An optimal design of the broadcast ephemeris for LEO navigation augmentation systems

ABSTRACT

As the deployment of large Low Earth Orbiters (LEO) communication constellations, navigation from the LEO satellites becomes an emerging opportunity to enhance the existing satellite navigation systems. The LEO navigation augmentation (LEO-NA) systems require a centimeter to decimeter accuracy broadcast ephemeris to support high accuracy positioning applications. Thus, how to design the broadcast ephemeris becomes the key issue for the LEO-NA systems. In this paper, the temporal variation characteristics of the LEO orbit elements were analyzed via a spectrum analysis. A non-singular element set for orbit fitting was introduced to overcome the potential singularity problem of the LEO orbits. Based on the orbit characteristics, a few new parameters were introduced into the classical 16 parameter ephemeris set to improve the LEO orbit fitting accuracy. In order to identify the optimal parameter set, different parameter sets were tested and compared and the 21 parameters data set was recommended to make an optimal balance between the orbit accuracy and the bandwidth requirements. Considering the real-time broadcast ephemeris generation procedure, the performance of the LEO ephemeris based on the predicted orbit is also investigated. The performance of the proposed ephemeris set was evaluated with four in-orbit LEO satellites and the results indicate the proposed 21 parameter schemes improve the fitting accuracy by 87.4% subject to the 16 parameters scheme. The accuracy for the predicted LEO ephemeris is strongly dependent on the orbit altitude. For these LEO satellites operating higher than 500 km, 10 cm signal-in-space ranging error (SISRE) is achievable for over 20 min prediction.

KEYWORDS:

• LEO
• broadcast ephemeris
• orbit fitting
• leo navigation augmentation
• orbit prediction

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All the LEO orbit data used in this study are publicly accessible. The data can be downloaded at following addresses. GRACE-A:https://earth.esa.int/; SWARM-E:https://swarm-diss.eo.esa.int; HY-2A:https://cddis.nasa.gov/; JASON-2:https://urs.earthdata.nasa.gov/

Additional information

Funding

This study was supported by the National Natural Science Foundation of China [grant number 42074036] and the Fundamental Research Funds for the Central Universities.

Notes on contributors

Xueli Guo

Xueli Guo is a postgraduate student at Wuhan University. His main research interests are GNSS data processing and LEO orbit determination.

Lei Wang

Lei Wang is an associate research fellow in the State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University. He received a Ph.D. degree in Electronical Engineer and Computer Science from the Queensland University of Technology, Australia in 2015. His research interest includes LEO navigation augmentation, GNSS precise positioning and LEO orbit determination

Wenju Fu

Wenju Fu is a Postdoc researcher, His research interest includes GNSS data processing and LEO orbit determination

Yingbo Suo

Yingbo Suo is a Ph.D. student, his research interest including GNSS/INS integration and LEO orbit determination

Ruizhi Chen

Ruizhi Chen is a professor of State Key Laboratory of Surveying, Mapping and Remote Sensing Information Engineering, Wuhan University, and director of the laboratory. His main research interests include smart-phone ubiquitous positioning and satellite navigation and positioning.

Hongxing Sun

Hongxing Sun is an associate Professor of State Key Laboratory of Surveying, Mapping and Remote Sensing Information Engineering, Wuhan University, his research interest includes GNSS/INS integration.