(Opposite) NASA's new Tracking and
Data Relay Satellite (TDRS), top right, serves as an
orbit-to-ground-to-orbit communications link for Shuttle /Spacelab,
far below at right, as well as for other low-altitude satellites such
as the Landsat Earth observation satellite, center. Another
high-altitude communications satellite, top left, acts as a relay
between the TDRSS' ground stations (antennas at bottom). The
four-satellite Global Positioning System is shown in red. The U.S.
Space Telescope, right center, to be launched in 1985, is shown also
using the TDRSS.
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