PURPOSE: To enable communication of high quality and position measurement having no vagueness at any place on the earth by arranging ≥1 communication satellite each on a stationary track on the equator and ≥1 day-period track slanting to the equator surface.

CONSTITUTION: The day period tracks 3 and 4 which slant at, for example, +60° and -60° to the equator surface are set in addition to the stationary track 2 on the equator of the earth 1, and six communication satellites S1WS6, Y1WY6, and X1WX6 are arranged on those tracks in proper correlation. Then at least three communication satellites can easily be tracked and acquired within a 90° visual field at any high-elevation position on the earth including an equator area and a polar region. Therefore, not only the communication, but also the position measurement are performed without any vagueness. At this time, those three satellites and a ground state are not on the same plane, so there is not any problem of vagueness.