The space
segment includes the satellites and the Delta rockets
that launch the satellites from Cape Canaveral, in
Florida. GPS satellites fly in circular orbits at
an altitude of 10,900 nautical miles (20,200 km) and
with a period of 12 hours. The orbits are tilted to
the earth's equator by 55 degrees to ensure coverage
of polar regions. Powered by solar cells, the satellites
continuously orient themselves to point their solar
panels toward the sun and their antenna toward the
earth. Each of the 24 satellites, positioned in 6
orbital planes, circles the earth twice a day.
The satellites are
composed of:
 Solar
Panels. Each satellite is equipped with solar
array panels. These panels capture energy from the
sun, which provides power for the satellite throughout
its life.
External
components such as antennas. The exterior of
the GPS satellite has a variety of antennas. The signals
generated by the radio transmitter are sent to GPS
receivers via the L-band antennas. Another component
is the radio transmitter, which generates the signal.
Each of the 24 satellites transmits its own unique
code in the signal.
Internal
components such as
atomic clocks and radio transmitters. Each satellite
contains four atomic clocks. These clocks are accurate
to a few billionths of a second (or nanosecond). An
accuracy of 1/100th of a second in the atomic clock
would translate into a difference of 1,860 miles to
the GPS receiver.
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User Segment: Aviation
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