"NASA's Mars Reconnaissance Orbiter is switching from one motion-sensing device to a duplicate unit onboard.
... The spacecraft has two identical copies of this motion-sensing device, called IMU-1 and IMU-2. Either of them can be used with either of the spacecraft's redundant main computers. Each contains three gyroscopes and three accelerometers.
"The reason we're doing this is that one of the gyroscopes on IMU-1 is approaching its end of life, so we want to swap to our redundant unit early enough that we still have some useful life preserved in the first unit," said Mars Reconnaissance Orbiter Mission Manager Reid Thomas of NASA's Jet Propulsion Laboratory, Pasadena, Calif."
Marc's note: An apparent minor servicing for MRO which has been on-duty for seven years and appears to be still be going strong.