The Quasi-Zenith Satellite System (QZSS) has been developed by Japan as a regional navigation satellite system covering Japanese territory and the surrounding region. The most distinguished property of the QZSS is broadcast of radiosignals from a high elevation angle to users, which improves availability of position fixes even in urban canyons and mountainous area. It is, however, a potential problem that a fail of QZSS satellite degrades this property largely because the QZSS consists of the relatively small number of satellites. The author investigated a recovery method from such a situation by relocation of satellites adjacent to the failed satellite. According to the computational results for the constellations of three to five satellites, the minimum elevation angle of the system could be improved by the relocation by about 20 degrees with change of orbital planes and by 6 to 10 degrees even if orbital planes are not changed.
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