Editing Mars Express (section)

=== Attitude control - avionics ===
Attitude control (3-axis stabilization) is achieved using two 3-axis inertial measurement units, a set of two [[star camera]]s and two [[Sun sensor]]s, [[gyroscope]]s, [[accelerometer]]s, and four 12&nbsp;N·m·s [[reaction wheel]]s. Pointing accuracy is 0.04 degree with respect to the inertial reference frame and 0.8 degree with respect to the Mars orbital frame. Three on-board systems help ''Mars Express'' maintain a very precise pointing accuracy, which is essential to allow the spacecraft to use some of the science instruments.