A system and method for a group of artificial satellites. The artificial satellite is placed into an orbit in which an individual satellite orbits on an elliptical orbit so that at least one of the artificial satellites is always viewable within a pre-defined range of operational elevational angle in...http://www.google.de/patents/US6422516?utm_source=gb-gplus-sharePatent US6422516 - Artificial satellite with an orbit having a long staying time in a zenith direction, an orbit control method and a communication system therewith
