Analysis of Space-Borne GPS Data Quality and Evaluation of Precise Orbit Determination for COSMIC-2 Mission Based on Reduced Dynamic Method

Abstract

COSMIC-2 is a remote sensing satellite mission that mainly provides scientific data for weather forecasting, ionosphere, and climate research. High precise orbit is the basis for the application of remote sensing satellite data. In order to realize the precise orbit determination (POD) of COSMIC-2, we have assessed the quality of space-borne GPS observation in detail, including the utilization of GPS observations, cycle slip ratio (o/slps), multipath error, single-noise ratio (SNR) and ionospheric delay rate (IOD) of the data, realized the POD of COSMIC-2 with the reduced dynamic (RD) method, and evaluated the accuracy of the solved orbit by means of the carrier-phase residual, overlapping orbit comparison and the reference orbit comparison. The data quality assessments show that the data is less affected by the multipath effect, the utilization of the data is low, cycle slips occur frequently, and the carrier-phase data is often interrupted. The POD results indicate that the root mean square (RMS) values of the carrier-phase residuals of six COSMIC-2 satellites are between 6.0 mm and 7.5 mm, The mean RMS values of the overlapping orbit are better than 0.92 cm, 1.33 cm and 1.03 cm in the radial (R), tangential (T) and normal (N) directions respectively, and the mean RMS values of the six satellites in the 3D direction are between 1.38 cm and 1.75 cm. The mean RMS values in R, T and N directions orbit determination accuracy of the reference orbit comparison are better than 5.61 cm, 6.59 cm and 2.29 cm respectively, and the mean RMS values of the six satellites in the 3D direction are between 7.35 cm and 8.79 cm.

A New Exospheric Temperature Model Based on CHAMP and GRACE Measurements

“…Thermospheric density drag is the largest uncertainty in determining the orbits of low-orbit space objects. Empirical thermospheric density models, such as COSPAR International Reference Atmosphere, the Jacchia-class model, Drag Temperature Model and Mass Spectrometer-Incoherent Scatter (MSIS), are widely utilized and contribute greatly to the prediction of thermospheric mass density for low-orbit satellite operations and space debris movements [1][2][3][4][5][6][7][8]. However, the relative errors of these usual empirical models are non-negligible, and they are particularly poor under extremely lower solar activity and geomagnetic storms [9][10][11][12].…”