Safran CORTEX CRT Quantum User Manual page 264


1. On reception of a ranging request from the Ranging Client, the RAU computes the tone and codes
definition tables. Then, if the computation is successful, the RAU starts transmitting the tone. Status
Measurement Progress in the RAU monitoring table starts incrementing.

2. Ta seconds later, transmission of code 2 (T-second set time).

3. Correlation process for the first code. The duration (parameter Integration Time) is programmable
from 250 ms to 2500 ms.
Steps 2 and 3 are repeated for codes 4 and 6.

4. Transmission of code 8.

5. Correlation process for code 8. The tone is then transmitted during Ts seconds (time necessary for the
PLL to stabilize).

6. First phase measurement on the 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 Measurement Client(s) in a ranging transaction response message.
Phase measurements on the tone are performed at regular time interval (One measurement every 250 ms).
These measurements are corrected as described in § 3.6.3.4. For each measurement on the tone is calculated a
« distance » in nanoseconds. The calculation takes into account (ambiguity solving) phase drift due to spacecraft
motion during tone transmission.
The total duration of the ranging sequence depends on six factors:

the tone frequency,

the measurement sampling ratio,

the integration time,

the number of measurements on the tone,

the code length,

the loop bandwidth.
Assuming that these parameters are: 300 kHz (tone frequency), 1 (no under-sampling), 1000 ms (integration
time), 10 measurements on the tone, 7 (code length. Transmitted codes = 2, 4, 6, 8) and 1 Hz (loop bandwidth),
the sequence duration is (the time to compute the tone definition tables is not included):

Pre-transmission of the tone

Codes 2, 4, 6 & 8 (set time + integration)

Transmission of the pure tone

10 measurements on the tone (0.25 x 9)
Total sequence duration
© Safran Data Systems
COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
This document is the property of
It cannot be duplicated or distributed without expressed written consent.
: 2.01 s
: 4.05 s
: 4.01 s
: 2.25 s
: 12.32 seconds
Safran Data Systems
.
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
Page 184