10 Configuration and Status Monitoring
Step 3
Satellite Reception and Synchronization
Once the antenna and power supply have been connected, the reference clock is ready for operation.
After around two minutes of the system being switched on, the oscillator will have warmed up and thus achieved
the base precision required to receive satellite signals. If valid almanac and ephemeridal data are present in
the reference clock’s battery-backed memory and the receiver’s position has not changed since it was last on,
the system’s CPU will be able to calculate which satellites should currently be receivable.
In this case, only a single satellite needs to be received to enable the receiver to synchronize.
Warm Boot
If the location of the receiver has changed by several hundred miles since the last time the system was on, the
elevation and Doppler shift of the satellites will not match the calculated values. This will cause the system to
switch to "Warm Boot" mode, in which it will be systematically search for satellites to receive from.
The receiver can use the valid almanac data to detect the identification numbers of existing satellites. If
four satellites can be received, the receiver’s new position can be determined and the device will switch to
"Normal Operation"
mode.
Cold Boot
If there is no available almanac data (e.g., because the battery-backed memory has been wiped or corrupted),
the GPS reference clock will launch in "Cold Boot" mode, in which the receiver searches for a satellite and
reads the entire almanac. This process is completed in around 12 minutes, after which the system will switch
to "Warm Boot" mode.
IMS-GPS182
Date: June 16, 2022
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