Results of fusion of LRI based attitude data in the attitude Kalman filter

Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) carries the Laser Ranging Interferometer (LRI) as a technology demonstrator that measures the inter-satellite range with nanometer precision. For the precise laser beam pointing, LRI uses the beam steering method where the fast steering mirror is actuated to correct for the misalignment between the incoming and outgoing laser beams. From the fast steering mirror commands, we can compute the inter-satellite pitch and yaw angles. These angles are provided as LSM1B product and represent spacecraft's relative orientation with respect to line-of-sight (LOS). The SCA1B data, which is computed by combining the data of three star cameras and IMU in the Kalman filter, represents the absolute orientation of the spacecrafts. Currently, this SCA1B product is used in the gravity field determination.  

Here we present first results of a new attitude product which is computed by the combination of fast steering mirror data with the star cameras and IMU in the attitude kalman filter.  We also present the impact of this new combined attitude data on the gravity field solutions.