Precise Orbit Determination For LEO Based On Single Frequency Measurement

Dual-frequency(DF) orbit determination technology based on GPS has been quite mature. However, when only single-frequency(SF) measurements are available, ionospheric delay which ranges from centimeters to meters, becomes a main error source. Therefore, how to eliminate the effect of ionosphere is so important in the SF orbit determination. This thesis comprises three aspects of work:1. Basic orbit determination theory based on SF GPS is introduced, including time system, coordinate system, the measurement of GPS signal, the pre-processing of SF measurement and reduced-dynamic algorithm.2. The ionosphere delay correction method based on ionosphere model is researched on. Firstly, we study how the ionosphere affects the GPS signal and the application of GIM. Secondly, aiming at the limitations of the application of scale factor in GIM, we propose a method which estimates the scale factor that is constrained by piecewise linear model based on the height of satellite, and then give the respective parameter estimation algorithm. At last, we calculate the orbit of GRACE A, GRACE B and CHAMP based on this method using the reduced-dynamic algorithm. The solutions show that these three satellites have 3D accuracy 0.786 m, 0.737 m, 0.822 m, respectively, which are improved by13.45%, 16.93%, 41.77%, respectively. The result shows this method can overcome the disadvantage of traditional method, and reflects the change of ionosphere in small scale.3. SF orbit determination based on GRAPHIC is studied. Firstly, we investigate GRAPHIC has the characteristics of both code and phase. Secondly, in order to detect small cycle slip, one residual editing method is introduced. At last, we use AC and GRAPHIC to solve the orbit of GRACE A, GRACE B and CHAMP using the reduced-dynamic algorithm. In the reduced-dynamic model, we optimize the choice of the model of conservative force for compensating the noise of measurement. The solution shows the 3D accuracy of the three satellites are 9cm, 9cm and 14.4cm, respectively. In comparison with the results of the method which doesn't correct ionospheric delay, the 3D accuracy have been improved by 83.9%, 82.2%and 78.25%, respectively.