What is a satellite?

Tim Peake Mascot Illustration

A satellite is an object that orbits around another object. They can be naturally occuring, like planets or moons, or built by humans, like satellites. Our Moon is a satellite of the Earth. The Earth, and the other planets in our solar system, are satellites of the Sun.

How do objects stay in orbit?

An orbit is a curved path, like a circle or an oval.

A moving object will continue moving unless something pushes or pulls on it (Newton’s first law of motion). Without gravity, a satellite would fly off into space. With gravity, a satellite is constantly pulled back toward Earth. It’s this tug-of war that keeps the satellite in orbit.

Why build satellites?

After developing technology to leave Earth’s atmosphere, we wanted things to stay in space for longer to increase their usefulness. Placing objects into the orbit of Earth, creating an artificial satellite, is a good way to do this.

Power in space

If satellites stop working while they are in space, it is difficult to get up to fix them, so they are built to last and to be as self-sufficient as possible. Power is one resource that every satellite needs. While they could carry this in batteries, these are heavy and have a limited capacity. If a satellite can generate its own power while in space, it can function for longer. The most common way of doing this is with solar panels.

Some satellites have been sent to the outer solar system, where the energy received from the Sun is less. In cases like these, miniature nuclear reactors have been used as an alternative energy source.

The UK’s satellite speciality

Space is one of the harshest environments we have built equipment for. There is a high level of technical expertise needed to make sure that satellites can function properly in these conditions. The UK has a lot of this expertise and has developed a thriving industry around building satellites. The UK’s satellite industry has grown every year throughout the last decade and now employs 42,000 people.

Did you know?

The world’s first satellite was Sputnik 1, launched by the Soviet Union. It spent 3 months and 1400 orbits in space measuring temperature and pressure.