Low Earth orbit
Published 19 October 2026 · All guides
In short: low Earth orbit (LEO) is anything up to about 2,000 km above the surface. Satellites there go round in roughly 90 to 127 minutes. It is close, so cameras see sharply and radio links are quick, and it is cheap to reach. The costs are that each satellite sees a place only briefly, air drag slowly pulls it down, and it is the most crowded and debris-strewn region of space.
How high and how fast
The lowest practical orbits are around 160 km; below that, drag brings a satellite down within days. The usual upper limit quoted is 2,000 km. Across that band a lap takes from about 88 minutes at the bottom to about 127 at the top, at speeds of 7 to 8 km/s. Satellites in low orbit go round the Earth around fifteen times a day.
What lives there
- Crewed stations. The International Space Station flies at about 420 km, China's Tiangong at a similar height.
- Imaging satellites, commercial and military, mostly between about 250 and 800 km, because detail falls with distance (see how spy satellites work).
- Internet constellations. SpaceX's Starlink satellites fly at around 550 km, thousands of them, because a short hop to the ground keeps delay low.
- Telescopes. Hubble has orbited in LEO since 1990, low enough to be visited and repaired by the Space Shuttle.
The advantages
Being close is the whole point. A camera resolves finer detail, a radio needs less power, and the trip to orbit costs less, so more mass goes up per launch. Low orbits are also reachable for servicing, as Hubble's five Shuttle repair missions showed.
The costs
- Brief visits. At 7.5 km/s a low satellite is over any one place for a few minutes, and then the Earth's rotation moves the next pass elsewhere. Continuous watch needs many satellites.
- Drag. The thin upper atmosphere slows satellites and lowers them, faster when solar activity heats it. Staying up costs propellant.
- Darkness. A low satellite spends roughly a third of each orbit in the Earth's shadow, running on batteries.
- Debris. LEO is where most of the debris is. In January 2007 China destroyed its Fengyun-1C weather satellite with a missile, creating more than 3,000 tracked fragments. In February 2009 the active Iridium 33 and the defunct Russian Kosmos 2251 collided at about 790 km. In November 2021 Russia destroyed Kosmos 1408 in another anti-satellite test, forcing the ISS crew to shelter.
Two special low orbits
A polar orbit, tilted near 90 degrees, passes over every part of the Earth as the planet turns beneath it. A sun-synchronous orbit is a near-polar orbit whose tilt is chosen so it passes over each place at the same local time every day, which is why imaging satellites favour it.
Where Celestrike comes in
Celestrike starts you in low orbit. Its low imagers fly at 620 km, where they see finely but only briefly, and its signals satellites a little higher. Every satellite pays upkeep in propellant to stay where it is. Celestrike is a free spy-satellite strategy game for iPhone and Android, played on real orbits — on the App Store and Google Play.