NavCom SF-3050 Rev.B - Manual (Page 153)

SF-3050 User Guide – Rev B
StarFire in which dual-frequency ionospheric
measurements are available at both the reference
receivers and the user receivers. It is the use of dual-
frequency receivers at both the reference stations
and the user equipment together with the advanced
processing algorithms, which makes the exceptional
accuracy of the StarFire system possible.
Creating the corrections is just the first part. From our
two processing centers, the differential corrections
are then sent to the Land Earth Station (LES) for
uplink to L-Band communications satellites. The
uplink sites for the network are equipped with
NavCom-built modulation equipment, which
interfaces to the satellite system transmitter and
uplinks the correction data stream to the satellite that
broadcasts it over the coverage area. Each L-Band
satellite covers more than a third of the earth.
Users equipped with a StarFire precision GPS
receiver actually have two receivers in a single
package, a GPS receiver and an L-Band
communications receiver, both designed by NavCom
for this system. The GPS receiver tracks all the
satellites in view and makes pseudorange
measurements to the GPS satellites. Simultaneously,
the L-Band receiver receives the correction
messages broadcast via the L-Band satellite. When
the corrections are applied to the GPS
measurements, a position measurement of
unprecedented real time accuracy is produced.
Reliability
The entire system meets or exceeds a target
availability of 99.99%. To achieve this, every part of
the infrastructure has a built-in back-up system.
All the reference stations are built with duplicate
receivers, processors and communication interfaces,
which switch automatically or in response to a remote
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