Where Do Satellites Get Their Power From?
Every machine needs energy to function and satellites are no exception. Satellites need electrical energy to serve their purpose of delivering important weather, climate and ocean data to Earth.
However, getting power out in space is trickier than it is on the ground. So what keeps the satellites running once they’re launched?
Power from the Sun
The Sun is the main energy source for satellites, which is why all satellites have solar panel arrays mounted on them. Each array contains thousands of small solar cells which are made of silicon – a material that allows sunlight to be turned into electrical current.
As you can see on the Jason satellite (above), solar arrays are quite large. They have to be big because only 20% of the light arriving from the Sun is actually converted into electricity. Each array generates 4kW of power, which is just about what it takes to power 2 kettles!
Even though solar arrays are rotating and always pointed towards the Sun, sometimes a satellite has to operate through eclipses, which means that there is no sunlight to provide energy.
Burning fuel to move the satellites
What is more, to keep the satellite in its orbit, it has to be moved every now and then. These movements, called manoeuvres, are commanded from the mission control centre. Once the command reaches the satellite, a manoeuvre is carried out by firing small reaction motors called thrusters. Thrusters are burning hydrazine fuel – a very toxic and flammable substance that is even capable of igniting on its own.
Metop satellites are launched with 300kg of fuel in their tanks, which is enough to maintain the orbit for up to 10 years. During the mission, some fuel has to be used to compensate for atmospheric drag, but most is used to maintain the orbit’s inclination which is being affected by the Moon. This requires the direction of travel to be adjusted by a few milli-degrees each year. Even though the change in direction is extremely small, these manoeuvres can require up to 20kg of fuel because the Metop satellites are travelling so fast – approximately 8.5 km/s!
Avoiding collisions in space
In some cases, satellites have to be moved to avoid collision with space debris. Space debris includes everything from screws and bolts to larger chunks of spacecraft. This risk is highest for the Metop satellites which are operating in Low Earth Orbit at around 820km where most of the debris is.
Currently, around 20,000 such space junk objects bigger than 10cm are tracked using radar, but due to the speeds involved, even impacts from much more common smaller pieces of debris could cause severe damage to or even destroy Metop.
In short, our satellites function with a combination of fuel for important manoeuvres, solar energy for everyday activities and batteries that provide power whenever the sun’s rays are not available. Click here to find more information about the satellite manoeuvres.