Satellites are launched using rockets that fly above most of the atmosphere in a curved path around Earth. When the rocket gets to a specific distance from Earth, it will release the satellite.

The satellite stays in orbit because it still has momentum – energy it picked up from the rocket – pulling it in one direction. Earth’s gravity pulls it in another direction. This balance between gravity and momentum keeps the satellite orbiting around Earth.

Satellites that orbit close to Earth feel a stronger tug of Earth’s gravity. To stay in orbit, they must travel faster than a satellite orbiting farther away.

The International Space Station orbits about 420km above the Earth and travels at a speed of about 27,500km per hour. Compare that to the tracking and data relay satellites, which help us get information to and from other NASA missions.

These satellites orbit at a height of more than 35,000km above the Earth’s surface and travel much slower – about 10,500km per hour – to maintain their high orbit.