Long duration strapdown stellar-inertial navigation using satellite tracking

A strapdown stellar-inertial navigation system (INS) is currently being developed which can be used to correct for the gyro drift in an INS throughout a long-duration mission. The star sensor provides updates of the inertial angle error derived from stellar observations. However, since the star sensor updates are unable to correct for INS drifts due to accelerometer errors, the stellar inertial navigation solution accuracy degrades with time. A study has been performed on the number of visible satellites that can be tracked by the stellar-inertial system. The authors discuss the results of this study and include simulation results showing the performance improvement possible using both star and satellite observations to bound the system error growth. The results have shown that the combination of measurements can maintain the system error growth to within 700 ft over a long-duration mission.<>