Regional Satellite Navigation by Using MSAS and QZSS

QZSS (Quasi-Zenith Satellite System) is a Japanese satellite navigation program with a regional service coverage. The orbits for QZS (quasi-zenith satellite) are 24-hour elliptic orbit inclined 43 degrees in order to broadcast radio signals from high elevation angle into urban canyons. The first QZSS satellite, QZS-1 "Michibiki" was successfully launched in 2010 and the technical verification has been conducted by several organizations. The original concept of QZSS consists of three or more satellites on so-called Quasi-Zenith orbit and optional geostationary satellites, so as to enable satellite positioning independent of GPS. The performance of such a constellation would be limited in comparison with GPS, however, this will work as the national minimum backup regarding unexpected outage of GPS. This paper describes feasibility of such a backup system and results of an initial verification activity using three navigation satellites, i.e., QZS-1 and some geostationary satellites currently available. It was confirmed that horizontal navigation can be provided but users would experience some high HDOP periods twice a day with this configuration.