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Also of note is Japan's Quasi-Zenith Satellite System[0], which finished placing its 4 satellites in October 2017. These provide GPS coverage from near-vertica
by finnh 8y ago
Also of note is Japan's Quasi-Zenith Satellite System[0], which finished placing its 4 satellites in October 2017. These provide GPS coverage from near-vertical angles over Japan at all times, giving accurate location fixes despite Tokyo's deep urban canyons. The geosync orbits designed for this are pretty cool.
[0] https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System
- walrus01 8y agoInteresting to see they're using molniya orbits but for a very different purpose than the Russian telecom, military comms and broadcast satellites which most commonly use them.
- moftz 8y agoIt's not really that different of a purpose. You want at least one satellite visible in the sky, not on the horizon, nearly overhead. A highly elliptical geo tundra orbit gives you that overhead pass that a normal geostationary orbit can't give you. US Satellite radio (like Sirius) uses a tundra orbit with multiple satellites to cover the US and some parts of Canada and Mexico. You get max overhead time over the US with at least one satellite at all times so the connection is always good unless things on the ground interfere. Japan is doing the exact same thing as everyone else here.
- kevin_thibedeau 8y agoSirius XM is now geo only.
- moftz 8y agoMakes sense, those satellites are well past their scheduled lifespan.
- deepsun 8y agoIt's not Molniya orbits. Molniyas are highly elliptical.