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.
The Sun is the main source of providing energy for the satellites. There are solar panels on the satellites to get solar energy from the sun. The sun does provide solar energy and since it's the main source of energy for the satellites, that leaves you with your answer which is solar energy.
