The Inertial Reference Unit (IRU) used in NASA’s Orbiting Astronomical Observatory (OAO-C or Copernicus) uses three single degree of freedom, floated, rate-integrating gyros operated in binary, pulse-restrained
torque loops to provide an inertial attitude reference for the spacecraft’s altitude control system. Since 21 August 1972 when the spacecraft was launched, more than 15,000 hours of continuous and troublefree operation have been accumulated on the IRU. When prelaunch operation is included, the running times for the gyro wheels range between 17,000 and 22,000 hours.
The drift rates observed on these inertial grade gyros during the 1 1/2 year of in-orbit operation have remained within a band of 16 arcsec per hour peak-to-peak. When the effects of known disturbances are considered, the standard deviation of drift rate appears to approach one arcsec per hour (|
|Published in:||NAVIGATION, Journal of the Institute of Navigation, Volume 21, Number 4|
|Pages:||333 - 342|
|Cite this article:||Harris, R. A., "IN-ORBIT PERFORMANCE OF THE OAO INERTIAL REFERENCE UNIT", NAVIGATION, Journal of The Institute of Navigation, Vol. 21, No. 4, Winter 1974-1975, pp. 333-342.|
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