The Galileo System Test Bed V2 for Orbit and Clock Modeling

R. Píriz, V. Fernández, A. Auz, P. Tavella, I. Sesia, G. Cerretto, M. Falcone, D. Navarro, J. Hahn, F. González, M. Tossaint, M. Gandara

Abstract:	In preparation for the development of the Galileo system, the European Space Agency launched in 2002 the development of an experimental ground segment (Galileo System Test Bed Version 1). Within the GSTB-V1 project, tests of Galileo orbit determination, integrity and time synchronization algorithms were conducted with the GPS satellites and an experimental ground segment consisting of a worldwide network of sensor stations collecting high quality GPS observables at 1 Hz, an Experimental Precision Timing Station providing the reference time scale steered to UTC/TAI, and a Processing Center located at the European Space Agency (ESA-ESTEC) in The Netherlands. The latter was used for the generation of navigation and integrity core products based on Galileo-like algorithms. Within the Galileo System Test Bed Version 2 project (GSTB-V2), two experimental satellites called GIOVE-A and GIOVE-B are being launched. They will mark the first step in the validation of the Galileo system to be completed with the deployment of the In-Orbit Validation satellites. The GIOVE-A satellite has been developed by Surrey Satellite Technology Ltd (UK). GIOVE-A was launched from the Baikonur cosmodrome by a Soyuz rocket on December 28th 2005. The GSTB-V2 Mission Experimentation project is intended to mitigate the Galileo project risks by an early assessment of technical aspects like early demonstration and performance assessment of the navigation service (including navigation message generation, uplink and broadcast), validation of critical in-orbit technology (clocks), end-toend analysis of the Galileo Signal-In-Space, assessment of Galileo Test Receiver performance, validation of existing ground algorithm prototypes (from GSTB-V1) and testing of new ones (e.g. ionosphere and Broadcast Group Delay), and overall testing of timeliness and operational aspects. The GSTB-V2 core infrastructure for experimentation consists mainly of a network of Galileo Experimental Sensor Stations (GESSs) worldwide distributed that acquire and collect the GSTB-V2 satellite signals and send pseudorange and carrier phase measurements to a Ground Processing Center (GPC) located at ESTEC (upgraded from GSTB-V1). One GESS is to be installed at the Time Laboratory located at INRiM, Turin, connected to an Active Hydrogen Maser, located in a controlled environment. The INRiM time reference will be used as the basis for Galileo System Time (GST) in GSTB-V2. SLR stations from the ILRS network send measurements to the GPC as well. This paper describes the scope and goals of the GSTB-V2 Mission Experimentation and presents the first GIOVE-A orbit and clock analysis results obtained during the early stages of the project.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	549 - 562
Cite this article:	Píriz, R., Fernández, V., Auz, A., Tavella, P., Sesia, I., Cerretto, G., Falcone, M., Navarro, D., Hahn, J., González, F., Tossaint, M., Gandara, M., "The Galileo System Test Bed V2 for Orbit and Clock Modeling," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 549-562.
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