Low Earth orbit, commonly called LEO, is the region of space within about 1,200 miles (2,000 km) above Earth’s surface. It’s where the International Space Station flies, where most satellite constellations operate, and where the vast majority of human spaceflight has taken place. If you’ve used satellite internet, watched a rocket launch on a livestream, or followed astronauts on social media, you’ve already been connected to low Earth orbit in some practical way.
How High Is Low Earth Orbit?
LEO starts at roughly 100 to 200 miles above Earth, where the atmosphere thins out enough that a spacecraft can complete at least one full orbit without immediately burning up from air resistance. The upper boundary sits at about 1,200 miles (2,000 km). Beyond that point, you enter medium Earth orbit, home to GPS satellites and other navigation systems.
The lower end of LEO is constrained by the atmosphere itself. Below about 186 miles (300 km), residual air molecules create so much drag that a satellite loses altitude quickly and falls back to Earth. The upper boundary exists for a different reason: the inner Van Allen radiation belt. This zone of trapped charged particles can damage electronics and solar cells, making it a poor neighborhood for long-term satellite operations. So LEO occupies a practical sweet spot between too much air and too much radiation.
Objects in LEO travel at roughly 17,000 miles per hour (about 7.8 km/s) and complete a full orbit in approximately 90 minutes. That speed is what keeps them from falling back to Earth. They’re essentially falling around the planet so fast that the curve of Earth drops away beneath them at the same rate.
What’s Actually Up There?
LEO is the most crowded orbital zone. Space surveillance networks now track about 40,000 objects in orbit, of which roughly 11,000 are active satellites. The rest are spent rocket stages, defunct spacecraft, and fragments from collisions and explosions. The European Space Agency estimates that over 1.2 million debris objects larger than 1 centimeter are circling Earth, each one capable of causing catastrophic damage to a working satellite.
The International Space Station is the most recognizable resident, orbiting at about 250 miles (408 km). China’s Tiangong space station operates at a similar altitude. But the real population boom comes from satellite mega-constellations. SpaceX’s Starlink network, designed to deliver broadband internet worldwide, operates its primary shell at about 340 miles (550 km), with additional shells planned at higher and lower altitudes. Amazon’s Project Kuiper and other operators are building similar constellations. The ESA projects that around 100,000 satellites could be in orbit by 2030.
At an altitude of about 550 km, there are now roughly as many debris objects posing a collision threat as there are active satellites. That ratio is a growing concern for the long-term sustainability of LEO operations.
Why LEO Matters for Internet and Communications
Satellites in LEO orbit much closer to Earth than traditional communications satellites, which sit in geostationary orbit about 22,000 miles up. That proximity dramatically reduces latency, the delay between sending a signal and receiving a response. A signal bouncing to a geostationary satellite and back takes roughly 600 milliseconds for a round trip. From LEO, that delay drops to around 20 to 40 milliseconds, making real-time video calls, gaming, and other latency-sensitive applications far more practical.
The tradeoff is coverage. A single geostationary satellite can see a third of Earth’s surface because it’s so far away. A LEO satellite moves across the sky in minutes and covers a much smaller area at any given moment. That’s why Starlink and similar systems need thousands of satellites working in coordination, handing off connections as each one passes overhead, to provide continuous global coverage. The constellation approach is complex, but it solves a problem that higher orbits physically cannot: fast, responsive internet to remote and underserved areas.
Atmospheric Drag and Orbital Decay
Unlike satellites in higher orbits, LEO spacecraft face a constant battle with air resistance. The atmosphere doesn’t end with a sharp boundary. It gradually fades, and even at 250 or 550 miles up, a thin haze of air molecules creates measurable drag. This drag slowly robs a satellite of speed, causing it to spiral lower and eventually re-enter the atmosphere.
How often a satellite needs to fire its thrusters to maintain altitude depends heavily on the Sun. During quiet solar periods, the ISS and similar spacecraft boost their orbits about four times per year. But when the Sun is active, ultraviolet radiation heats the upper atmosphere and causes it to puff outward. Denser air rises to altitudes where satellites fly, increasing drag significantly. During solar maximum, the peak of the Sun’s roughly 11-year activity cycle, satellites may need to maneuver every two to three weeks just to stay in their assigned orbit.
This drag is actually useful from a debris standpoint. Objects below about 375 miles will naturally re-enter the atmosphere within a few years, which acts as a self-cleaning mechanism for the busiest part of LEO. Satellites at higher LEO altitudes, like 750 miles and above, can remain in orbit for decades or even centuries after they stop functioning, contributing to the long-term debris problem.
The Cost of Getting There
LEO is the cheapest orbital destination, though “cheap” is relative when you’re launching something into space. SpaceX’s Falcon 9 rocket can carry about 22,800 kg to LEO for around $67 million, which works out to roughly $2,940 per kilogram. The larger Falcon Heavy pushes 63,800 kg to LEO for about $97 million, dropping the cost to approximately $1,520 per kilogram. For context, the Space Shuttle era cost roughly $54,000 per kilogram to LEO, so launch prices have fallen by more than an order of magnitude in the past two decades.
This cost reduction is the single biggest reason LEO has gotten so crowded so fast. When it cost tens of thousands of dollars per kilogram, only governments and large telecom companies could afford to put hardware in orbit. At under $3,000 per kilogram, universities, startups, and smaller nations can launch satellites. Reusable rocket technology, particularly SpaceX’s ability to land and refly booster stages, has been the primary driver of this shift.
LEO Compared to Other Orbits
Earth orbit is divided into three broad zones. LEO runs from the edge of the atmosphere to about 1,200 miles. Medium Earth orbit (MEO) extends from there to roughly 22,000 miles, where you find GPS and similar navigation satellite constellations. Geostationary orbit (GEO) is a specific altitude of about 22,236 miles where a satellite’s orbital period matches Earth’s rotation, making it appear to hover over one spot on the equator. Weather satellites and traditional TV broadcast satellites typically operate in GEO.
Each zone involves tradeoffs. LEO offers low latency and relatively cheap access but requires more satellites for global coverage and demands regular maintenance against drag. MEO provides a balance for navigation systems that need precise timing across large regions. GEO gives persistent coverage of one area but at much higher latency and launch cost. The orbit you choose depends entirely on the job the satellite needs to do.
What Comes Next for LEO
NASA is preparing for a transition in how humans live and work in low Earth orbit. As the International Space Station nears the end of its operational life, NASA plans to shift from owning and operating its own station to purchasing services from commercial space stations. Several companies are developing private stations, with NASA positioning itself as one customer among many in what it calls a “low Earth orbit economy.”
The sheer volume of planned activity is staggering. Going from about 11,000 active satellites today to a projected 100,000 by 2030 means the population of LEO could increase nearly tenfold within a few years. Managing collision risk, coordinating orbits, and tracking debris at that scale will require new international agreements and more capable surveillance networks. LEO is no longer a frontier visited by a few government agencies. It’s rapidly becoming shared infrastructure, as essential to daily life as undersea cables or cell towers.