Preliminary Design of the Galileo Mission Support Facility (MSF)

M. Sánchez-Gestido, A.Ramírez-Jiménez, F. Bertrand, A.I. Mediavilla, O. Bellido-Tirado and P.Falconio

Abstract:	The primary objective of the Galileo Mission Support Facility (MSF) is to provide an off-line reference orbit determination process to fine-tune the Galileo OD&TS real-time computations, and a verification capability for configuration and calibration parameters required in the Navigation chain by the OSPF (Orbitography and Synchronization Processing Facility) and in the Integrity chain by the IPF (Integrity Processing Facility). Several MSF performance requirements, in particular those related with integrity requirements, limit the risk of generating misleading/incorrect information at the output of the MSF. Safety analyses concluded that the functionality associated with the Navigation chain has to be developed in DAL”C” and that the functionality associated with the Integrity chain has to be developed in DAL”B”, according to the Galileo SW Standards [RD.1], both of them, posing stringent demands in terms of implementation, testing and in the overall verification & validation process. The provision of these calibration and configuration parameters, along with their associated criticality in the system and the required DAL, identifies the MSF as a key facility within the Galileo Ground Mission Segment (GMS). The MSF comprises the following components: .. Common Services Function (CSF) is an “interface and storage” component in charge of providing a physical interface between the MSF and the rest of Elements in the Galileo Control Center (GCCs) via an Ethernet connection. The CSF centralizes all local M&C capabilities of the MSF components by means of an adequate HMI, and also provides MSF status to GCC higher-level entities. .. Final Offline Assessment Tool (F-OAT) is in charge of: .. Producing precise OD&TS data (providing the OD&TS reference within the complete Galileo system) and performing the calibration of certain satellite models (e.g. Solar Radiation Pressure parameters) along with the precise OD&TS process (Satellite Model Calibration) .. Assessing OSPF performance by computing the Historical Signal-in-Space- Accuracy (HSISA) parameter, which is used to calculate the broadcast SISA value under nominal conditions. The SISA parameter is an a-priori statistical bound of the ranging errors affecting dualfrequency receivers that use the ephemeris and clock correction parameters computed by the OSPF for a particular service (OS, SoL, PRS). Different HSISA values are provided per satellite and per service. .. Assessing IPF performance by computing the Pre-Processing Error Calibration (PREC) performance parameter, which informs about the quality of the input at the integrity check. Different PREC values per each GSS station are provided, directly affecting the Signal-In-Space Monitoring Accuracy (SISMA) parameters computed by the IPF. .. CALG is a function used to generate and validate configuration files for other GMS facilities (i.e: OSPF, IPF, PTF, MUCF, ULS and MGF), based on external input data such as GRSP (Geodetic Reference Service Provider) products or IERS data, and configuration parameters generated within the F-OAT. CALG validation scenarios consist of: .. Manual Validation: The CALG operator validates manually the configuration files using the MMI (low DAL). After that, all the configuration files are sent to the CALG server (high DAL) to continue with the automated validation. .. Automated Validation: The CALG Scheduler periodically runs a number of algorithmic processes to ensure the consistency of external provided data with regard to extrapolated expected values computed within the MSF. This type of validation applies, for instance, to the Galileo Sensor Station (GSS´s) coordinates, which are one of the most sensitive parameters in terms of performance for the whole Galileo GMS. .. Signal Spectrum Analysis Tool (SSAT) analyses the Satellite’s Signal in Space (SiS) to check the signal characteristics with respect to their RF SIS specifications. The SSAT is mobile equipment, consisting of a Portable Workstation allowing remote control of a Vector Signal Analyzer (VSA), which is connected on-site to a 25m high gain tracking antenna. The VSA comprises the SiS acquisition and some automatic instrumentation-provided frequency domain measurements; and the workstation, apart from controlling the VSA, could host an analysis software allowing measurements in the time domain. Galileo Reference Scenarios (GRS) for the verification and validation of the MSF performances are defined for an IOV configuration (4 Galileo satellites and a network of 18 GSS stations), IOV + GPS (augmented IOV constellation with GPS signals) and FOC configuration (27 Galileo satellites + 40 GSS stations). This paper provides an overview of the most relevant requirements, design drivers, architecture and performance features of the MSF element.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	500 - 508
Cite this article:	Sánchez-Gestido, M., A.Ramírez-Jiménez,, Bertrand, F., Mediavilla, A.I., Bellido-Tirado, O., P.Falconio,, "Preliminary Design of the Galileo Mission Support Facility (MSF)," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 500-508.
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