Talk:Quasi-Zenith Satellite System

Satellite animation for QZSS

QZSS animation

The animation of the QZSS satellites orbits seems to be not accurate. The orbits of the QZSS are Highly Elliptical Orbit, while the orbits in the animations are not (or I may be wrong in interpreting them of course). To have an elliptical orbit the earth should be drawn in one focus of the ellipse and the satellite speed should change depending on the orbit position. The orbits of the current animation seems to be circular orbits (earth in the center, constant speed). Any idea? --Claudev8 (talk) 07:28, 6 September 2012 (UTC)

Update: the problem is that the orbit of the QZSS satellites are *not* Highly Elliptical Orbit. Downloading the satellite almanac from http://qz-vision.jaxa.jp/USE/en/almanac it's possible to see tha the orbit is not highly elliptical: the eccentricity is approx 0.075 resulting is an orbit that is nearly circular. In conclusion the animation should be ok, but the article needs to be updated. --Claudev8 (talk) 09:01, 6 September 2012 (UTC)

Where else is this possible?

From the picture it looks like it is over Australia much of the time as well, is Australia involved in this project at all (I guess not)? Is this system going to be usable in Australia?

Well, after a quick bit of research I turned up the following links: http://www.location.net.in/magazine/2007/jan-feb/30_2.htm which seems to suggest that over Australia and much of China the GPS will be much improved (not just in Japan). http://pdf.aiaa.org/preview/CDReadyMICSSC04_940/PV2004_3203.pdf "Quasi-zenith satellite systems (QZSS), which consist of three or more satellites placed in geosynchronous orbits with identical inclinations of around 45 degrees, have been in the spotlight because of their ability to provide communication services at high elevation angles, both in Japan and Australia."

http://qzss.jaxa.jp/is-qzss/IS-QZSS_01_E.pdf (warning quite large) seems to suggest that Perth and Sydney (as well as Bangkok, Singapore and Seoul) are all targeted (~ page 23). Except that page 29 seems to imply that the coverage will be less than 50% for all of (and less than about 40% for most of) Australia. Except that on the same page it says that for most of the place (Oceania). "For the 3-satellite QZSS constellation, at least one QZS is available 100% of the time not only in Japan but in almost all parts of Southeast Asia and Oceania at an angle of elevation of 10° or more." I don't know what that means.

The following links might also be useful: http://www.nistep.go.jp/achiev/ftx/eng/stfc/stt016e/qr16pdf/STTqr1607.pdf

In conclusion, I think that the system will be usable in Australia, and much of the rest of Oceania and East Asia. I am however, not an expert, and don't understand most of this stuff. Justanothersock (talk) 18:04, 9 December 2008 (UTC)

This type of orbit is very different than almost any other satellite you might be familiar with, so take some time with the links to the orbit articles. Don't let the projection of the orbits confuse you; while near Australia the satellites are close to the Earth and moving at a fairly high speed and therefore not well positioned to offer a continuous signal there. The elliptical orbit lets them dwell over Japan at a high altitude for a stable amount of time. - Davandron | Talk 04:24, 12 December 2008 (UTC)

Moreover, to fully benefit of the service a converage of many ground stations is needed to generate the GNSS augmentation data. Since the system is operated by Japan, the ground stations will be likely placed in Japan and the GNSS augmentation signal will carry information related to the Japan area. In Australia(for example) you may be able to receive the signal(and use the ranging signal), but maybe you can't benefit by all the QZSS features. --Claudev8 (talk) 13:41, 5 September 2012 (UTC)

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3 satellites? 4? 7?

It looks like part of the article are still stuck at the original 3-satellite plan. Meanwhile Template:Future spaceflights lists satellites 5-7 for 2023 that don't appear in this article. If this is a future plan it should be added here. --mfb (talk) 02:52, 20 January 2018 (UTC)

Article out of date - QZSS is now fully operational

QZSS is now fully operational as a 4 satellite system http://qzss.go.jp/en/overview/notices/qzss_181101.html — Preceding unsigned comment added by 110.23.147.208 (talk) 06:58, 5 November 2018 (UTC)

Non-Primary Source Needed?

I'm curious about the "Non-Primary Source Needed" tag at the end of the "QZSS timekeeping and remote synchronization" section. The last two sentences of the section list papers on the topic and give references to them. The second reference has that tag.

I'm not clear how there could be a non-primary source in this case. What's written is simply the name of the paper and a reference link to it. Chris uvic (talk) 16:38, 23 September 2020 (UTC)