COMPONENT MAINTENANCE MANUAL
C17004
34-57-96
Page 1
COPYRIGHT
SEXTANT Avionique 1995
c
DESCRIPTION AND OPERATION
1.
General
A. Presentation
The Receiver Processor Unit (RPU) is built into the GPS (Global Positioning
System) navigation system NSS100S-1 (Navstar Sensor System type 100-1 SPS).
It can operate with an active or passive antenna (ACU), and with a preampli-
fier (PAU); these three units make up the user segment.
The antenna (ACU) picks up signals transmitted by various visible satellites
(as many as 8). These signals are amplified by the preamplifier (PAU) and
sent to the Receiver Processor Unit (RPU).
This RPU simultaneously analyzes and processes the signals transmitted by
the satellites (maximum of 8), in order to calculate a position-fixing so-
lution expressed in time and in three dimensions; after processing the data
contained in the satellite signals, the RPU calculates and transmits the air-
craft position, speed and time parameters.
B. Main Functions
- Acquisition in C/A code (Coarse Acquisition code) and tracking of signals
transmitted by satellites in the parallel mode over 8 channels (using
L1/L2 receive frequencies).
- Measurement of pseudo-distances and pseudo-speeds that correspond to the
satellites used.
- Fixing and maintenance of aircraft position and geographic speed based on
GPS measurements; position determination is based on the SPS system (Stan-
dard Positioning Service).
- Determination of GPS and UTC (Universal Time Coordinated).
- Taking into account parameters available on the input/output interfaces
and use of these parameters to improve performance (jamming resistance,
aircraft dynamic resistance, acquisition time...), depending on the
configuration.
- Self-test of GPS equipment functions and characterization of the quality
of information provided concerning position, speed and time.
This characterization includes detection of operational anomalies in the
space segment, whenever possible (particularly when 5 or more satellites can
be used).
- Demodulation of navigation messages transmitted by all satellites tracked,
management and permanent memory storage of the GPS constellation almanac.
- Maintenance of GPS time, equipment switched off for easier initialization.
OCT 16/95
The document reference is online, please check the correspondence between the online documentation and the printed version.