Combined GPS and GALILEO Real-time Clock Estimation with DLR's RETICLE System

A. Hauschild, P. Steigenberger

Abstract:	With the launch of the first two In-Orbit-Validation (IOV) satellites on October 21, 2011, the build-up of the operational Galileo constellation has begun. Since December 14, 2011, and January 18, 2012, respectively, the two spacecraft are transmitting signals on the E1 and E5 frequency band. The signals have been tracked with the CONGO network, a global multi-GNSS receiver tracking network. The network consists of different types of GNSS receivers connected to broadband geodetic antennas. All receivers support tracking of triple-frequency observations for GPS and dual-frequency observations for Galileo. DLR’s Real-TIme CLock Estimation (RETICLE) system has been extended to provide real-time clock estimates for the new IOV satellites together with GPS and GLONASS based on the observations from the CONGO network and stations from the IGS real-time pilot project. The system is based on a Kalman-filter and estimates satellite clock parameters based on predicted orbits. The paper provides an overview of the data flow and processing scheme of the RETICLE system. The real-time orbit and clock products are compared to post-processed products in order to assess the quality of the orbit prediction and clock estimation. With currently only two spacecraft in orbit, the Galileo satellites cannot yet be used as an independent constellation in a practical way. Therefore, they are processed together with GPS, which requires the consideration of inter-system biases (ISBs) between Galileo and GPS signals. The nature and handling of inter-system biases in multi-constellation processing is discussed in further detail. Finally, the positioning performance of the realtime products for GPS-only and GPS+Galileo scenarios is demonstrated with Precise Point Positioning experiments with real tracking data.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	302 - 309
Cite this article:	Hauschild, A., Steigenberger, P., "Combined GPS and GALILEO Real-time Clock Estimation with DLR's RETICLE System," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 302-309.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In