Global Positioning System Reference
In-Depth Information
ernment and industry over who will assume responsibility for operation of the
deployed QZSS constellation and ground infrastructure has resulted in an
announcement by the government that the planned communications and broadcast-
ing features will be dropped, and only a positioning and navigation service will be
provided. With the potential for consumer market, it is doubtful that the govern-
ment will defend this new go-it-alone position without industry and without a com-
munication service. However, plans for an expanded constellation for
communications services as well as navigation under a follow-on project called the
Japanese Regional Advanced Navigation Satellite system, which looked well sup-
ported in mid-2003, may not be brought forward by the business sector [66, 78].
No signal design information or signal specifications have yet appeared.
11.3.10 System Coverage and Accuracy
Exactly what regions of the Far East beyond Japan will benefit from QZSS depends
critically on the choice of orbit inclination, eccentricity, and argument of perigee.
Sharing Japan's longitude, it is nearly certain Australia will enjoy some coverage,
though the coverage will not be symmetric above and below the equator, and the
satellites in view will not linger at the zenith over any particular Australian city.
Ultimately, system performance in Australia, as well as Taiwan and the coastal
regions of China, will depend on the implementation of supporting ground infra-
structure in those areas. One recent compendium on QZSS shows notional sites for
tracking facilities as well as satellite signal monitoring in Bangkok, Hawaii,
Tsukuba (Tokyo), Okinawa, and Australia. These sites are under consideration in
simulations of system performance [72].
11.3.11 Future Development
It is not certain whether the QZSS satellites will provide an independent, GPS-like
ranging signal from the outset, but this has been a feature desired as a measure
enhancing the number of pseudoranging satellites available, as well as protection
against a feared but never occurring GPS outage. In addition to providing correc-
tions to GPS for accuracy, a likely next step that has been mentioned is to follow
developments under GPS III and provide similar corrections for the new signals. It is
likely that a similar service will be provided for current and future GLONASS sig-
nals, as well as GALILEO signals when the program comes into service around the
same time as QZSS itself (2008 and beyond).
After resolution of the impasse between government and industry on who will
become the operator of the deployed QZSS constellation, it is possible that interest
will be renewed in the Japanese Regional Advanced Navigation Satellite concept or
some measure like it. Details provided in public forum by the corporate interests
involved reflect careful consideration to one possible enhancement to QZSS, but
draw from proprietary research and development. These may change with ongoing
alterations in the final QZSS configuration and are outside the scope of this brief
review of the QZSS program.
 
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