The Prospero satellite, also known as the X-3,[2] was launched by the United Kingdom in 1971. It was designed to undertake a series of experiments to study the effects of space environment on communications satellites and remained operational until 1973, after which it was contacted annually for over twenty-five years.[3] Although Prospero was the first British satellite to have been launched successfully by a British rocket, the first British satellite placed in orbit was Ariel 1, launched in April 1962 on an American rocket.
Prospero has the COSPAR (NSSC ID) designation 1971-093A and the US Space Command satellite catalogue number 05580.