Evaluation of AIRS inertial measurement unit accuracy from rocket sled test data

A series of rocket sled tests was conducted at Holloman AFB, New Mexico in 1981 and 1982. The sled carried an advanced development phase advanced inertial reference sphere (AIRS) inertial measurement unit (IMU). The telemetered data from the IMU were used in conjunction with reference data from the HAFB space/time measurement system to evaluate the IMU performance. Evaluation programs were developed to correct the IMU data with the space/time data, and to compute trajectory comparisons. These trajectory comparisons were used as observables in a Kalman filter estimation technique to provide estimates of modeled IMU errors. The high quality sled test data provided estimates of azimuth alignment error. They also revealed an error in the system-level calibration of one of the accelerometer parameters. This paper describes the post-test data evaluation techniques which have been developed for AIRS sled testing. It also provides examples of AIRS versus space/time velocity comparisons and interpretations of their significance as indicators of IMU errors.