Prelaunch Checkout of the IUS Redundant IMU in the Magellan and Galileo Missions

Robert A. Baum, Gerald E. S. Morrison, J. Kerry Hoskins

Abstract:	The Redundant Inertial Measurement Unit (RIMU) is used in the Redundant Inertial Navigation System @INS) of the Inertial Upper Stage (IUS). The IUS was developed for use as an upper stage on the National Aeronautics and Space Administration (NASA) Space Shuttle vehicle and the United States Air Force (USAF) Titan space booster. The strapdown RIMU contains five gyros and five accelerometers, and electronics, arranged in a redundant configuration such that no single component failure compromises system inertial performance. Failure Detection and Isolation (FDI) algorithms in the navigation computers automatically eliminate a failed sensor’s data from the navigation computations, and the mission navigation function continues on uninterrupted. Recent IUS missions of critical importance to the space community culminated in successful trajectory insertions of the Magellan and Galileo interplanetary spacecraft. IUS deployment in low earth or- bit was accomplished by the Space Shuttle Atlantis in each of these missions. The redundancy features of the strapdown RIMU, combined with a unique technique for on-pad calibration and sensor consistency checks, provide a comprehensive, self-contained performance monitoring capability during on-pad, pre-launch checkout. This capability was exploited during launch holds, and recycles of both the Magellan and Galileo missions. The RIMU was maintained in its pre-liftoff gyrocompass mode of operation with no quiet-time restrictions for extended time periods, thereby allowing a rapid return to launch readiness.
Published in:	Proceedings of the 46th Annual Meeting of The Institute of Navigation (1990) June 26 - 28, 1990 Atlantic City, NJ
Pages:	201 - 207
Cite this article:	Baum, Robert A., Morrison, Gerald E. S., Hoskins, J. Kerry, "Prelaunch Checkout of the IUS Redundant IMU in the Magellan and Galileo Missions," Proceedings of the 46th Annual Meeting of The Institute of Navigation (1990), Atlantic City, NJ, June 1990, pp. 201-207.
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