Research On Mars Probe Interplanetary Orbit Determination

China is developing"Phobos/YH"Mars Exploration Project in cooperation with Russia, for which orbit determination (OD) is an important component of the project and scientific experiment. When tracking data, force and measurement models are given, OD accuracy depends on statistical properties of the error sources and parameter observability. On one hand considering existence of many error sources in the Mars probe OD and reduction of their effects, elaborate understanding of their characters is necessary and much expert and special processing are needed. On the other hand in constraints of observability and resolvability, it is essential for analysis of different data processing resolutions. In this dissertation which is on the basis of simulation of Phobos-YH Mars exploration program, several problems in OD are investigated. Firstly, error budget calculation and sensitivity analysis are made for interplanetary OD. Secondly, a new filtering scheme originating from comprehensive adaptive filter is developed for solar radiation pressure model error compensation. Thirdly, a new method is proposed for angular momentum desaturation (AMD) detection during interplanetary cruise utilizing precise Doppler and ranging observable. Finally OD accuracy from different resolutions of YH-1 circum-Mars orbit are calculated and analyzed based on One-way Doppler and Differenced Doppler.The main contents and conclusions are as followed:1. A preliminary trajectory ranging from parking to circling phase is generated via STK/Astrogator. Then an advanced trajectory based on the preliminary one and complex force model is produced and corresponding observable is generated. Finally observability for tracking station is analized.2. Comparison on OD accuracies of two filter schemes is made using consider covariance analysis and treating Earth orientation parameters and media delays as considered parameters will not severely reduce OD accuracy. Then analysis is made to catalog the contribution of a particular error source or error source group to the overall estimation errors and to identify the major error contributors. Major error sources are derived including SRP model error, other NGA errors and measurement noise.3. The effect of mismodeling designed values of filter noise parameters while fixing their actual values is studied using information covariance analysis and applied to different data type combination cases. Results show that some error sources including measurement noise, a priori information of the Epoch orbit, NGA, SRP and pole motion parameters are more sensitive than others.4. The effect of mismodeling actual values of filter noise parameters while fixing their designed values is studied using information covariance analysis and applied to different data type combination cases. The major error source NGA and minor one UT1-UTC are illustrated. Results show that actual OD errors increase with deterioration of error sources as well as the sensitivity indes. In addition OD errors are more sensitive to major error sources. As a result the error source that appears highly sensitive must be treated carefully and accurate a priori statistical properties should be obtained.5. Effects of estimating SRP coefficients only are analyzed given model errors originating from satellites structure, attitude and material properties based on three data type combination. The result shows that filter divergence should occur and coefficients appears unreasonably in the cases where Range data exist. However in the Doppler plusΔDOR case and Doppler only case OD solution is acceptable even though with much less accurate radial position.6. Based on the comprehensive adaptive filter, a new OD filter strategy for Mars exploration interplanetary cruise is developed when major SRP model error exits. Considering insensitivity of Doppler andΔDOR observable to dynamical model errors, first a less precise orbit is obtained using these two data types as an external testing solution. Then state noise covariance matrices are estimated by the window method with range, Doppler andΔDOR data types to get the precise orbit. Application in YH interplanetary OD simulation shows that this new scheme can prevent the operational filter from divergence, provide more accurate position information of the orbit in the radial and along track directions as well as reduce labor on tuning stochastic parameters.7. A technique is proposed for Mars exploration interplanetary cruise AMD testing and its event time estimation. In addition effectiveness and capability of the method are further studied in different conditions. Simulation shows that the best timing estimation formal precision is as good as 10min. FinallyΔV due to AMD is estimated.8. The filter strategy utilizing One-way Doppler and differenced Doppler for YH circum Mars orbit and the corresponding OD accuracy are investigated. Technique possibility is calculated and analyzed. Also included in the work is preliminary analysis of TT&C network optimization and effects of frequency bias and drift on OD accuracy. Consequently an OD filter scheme is devised which can meet the need of required positioning accuracy of the project.