This groups includes about 200 communication satellites ("comsats") scattered in synchronous orbits above the Earth's equator. ... 6 Earth radii (42,000 km or 26,000 miles), these satellite make one orbit per day, and therefore as the Earth turns, they always stay above the same ground station. ... Still another application is the 24-satellite network of the "Global Positioning System" (GPS), in circular orbits at distances of about 4.1 Earth radii (26,000 km or 16,000 miles). ...
... 29a. Satellite looking up . ... 29e. Explorers of distant space . Space Index . This groups includes about 200 communication satellites ("comsats") scattered in synchronous orbits above the Earth's equator. ... 6 Earth radii (42,000 km or 26,000 miles), these satellite make one orbit per day, ( sidereal day of 23 h 56 min--see here ) and therefore as the Earth turns, they always stay above the same ground station. ... Next Satellite Class: #29e Missions to Planets and to Distant Space . ...
... The mission will consist of a stationary lander and a surface rover. The mission has the primary objective of demonstrating the feasibility of low-cost landings on and exploration of the Martian surface. ... The spacecraft will be launched in December 1996 for an arrival on Mars in July 1997. The scientific objectives include atmospheric entry science, long-range and close-up surface imaging, with the general objective being to characterize the Martian environment for further exploration. ...