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3.6. Range Measurement
General
3.6.1.
The unit in charge of range measurement is the Ranging Unit (RAU). The RAU is a very precise phase-meter. It
measures the instantaneous phase-difference between the internally-generated tone and the same tone echo-
returned by the spacecraft. These measurements are performed at different frequencies, allowing to calculate a
propagation time and consequently a distance. Ambiguity solving (ESA, ESA-like and USB tone standards, ESA
code standard) is by the minor tones or PN code while the measurement accuracy is determined by the major
tone. Minor tones are derived from the major tone by division. The RAU supplies phase measurements as well
as two-way « distance » values expressed in nanoseconds.
3.6.1.1. Supported Standards
The RAU supports all types of tone standards, with tone frequencies in the range 2 Hz - 500 kHz
ESA tone standard (compliant to ESA TTC-A-04 standard, Issue 1, July 1980)
ESA-like and USB tone standards (programmable frequencies and tone sequence)
INMARSAT and LMCO tone standards
ESA code standard
Continuous mode for the ESA tone, ESA-like and USB standards
PN Codes (CRT eXplorer)
The RAU supports also measurements in Hybrid Ranging: uplink is MTC2: PCM/SRRC-UQPSK while downlink
consists in ranging tones that modulates carrier in PM.
3.6.1.2. Ranging ports
Two ranging ports are used for ranging data transfer to and from the Ranging Clients: RNG & MEAS. On
reception of a ranging request on port RNG, the CORTEX CRT Quantum returns a ranging primary transaction
response showing acceptance or rejection of the request. On completion (or premature termination in case of
anomaly) of the ranging sequence, the CORTEX CRT Quantum transmits simultaneously a ranging secondary
transaction response on port RNG to indicate the ranging sequence is terminated and a ranging transaction
response containing the measurement data on port MEAS. For a detailed description of the ranging messages,
see Annex 1, Section 2.7. Simultaneous connection of several Ranging Clients to port MEAS is accepted. Only
one Ranging Client can open a connection to port RNG.
3.6.1.3. "Local" Ranging Client
Using the Cortex MCS software, range measurement can also be initiated. Phase measurements from the
Ranging Unit are displayed in aggregated form (minimum, maximum, average and standard deviation values on
each tone) as well as a two-way propagation delay (in nanoseconds) and a one-way distance (in meters) for the
standards supporting ambiguity solving (ESA, ESA-like and USB tone standards, ESA code standard). Should
the ranging process fail (hardware failure, open loop, etc...), data are not displayed at the front panel.
© 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.
Safran Data Systems
.
Ref.
DTU 100042
Is.Rev.
5.17
Date:
Dec.
03, 2021Sept. 30, 2021
Page 148
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