Safran CORTEX CRT Quantum - Integration Time; Ranging Sequence

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 194
3.6.13.4.Integration Time
The minor tone duration is imposed by the satellite and is expressed as an integer M Epoch periods.
This configuration is programmable in the Cortex CRT (cf. parameter at offset 2 of the Ranging Unit Table
0x1034).
The actual integration time for ambiguity resolution is about (M-2) Epoch periods but the operation lasts for M
Epoch due to the fact the sequence is imposed by the satellite.
3.6.13.5.Ranging Sequence
Next figure illustrates the ranging measurement sequence:
2
4
6
1 7
IT = Integration Time
IT IT
N measurements on the major tone
One measurement every 250 ms
Major tone
Major tone
Minor tones
IT IT
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4
3
5
Figure 84: Ranging Sequence (Hybrid Ranging Standard)
There is a continuous transmission of a minor tones sequence along with the major tone.
 1. On reception of a ranging request from the Ranging Client, the RAU computes the tone definition
table (only the first time a ranging request is received for the current RAU configuration). Then, if the
computation is successful, the RAU continues processing otherwise returns an error code.
 2. Determination of the beginning of the sequence: the RAU waits for an entire minor tones sequence
and estimates the uplink epoch that corresponds to a new sequence. The beginning of the sequence
is therefore estimated with an uncertainty of one Epoch.
 3. Waiting for the beginning of the next minor tones sequence.
 4. Status Measurement Progress in the RAU monitoring table starts incrementing.
 5. Average phase measurement for the first minor tone, then for minor tones 2, 3, 4, 5 and 6.
 6. First phase measurement on the major tone and ambiguity solving. The RAU simultaneously
acquires the current time from the Time Code Reader for further time-tagging of the ranging
transaction response message.
 7. Status Measurement Progress is equal to 100. Phase and « distance » measurements are
returned to the Ranging Client(s) in a ranging transaction response message.