Attitude Control

The subsystem that determines and controls which way a spacecraft points — sensing its orientation with star trackers and gyroscopes, and turning it with reaction wheels or thrusters.

A spinning gyroscope whose axis is tilted to produce large control torques efficiently — used on big, agile spacecraft such as the International Space Station and Earth-imaging satellites.

A spinning flywheel that a spacecraft speeds up or slows down to rotate itself, by conservation of angular momentum, without using any propellant — the workhorse of precise pointing.