An internal computer system that regulates the flight control of a spacecraft or rocket. It senses the motions of the vehicle on its three axes and calculates the changes needed.
The Apollo 11 lunar module had both a primary guidance and navigation system and an abort guidance system as a back-up for an emergency return to lunar orbit.
The space shuttle's guidance system, during launch, ascent, re-entry, and landing, has four computers operating at the same time with a fifth as a back-up. Each computer can perform 325 000 operations a second.
Subjects: Astronomy and Astrophysics.