GEO NAV/CNAV-type Broadcast Ephemeris Fitting without Rotation of Inclination

• Main Authors: DU Lan, LIU Zejun, ZHOU Peiyuan, FANG Shanchuan, LIU Li, MA Gaofeng
• Format: Article
• Language: zho
• Published: Surveying and Mapping Press 2017-03-01
• Series: Acta Geodaetica et Cartographica Sinica
• Subjects: GEO satellites; broadcast ephemeris parameters; nonsingular orbital elements; perturbation; user range error
• Online Access: http://html.rhhz.net/CHXB/html/2017-3-297.htm

The GPS-type broadcast ephemerides are currently used by BDS constellation. However, a 5°-rotation added on the original orbital inclination is needed in the GEOs ephemeris parameters fitting algorithm as well as in the user satellite position computation because of the singularity due to small inclination. Besides, the phenomena of exceeding the given boundary happen occasionally for some ephemeris parameters of GEOs. In order to unify the user ephemerides algorithm for the hybrid constellation, a two-step GEO broadcast ephemerides fitting algorithm was analyzed based on the first class nonsingular orbital elements. After the investigation on the reason for the variations of some ephemeris parameters out of limited range, a reduced fitting parameter set was adopted by giving the underlying one or two parameters with fixed values. Fit simulations for 5 GEOs during both eclipsing and non-eclipsing periods show that the two-step fitting algorithm has considerable robustness to ensure the success rate and fitting accuracy. The mean fitting user range error of GEOs with 2 h for NAV and 3 h data set for CNAV are better than 3 mm. For specific fit arcs with the boundary-exceeding problem, it can be fully avoided by using the fitting algorithm with a reduced fitting parameter set. However, the fitting URE will increase to 2 cm.