Safran CORTEX CRT Quantum - Doppler Compensation Process

COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
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Page 202
3.7.3. Doppler Compensation Process
The Doppler prediction table contains pairs of (Time Offset, Frequency Offset) describing a Doppler trajectory.
The time offsets can be non-linear. The SPS linearly interpolates the Doppler trajectory depending on the
interpolation step which can take four values: 1 s, 0.1 s, 0.01 s, and 0.001 s (synchronized by 1pps signal).
Once the execution date is reached by the IRIG-B reference, the hardware starts updating the NCO (every 160
µs, 16 µs, 1.6 µs, 0.16 µs) until the end of compensation process.
The next figure illustrates the Doppler compensation process:
NoData Wait InProgress NoDataOff OffInProgress NoData
RequestReception
FirstOffset
LastOffset
On On On
Off Off
Figure 85: Doppler Compensation Process
Four states describe the process:
 Off: the compensation is disabled.
 NoData: the compensation is enabled and waiting for a request.
 Wait: the request is received and accepted, the Cortex waits for the execution date to be reached.
 InProgress: the process is running.
During the execution of a table, if the Doppler compensation is disabled, the interpolation continues until the end
of compensation where the last offset applied is kept.