S.I.D

Space Intruder Detector (S.I.D), as the name suggests, is a satellite designed to detect and report sightings of UFOs.

The satellite maintains an orbit around the Earth directly opposite the Moon, and at the same distance from Earth as the Moon. With Moonbase and SHADO control, S.I.D completes the entire tracking area around the Earth, so SHADO is able to keep a constant watch in any direction. Packed with computerised instrumentation, S.I.D possesses a programmed voice and scans the operations of all SHADO's craft on or above the Earth.