A platform errors estimation method of Doppler scatterometer based on residual Doppler shift

The velocity measurement error of the Doppler scatterometer is susceptible to the platform attitude, so the Doppler velocity measurement task puts forward high requirements for the platform attitude estimation accuracy. To achieve the velocity inversion accuracy of 5 cm/s, the slant range error should be less than 20 m, and the attitude angles should reach $1\times 10-3^{\circ}$. However, the existing attitude determination methods cannot achieve such high accuracy. Therefore, this paper presents a platform error estimation method based on radar echo signals. Firstly, a residual Doppler shift model was established through the geophysical model to describe the relationship between the residual Doppler shift and the slant range error and each attitude angle (roll, pitch, and yaw). Then, the optimal estimator method with high accuracy is used to calculate the estimated value of the Doppler centroid. Assuming that the Doppler estimation error between the estimated value of Doppler centroid and the theoretical value of Doppler centroid is the residual Doppler shift caused by the slant range error and attitude angles, the relationship equation between the residual Doppler shift and the slant range error and attitude angles can be established from the echo data in different azimuth angles. Finally, the least square method is used to solve several relational equations, and the estimated values of the slant range error and each attitude angle are obtained. The feasibility, estimation accuracy and robustness of this method are analyzed by simulation.