay process takes centuries. At 1,000 km and above, debris can persist for millennia.
This drag means LEO satellites need periodic boosts to maintain their altitude. They carry onboard propulsion systems and use small amounts of fuel to nudge themselves back up. Once the fuel runs out or a component fails, the satellite’s operational life ends. The FCC now requires all licensed LEO satellites to deorbit within five years of completing their mission, a significant tightening from the previous 25-year guideline, aimed at reducing the amount of dead hardware circling overhead.
The Orbital Debris Problem
LEO is getting crowded. As of mid-2023, nearly 6,800 active satellites were operating in low Earth orbit, and that number continues to climb as new constellations launch. More satellites mean a higher chance of collisions, and collisions create debris that can trigger further collisions.
This cascading risk has a name: the Kessler Syndrome, first described by NASA scientist Donald Kessler in the late 1970s. The most notable real-world example came in 2009, when an active Iridium communications satellite collided with a defunct Russian Cosmos satellite, generating roughly 2,000 trackable debris fragments. Experts consider that event an early demonstration of the problem Kessler predicted.
The concern isn’t that LEO would become completely unusable overnight. It’s a gradual degradation. As debris accumulates, operating in certain orbital bands becomes riskier and more expensive. Satellites need more frequent maneuvers to dodge debris, and the probability of losing a spacecraft to a collision goes up. Models show that if space traffic grows too large without adequate debris management, debris populations at certain altitudes could grow exponentially, making those orbital lanes impractical to use.
Altitude matters here too. Below about 500 km, atmospheric drag naturally cleans up debris within a few years. But at 800 to 1,000 km, where many Earth observation satellites operate, debris lingers for centuries or longer. A collision event at those altitudes could spiral into a serious, long-term problem far more quickly than one closer to Earth’s surface.
How LEO Shapes Constellation Design
Because a single LEO satellite can only see a small slice of the Earth at any given moment and passes overhead quickly, you need many of them working together to provide continuous coverage. This is why modern LEO internet services deploy hundreds or thousands of satellites arranged in coordinated orbital shells. Each satellite hands off your connection to the next one as it moves out of range, creating seamless coverage from the user’s perspective.
This constellation approach is fundamentally different from GEO, where three well-placed satellites can cover nearly the entire planet. LEO trades that simplicity for lower latency, stronger signals, and the ability to serve users at high latitudes where GEO coverage is weak. The tradeoff is cost and complexity: building, launching, and managing thousands of satellites requires a scale of infrastructure that only became economically viable with reusable rockets and cheaper small-satellite manufacturing.