A Mitsubishi Heavy Industries H-IIA rocket placed the Michibiki 4 spacecraft into orbit yesterday. This is the latest element of Japan’s indigenous satellite navigation constellation. The Michibiki constellation, which means “guiding the way”, is also called QZS – quasi-zenith satellite – because the complementary orbits of the four spacecraft will ensure that there is always a satellite near the zenith (as long as you’re in the Eastern Hemisphere, anyway, and particularly near a band from Japan to Australia). They are all intended to operate at geosynchronous altitude, much higher than the GPS constellation, but at a significant inclination. Geostationary satellites orbit on the plane of the Earths’ equator, which allows them to appear fixed in the sky. Since these have an inclined orbit, they will trace a figure-8 pattern in the sky over the course of a day. This variation will give GPS receivers something to track. Yes, I did say GPS — Japan says this will be fully compatible with GPS signals. It will be particularly beneficial in the dense urban areas of Japan, where GPS struggles to be accurate due to all the buildings blocking satellite signals. With satellites that stand high in the sky all the time, it will be much easier to get enough signals for a fix.
This was H-IIA’s thirty-sixth launch.