Low Earth orbit

A low Earth orbit (LEO) is an orbit around Earth that takes 128 minutes or less to finish. This means a satellite can circle our planet more than eleven times in one day. Most human-made things in outer space, like communication satellites and pieces of space junk, are in LEO. These objects usually float at an altitude of about 800 kilometers, though some go up to 2,000 kilometers above Earth.

The area below 2,000 kilometers is called the LEO region. Even if a spacecraft goes higher or doesn’t stay here all the time, it still passes through the LEO region. Because there are many satellites here, scientists watch everything in this space to stop collisions.

Only a few special missions have gone beyond LEO. The Apollo program from 1968 to 1972 went to the Moon, and in 2026, the Artemis II mission will fly around the Moon. Every space station we’ve built so far, including the International Space Station, orbits in the LEO region.

Defining characteristics

Low Earth orbit (LEO) is a place where objects fly around Earth. Many people measure LEO by how high the object is above Earth. But the height can change a lot, even for objects that fly in a circle. Most definitions say LEO is where objects take about 128 minutes to go around Earth once.

The LEO region is the space where these orbits are. Some objects might fly through this region but not stay there because they go too high. It is important to know the difference when thinking about objects bumping into each other in space.

Orbital characteristics

To stay in a stable low Earth orbit, a spacecraft needs to move at about 7.8 kilometers per second. This speed helps it stay in orbit around Earth. The exact speed can change a little depending on how high the orbit is.

In low Earth orbit, the pull of Earth's gravity is almost the same as it is on the ground. But because the spacecraft is moving so fast, it keeps falling around Earth without ever hitting it. This is why astronauts inside these spacecraft feel like they are floating.

Low Earth orbits are special because they are close to Earth. They are high enough to avoid most of the atmosphere but low enough to not get too much radiation from the Van Allen belts. Some of these orbits can help satellites quickly check on places near the equator, while others can cover more of the Earth.

Use

A low Earth orbit is a special path around our planet that uses very little energy. Satellites in this orbit can send information quickly and clearly. They are also easier for people to reach for repairs or upgrades.

Because these satellites can only see a small part of Earth at a time, we need many of them to keep the whole world connected. These satellites orbit close to Earth and can move slowly. Sometimes they need a little help to stay in their path.

Some well-known satellites and space stations are in low Earth orbit, like the International Space Station and the Hubble Space Telescope. Others help us connect to the internet from anywhere on Earth, such as Starlink. Many satellites that watch Earth, like those used for weather or maps, also fly in this special orbit.

Space debris

The area around Earth called low Earth orbit is getting crowded with pieces of old satellites and other objects. This is called space debris. It can be dangerous because these pieces move very fast. If two pieces hit each other, they can break into even more tiny pieces. This can keep happening and cause problems for satellites and spacecraft.

NASA keeps track of many of these pieces. They watch over 25,000 objects that are bigger than about the size of a small book. There are also many smaller pieces that are harder to see, and they all move at very high speeds. Even a tiny piece can cause big damage when it hits something in space.