Safran CORTEX CRT Quantum - Figure 81: 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
© Safran Data Systems
This document is the property of Safran Data Systems.
It cannot be duplicated or distributed without expressed written consent.
Page 180
Figure 81: Ranging Sequence (INMARSAT/LMCO Standards)
 1. RAU in idle state: mute output.
 2. On reception of a ranging request from the Ranging Client, the RAU computes the tone definition
tables (only the first time a ranging request is received for the current RAU configuration. Duration: < 3
seconds). Then, if the computation is successful the RAU starts transmitting the first tone (major tone or
19-kHz or 27.778-kHz sub-carrier phase-modulated by any of the four minor tones).
 3. 6 seconds later (tone set time), the RAU instantaneously performs the first phase measurement and
simultaneously acquires the current time from the Time Code Reader for further time-tagging of the
ranging transaction response message. Next measurements on the first tone take place every 100 ms.
 4. For the second, third and fourth tones, the process is similar.
 5. End of phase measurement on the fourth tone. Idle state.
The total duration of the ranging sequence depends on the measurement sampling ratio and the number of
measurements on each tone. Assuming 10 measurements per tone and a sampling ratio of 1 (all measurements
transmitted), the sequence duration (computation time for tone definition tables not included) is:
 1
st
tone set time 6 seconds
 Measurement on 1
st
tone 0.9 second
 2
nd
tone set time 6 seconds
 Measurement on 2
nd
tone 0.9 second
 3
rd
tone set time 6 seconds
 Measurement on 3
rd
tone 0.9 second
 4
th
tone set time 6 seconds
 Measurement on 4
th
tone 0.9 second
Total sequence duration 27.6 seconds
100 ms
1 2 3 4 5
TONE 1 TONE 2
6 seconds 6 seconds
TONE 4
6