Orbital representations for the next generation of satellite-based augmentation systems

Abstract

The landscape of the Global Navigation Satellite System (GNSS) is changing. New constellations are coming online, and a diversity of new signals are coming to the user space. Multi-frequency adds a means for ionospheric correction as well as robustness to jamming. Multi-constellation gives rise to better geometry and robustness to satellite failures. Systems which require a high degree of safety such as aviation require Satellite-Based Augmentation Systems (SBAS) to be used in conjunction with GNSS. As such, SBAS standards must be modernized to reflect the evolving GNSS environment. SBAS will deliver additional service on a new frequency at L5, giving the ideal opportunity to modernize the SBAS Minimum Operational Performance Standards (MOPS). Geostationary (GEO) satellites currently comprise the space segment of SBAS. However, GEOs remain at the equator limiting their visibility at the Poles. As activity in the Arctic is increasing, SBAS service in this region is of utmost importance to ensure safety. As such, it is desired that the next-generation L5 MOPS allow for orbit classes other than GEO. Orbital diversity for the delivery of SBAS corrections will allow for better visibility of this service on all places on earth. Here, we discuss the design and qualification of the L5 MOPS orbit messages, namely the ephemeris and almanac. These will support a multitude of orbit classes including all of those used today by both GNSS and SBAS.