Circular Orbit Patterns Providing Continuous Whole Earth Coverage

A study has been made of circular orbit patterns which ensure that every point on the earth's surface can always see at least one satellite (or two satellites for double coverage) above some minimum elevation angle. It is shown that five or six high altitude satellites can provide single coverage, and seven or nine satellites double coverage, at elevation angles which represent a significant improvement over previously published values; and a generalized approach to such coverage assessments is presented.