| There currently are 24 operational
| |
| | lifespan. The GPS satellites have been
|
| satellites as part of the GPS satellite
| |
| | designed to provide a lifespan of ~8
|
| constellation, that orbit the earth with
| |
| | years. New satellites are being launched
|
| a orbital radius of ~16,000 miles (from
| |
| | to space at regular intervals of time to
|
| the center of the earth). The satellite
| |
| | make up for satellites that have lived
|
| orbits are spaced out in 6 orbital planes
| |
| | out their lifespan.
|
| (orbital plane is the plane surface
| |
| | When the satellites are launched into
|
| formed by the path traced by the orbit of
| |
| | space, they are inserted to
|
| the satellite - it is nearly circular).
| |
| | pre-calculated positions in their orbital
|
| The six orbital planes are separated by
| |
| | planes. The pre-calculations ascertain
|
| an angle of 60 degrees. Refer to the
| |
| | that a GPS receiver located anywhere on
|
| constellation figure below. Four to six
| |
| | earth and at all times, can receive
|
| satellites occupy each orbital plane.
| |
| | signals from at least four satellites.
|
| In addition to the 24 operational
| |
| | This is required because earth blocks the
|
| satellites, there currently are 6
| |
| | GPS signals from passing through it. For
|
| satellites in orbit that are maintained
| |
| | a GPS receiver to be able to receive a
|
| as spares, should any of the 24
| |
| | signal from a satellite, the straight
|
| operational satellites malfunction. The
| |
| | line-of-sight line should not have any
|
| six spare satellites are kept operational
| |
| | obstructions in between. Since the
|
| for users to receive signals from them
| |
| | satellites are flying around the earth,
|
| just like from the 24 satellites.
| |
| | not all satellites are visible to a GPS
|
| However, the U.S. Government does not
| |
| | receiver located somewhere on earth.
|
| guarantee their availability at all
| |
| | Thus, though there are 30 operational
|
| times.
| |
| | satellites, not all of them can be
|
| Remember that the GPS satellites are
| |
| | visible at a location on earth, at any
|
| being launched since 1974. Satellites
| |
| | given time.
|
| like everything else have limited
| |
| |
|
