Prelaunch Checkout of the Inertial Upper Stage Redundant IMU in the Magellan and Galileo Missions

Abstract

The Redundant Inertial Measurement Unit (RIMU) is used in the Redundant Inertial Navigation System (RINS) of the Inertial Upper Stage (IUS). Recent IUS missions of critical importance to the space community culminated in successful trajectory insertions of the Magellan and Galileo interplanetary spacecraft. The redundancy features of the strapdown RIMU, combined with a technique for on-pad calibration and sensor consistency checks, provide a comprehensive, self-contained performance-monitoring capability during on-pad, prelaunch checkout. This capability was exploited during launch holds, and recycles of both the Magellan and Galileo missions. The RIMU was maintained in its preliftoff gyrocompass mode of operation with no quiet-time restrictions for extended time periods, thereby allowing a rapid return to launch readiness.