Study Of Spacecraft Formation Orbit Determination Using Spaceborne GPS

Spacecraft orbit determination is the key technology for flying and control. Due to the ability to provide relative economic, accurate, continuous position services, spaceborne GPS technology for spacecraft gradually becomes to be the research hotspot of orbit determination technology. In this paper, the spaceborne GPS technology applied in spacecraft formation orbit determination is choose as the research object. And the spaceborne GPS measurement data processing, the absolute orbit determination, the relative orbit determination of spacecraft formation based on spaceborne GPS are researched in this paper. The specific research work are as follows:Through the statistical analysis of GPS navigation satellite observations situation, propose that in order to increase the amount of measured data, which will participated in orbit determination calculation, by reducing the observation elevation angle. And in the same time improve the continuity of low orbit spacecraft Orbit Determination. Subsequently, as the lower elevation angle observations will lead to increased measurement error, the impact of measurement error on cycle slip detection is analyzed. On this basis, the cycle slip detection part of TurboEdit algorithm is modified. In the process of cycle slip judgment process, accordance with the quality of observable data the weighting factor is introduced. And two kinds of mathematical models are proposed to construct the weighting factors. This relates the judgment of cycle slip detection with the carrier phase measurement error and observation elevation angle. Thereby reducing the risk of misjudgment of justice cycle slip.In ambiguity solution process of spaceborne GPS carrier phase measurements, the LAMBDA algorithm is introduced in this paper. In the least squares estimation of LAMBDA method a weighting matrix is designed. The construction of weighting matrix is depened on the elevation angle of carrier phase measurement and the quality of measurement data. According the data quality to assign different weighting factor in ambiguity in estimation process, in order to reduce the relation between different ambiguity and reduce the estimation error.Considering that GPS system will provide three kind of frequencies carrier signal in future, in this paper the shortcoming of CAR three frequencies ambiguity solution algorithm is analyzed. Then a verification method to verify the results that given by CAR is proposed. This verification method combines both wide-lane and narrow–lane carrier phase techniques to verify the CAR results. After the verification, the revise method for the CAR ambiguity algorithm is also given. Mathematical analysis and discussion show that the test method is feasible. Finally, the whole flow of three frequencies carrier phase integer ambiguity resolution, verification and revise process is given.In the research on spacecraft absolute orbit determination based on spaceborne GPS, four kinds of spacecraft absolute orbit determination method, which are the kinematics least-square method, dynamics Kalman method, reduced dynamic least-square method and the reduced Kalman method, are analyzed and compared. In the reduced dynamics orbit determination method, a select method of relevant parameters for empirical acceleration is proposed. Through fully estimating the unmodeling error and measurement error in orbit determination process, the appropriate parameters of empirical acceleration are chosen. With the more accurate relevant parameters, the effect of unmodeling error and measurement error on absolute orbit determination is reduced. Then a simulation of the above method which is based on the GRACE formation measurement is given.In the research on the spacecraft formation relative orbit determination, base on the absolute orbit determination results, two kinds of spacecraft formation relative orbit determination method are designed in this paper. In the"relative orbit determination method based on C-W dynamics equation", proposed that comput the perturbation acceleration of C-W equation in advance according to the result of absolute orbit results. So that the relative dynamics equation is changed into a linear, which simplify the process of relative orbit determination calculations. In the"relative orbit determination method based on absolute orbit difference", the relative orbit is composed by the difference of absolute spacecraft orbit results. Thus avoids the application of C-W equation and provides a another way for spacecraft formation relative orbit determination. In order to improve the accuracy of estimation, the two relative orbit determination methods both use the spherical UKF as the filter.In order to take full advantage of double difference observation data in spaceborne GPS, in two kinds of relative orbit determination method proposed by this paper, choose both double difference carrier phase measurement combinations of the refer spacecraft to member spacecraft and the member spacecraft to member spacecraft as observation. So that, in relative orbit determination process, the quantity of observation data has been significantly increased, and this will improve the accuracy of the relative orbit determination.Finally, the federal filter technology is introduced to fuse the results of two relative orbit determination methods, in order to get the optimal relative orbit. Then the simulations on the above methods are given.