Implicit and Explicit Spacecraft Gyro Calibration

This paper presents a comparison between two approaches to sensor dibration. A c c o r d i to one approach, cnlled explicit, an estimator compares the sensor readiags to reference rendings, auad uses the difference between the two to estimate the calibration parameters. Accordii to the other approach, called implicit, the sensor error is integrated to form a different entity, which is then compared with a reference quantity of this entity, and the calibration parameters are inferred from the difference. In particular this paper presents the comparison between these approaches when applied to in-flight spacecraft gyro calibration. Reference spacecraft rate is needed for gyro calibration when using the explicit approach; however, such reference rates are not readily available for in-flight &ration. Therefore the calibration parameter-estimator is expanded to include the estimation of that reference rate, which is based on attitude measurements in the form of attitudequaternion. A comparison between the two approaches is made using simulated data. It is concluded that the performances of the two approaches are basically comparable. Sensitivity tests indicate that the explicit fdter results are essentially insensitive to variations in given spacecraft dynamics model paramders.