Correction technique for velocity and position error of inertial navigation system by celestial observations

residual sensor errors and misalignment of an inertial navigation system cause deviation from the true navigation solution. The navigation errors grow as function of time, sensor errors and vehicle dynamics. A celestial aided inertial navigation system (INS), carried on a space vehicle, has to rely on the independent INS output until the vehicle gets out of the dense atmospheric layer. The misalignment and gyro drift then can be corrected employing techniques for in-flight alignment by celestial observations. The accelerometer bias can be detected and compensated after the burn out point. Subsequent contribution to navigation error due to misalignment and sensor errors thus can be restricted. The accumulated velocity and position errors, however, cannot be directly determined from celestial observations and the knowledge of accelerometer bias. A technique for velocity and position error computation is presented. Simulations for strapdown inertial navigation system (SINS), mechanized in space stabilized reference frame, are carried out. Tremendous improvement in navigation accuracy is observed.