Research On Analysis And Correction Of Error Sources In Range And Doppler Tracking Data For Deep Space Vehicles

High accuracy tracking data are required in navigation for deep space vehicles. So it is of great important to study error sources of these tracking data in order to gain precise observables. This paper mainly discusses the subjects involved in preprocess of radiometric tracking data, including coordinates transformation between different space-time frames of reference on the basis of General Relativity, relativistic light-time delay, plasma light-time delay, and error source magnitude analysis for range and doppler data as well as the accuracy of the correction models and/or methods. The primary conclusions are as followed:1 On the basis of simulated light-time data in different areas of the Solar-system and with various path-length, the curves in the calculation shows how the relativistic light-time delay (RLT) within a distance of 2AU varies with R and L, where R is the closest approach radius from the Sun to the light path and L is the length of the path. The result indicates that RLT increases with L and against R. In the area where 0.2AU<P<2AU, the magnitude of the RLT term is of an order of several kilometres. And the residual is less than 4cm, which is small enough to be ignored.2. Simulation results reveal that in the region where the tracking system works properly, interplanetary plasma light-time delay varies from several decimeters to several hectometre, and produce an error about 10^-2～10^-4mm/s in velocity in the direction of line of sight. The paper makes a summary of all kinds of plasma density model available, and conclues that residuals of observables remain a high level even if the observables are corrected by the optimum model. If observables are revised by a model, the model coefficients are to be estimated altogether. Accuracy of the dual-frequency method is to the order of the measurement noises.3. On the basis of analytical and emulational results form this paper and its references, a summary of all error sources of range and Doppler data for deep space vehicles is made. Among these errors, the one due to frequency instability cannot be revised. As a result, it is necessary to use qualified atomic clocks both on board and the ground. With respect to errors due to time difference between TDB and TAI, decision on which terms must be retained and which ones could be ignored can be made on the basis of requirements for accuracy and calculating time. As to light-time delay due to electric particles (in ionosphere and plasma area), two methods can be made ues of. To correct the delays with a certain model needs parameter estimation, and accuracy of the dual-frequency method is of the same order as measurement noise.