Space integrated GPS/INS (SIGI) navigation system for Space Shuttle

This paper consists of a description of the lessons learned and the results of the integration of Honeywell's space-capable Space Integrated GPS/INS (SIGI) navigation system into the Space Shuttle vehicle. The SIGI, as demonstrated during the Shuttle flight test missions, was fully operational during all Shuttle mission phases, ascent, on-orbit, entry, and landing. The SIGI provides three independent navigation solutions (Blended GPS/INS, GPS-Only, and INS-Only) for output at all times. The software upgrades for Space Shuttle include an improved gravity model and blended Kalman filter error states. The SIGI provides a cold start capability to perform an in-space initialization. The SIGI has flown on six Shuttle flight demonstration tests (DTO 700-15). This paper will discuss the performance of the SIGI operation during these flights. These flight test missions have provided the insight into required SIGI software upgrades to make the SIGI more compatible to the existing Shuttle features and interfaces. Flight tests of the SIGI have demonstrated the expected improved performance of an Integrated GPS/INS system as compared to the existing stand-alone GPS and IMU systems.