Tropospheric Bias Estimation Using GPS Radio Occultation Measurements of Bending Angles

Tropospheric biases in radar tracks are estimated using bending angle measurements, determined using GPS radio occultation (GPS-RO) techniques. Elevation bending angles are determined from excess Doppler shift, derived by differentiation of carrier phase measured by a GPS receiver on the radar. Radar and bending angle measurements are processed by an extended Kalman filter with position, velocity, and tropospheric bias states. Performance analysis shows that bias estimation reduces radar tracking errors, and it also improves radar covariance consistency. This work is the first known application of GPS-RO techniques to improve the track accuracy of a ground-based missile defense radar.