GALILEO - Understanding GPS: Principles and Applications - page 587

integrity information of GALILEO through the GALILEO navigation
signals;
• Interface to COSPAS/SARSAT for dissemination of SAR return-link
messages through the GALILEO navigation signals.
3. Interfaces for satellite command and control:
• Interface to the satellite/payload manufacturers of GALILEO for
onboard software maintenance or support in contingency operations;
• Interface to external satellite control centers for support to LEOP/IOT
or contingency special operations.
10.5.2.1 GALILEO GCS
The GCS will perform all functions related to command and control of the satellite
constellation:
1. Constellation management, dealing with all aspects of populating,
maintaining, and replenishing the GALILEO satellite constellation, which
include:
• Long- and medium-term mission planning to ensure global coverage
and continuity of the GALILEO signal in space;
• Maintenance of the overall GALILEO satellite constellation;
• Implementation of an adequate satellite replenishment strategy;
• Recovery from contingencies and satellite failures minimizing the effects
on the service provision.
2. Satellite control, dealing with all aspects of monitoring and controlling
individual satellites for routine platform and payload operations or any
unplanned critical operations in a contingency case, which include:
• Satellite TT&C;
• Scheduling of TT&C, ranging, or contingency access to individual
satellites using the global network of TT&C stations;
• Planning and execution of individual orbit maneuvers, platform
maintenance, and payload commands;
• Support for onboard software maintenance.
A TT&C station network will service the GALILEO satellite constellation. The
TT&C network is composed of five ground stations with 13-m antennas working in
the S-band and providing global coverage of the GALILEO constellation.
The design of the GCS is determined by the requirements for routine contacts
with all satellites of the GALILEO constellation, the amount of telemetry data to be
downloaded, the required number and volume of telecommands, and the capacity
of the TT&C network to support nonroutine and contingency operations. Table
10.10 summarizes those drivers.