Japan: Michibiki, Japan’s first navigation satellite, has entered its quasi-zenith orbit, the country’s space agency announced. The orbit stretches from a low point of 20,268 miles to a high point of 24,202 miles.
The quasi-zenith orbit, designed to maximise Michibiki’s coverage of Japan, has an average altitude equal to the distance of geosynchronous satellites from Earth. Its longitude is locked in at 135 degrees east longitude. The satellite has three more months of technology tests and commissioning before it enters service.
Projected against Earth’s surface, Michibiki’s ground track charts an asymmetric figure-eight pattern stretching from Japan to Australia as it alternates north and south of the equator.
Michibiki will be near-zenith, or almost straight up, in the Japanese sky for about eight hours each day. If launched, two follow-on satellites would permit continuous coverage of Japan.
Japan’s satellite navigation programme aims to augment signals from the GPS. Although there are 30 operational GPS spacecraft, only a small fraction of the fleet is visible from a single point on Earth at one time. A navigation terminal on the ground needs four GPS satellites to compute the user’s position, elevation and local time, but skyscrapers and mountains in Japan often block line-of-sight signals from spacecraft low in the sky.
Japan hopes to solve this problem by launching at least three satellites strategically positioned high in the sky over the country, where their signals will not be impeded by man-made or natural terrain.
Source: Spaceflight Now