A positioning system is a mechanism for determining the location of an object in space. Technologies for this task exist ranging from worldwide coverage with meter accuracy to workspace coverage with sub-millimetre accuracy.
Interplanetary-radio communication system not only communicate with spacecraft, but are also used to determine their position. This can be done either using a transponder on-board a spacecraft that echoes a radio signal back, or using radar. Orientation information can be obtained using star trackers.
Global navigation satellite systems (GNSS) allow specialized radio receivers to determine their 3-D space position, as well as time, with an accuracy of 2–20 metres or tens of nanoseconds. Currently deployed systems use microwave signals that can only be received reliably outdoors and that cover most of Earth's surface, as well as near-Earth space.