Expanding SBAS Service Area Toward the Southern Hemisphere

Takeyasu Sakai, Kazuaki Hoshinoo, and Ken Ito

Abstract:	The SBAS is an international standard system which provide integrity information, differential correction information, and ranging signal by broadcast from geostationary satellite. Japanese MSAS, one of operational SBAS, has served the aircraft flying in the Fukuoka FIR which includes the mainland of Japan and surrounding oceanic area since 2007. The geostationary satellites for MSAS, MTSAT-1R and MTSAT-2, broadcast SBAS signal by global beams. Thus, in fact, MSAS geostationary satellites broadcast SBAS signals to the Southern Hemisphere in addition to Fukuoka FIR, however their augmentation information is not valid there; The augmentation information of MSAS is generated by GMS (ground monitoring station) inside Japan with assumption that it is applied to users within the service area. In this paper, the authors consider the technical possibility of expanding MSAS service toward the Southern Hemisphere, i.e., Australia. Our goal is providing Enroute to NPA (non precision approach) navigation services over the whole of Australia and APV-I (approach with vertical guidance, called LPV in the US) service to major cities in the continent. Additional facilities and necessary modification for this purpose are considered while the message bandwidth are also evaluated. The MSAS has an MRS (monitor and ranging station) in Canberra, Australia, for orbit determination of MTSAT geostationary satellites, however it is not enough to generate augmentation information valid over the continent; the SBAS needs some network of monitoring stations distributed within the intended service area. It is necessary to settle, at least, 15 to 20 monitor stations over the continent to serve for Australian users. The message bandwidth is an issue for this expansion. While the amount of long-term and fast correction messages is not affected, the amount of the ionospheric correction information broadcast by the SBAS clearly increases when it expands the service area because the number of IGP (ionospheric grid point) to be broadcast is roughly proportional to the geographic area of augmented region. Our consideration on the message bandwidth concludes that the current specification with 250 bps data rate allows expansion of MSAS service area to the Southern Hemisphere. Two scenarios are tested by the software SBAS simulator developed by ENRI; Scenario A: Australia has its own MCS and MSAS works as just a transponder for Australian users; and Scenario B: A MCS serves both countries simultaneously by a single PRN signal. In these scenarios, all parameters except GMS configuration are set equally. The real SBAS message is generated and evaluated by using observations of Japanese GEONET and Australian CORS and it was shown that SBAS has capability to serve to both Hemispheres simultaneously with the reasonable performance.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	1377 - 1388
Cite this article:	Sakai, Takeyasu, Hoshinoo, Kazuaki, Ito, Ken, "Expanding SBAS Service Area Toward the Southern Hemisphere," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 1377-1388.
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