RADARSAT attitude estimates based on Doppler centroid of satellite imagery

An algorithm is developed for computation of the expected Doppler shift in the returned SAR signal. The Doppler shift is a function of the attitude of the satellite, range time and the position of the satellite in the orbit. The least squares error between the results of the algorithm and the measured Doppler centroid of an image yields the yaw and pitch of the satellite corresponding to the time of the image. Sixteen images, taken after a series of corrections to the attitude control system tables, are analyzed. The resulting yaw and pitch values were -0.15/spl deg//spl plusmn/0.05/spl deg/ and -0.06/spl deg//spl plusmn/0.12/spl deg/. The insensitivity of the calculated yaw and pitch values to small variations in the assumed roll of the satellite is demonstrated.