Monday, August 02, 2010

Satellite Navigation & QZS "Michibiki"

Japan is set to launch a new navigation satellite called "Michibiki". Its also called a Quasi Zenith Satellite (QZS) system because, unlike the usual Global Positioning System (GPS) satellites, this one is to have an orbit similar to the geo-stationary satellites, which stay about 36,000kms away but appear to be stationary with reference to a point on the earth surface.

The question is - how is the QZS Michibiki different from other satellite navigation systems which are set to break the US dominance over the GPS market?

Russia is coming up with GLONASS; European Union's  Galileo system is be operational by 2014; China's Beidou system is expected to be usable by 2020, and India is expected to launch its IRNS system, starting 2011.

At present the Global Satellite Navigation Systems is dominated by NAVSTAR of the United States. Such systems use a constellation of 20-30 satellites to provide global coverage in such a way that, in theory, it would be possible to know your exact bearings using a hand-held Gobal Positioning System (GPS) device that picks signals from satellites located in the Middle Earth Orbit (MEO: 10-15,000km). GPS devices detect pulses from at least three of these GSNS satellites to triangulate any given location.

The problem with the American system is that access is not guaranteed in hostile situations. Also it seems to be less effective in mountainous terrain or inside "urban canyons", where it may be difficult to get direct signals from at least three satellites. So the advantage of having a NavSat permanently overhead in the geostationary orbit makes a lot of sense.

But one QZS-Michibiki by itself seems to be of limited use. Perhaps that is the reason why it is being promoted as something that can "enhance" existing NAVSTAR-GPS services available in Japan..

JAXA's Michibiki Page -

QZ Vision -  (countdown ongoing)

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