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Guidance, Navigation, and Control |
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Using three redundant pairs of sensors, the guidance, navigation
and control subsystem determines the spacecraft's orientation, or
"attitude." A sun sensor is used to detect the position of
the sun as a backup to the star camera. A star camera is used to look
at star fields. Between star camera updates, a device called the
inertial measurement unit collects information on spacecraft orientation.
This system also includes the reaction wheels, gyro-like devices
used along with thrusters to control the spacecraft's orientation. Like
most spacecraft, Odyssey's orientation is held fixed in relation to space
("three-axis stabilized") as opposed to being stabilized via
spinning. There are a total of four reaction wheels, with three used for
primary control and one as a backup.
The guidance, navigation and control subsystem weighs 23.4
kilograms (51.6 pounds).
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