An American spy satellite which had been “lost” for 25 years has finally been rediscovered after decades off-radar in Earth’s orbit. The S73-7 probe had been launched in April 1974 as part of the US Air Force’s Space Test Program, and had been set to circle above our planet to help calibrate “remote sensing equipment” to monitor the ground below. S73-7, just over two feet wide and known as the Infra-Red Calibration Balloon, had been launched into space inside a larger satellite – the KH-9 Hexagon – from which it then decoupled once it passed outside the Earth’s atmosphere. The USAF’s plan had …