Research on an Observations Weighing Method for Onboard GPS Zero-Differential Kinematic Orbit Determination

Onboard GPS zero-differential kinematic orbit determination is sensitive to the observation quality.The GPS phase noise is much less than the code noise.If both the observations are equally weighed,the parameter solution performance of the highly precise phase will be decreased.However,the phase observations have ambiguity,using phase observations signally will make the structure of parameter estimation unstable.And the code noise has significant correlation with receiving antenna elevation.The GPS observation quality is analyzed.Combining the analyzed results with the principle of zero-differential kinematic orbit determination based on code and phase,a reasonable weighing method is proposed,and the precision and stability of onboard GPS zero-differential kinematic orbit determination is improved.Observations on the CHAMP satellite for one week are tested.The zero-differential kinematic orbit determination results are compared with the GFZ science orbit.The RMSs(root of mean square) in the R,T and N components are 20cm,12cm and 13cm,and the RMS in the three-dimension is 27cm.The precision comparison of several different weighing methods for orbit determination shows that the proposed weighing method is efficient.