Dr. Christoph Günther, Director, German Aerospace Center (DLR), Germany

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User positioning in satellite navigation relies on pseudoranges, accurate orbits and the synchronization of satellite clocks. The latter requires extremely stable atomic clocks as well as the accurate characterization of their offsets with respect to a common basis called system time. The topics (ultra-) stable clocks and system time are addressed in separate tutorials. Together with accurate orbits, they are the basis for the current performance of GPS, GLONASS, Galileo and Beidou. Additionally, pseudoranges from the corresponding satellites are a central element for comparing time over continents in order to create Time Atomic International. The current approach to satellite navigation, which relies solely on the measurement of pseudoranges, needs a substantial amount of modelling. The newly proposed Kepler System follows a different approach and does not require long-term stable clocks for navigation anymore. It directly synchronizes the satellites using optical intersatellite links and uses these links to provide ultra-accurate ranges for orbit determination as well. An additional constellation of 6 or more LEO satellites furthermore enables the direct observability of L-band signal biases and phase center variations. As a consequence, the Kepler System has the potential of achieving centimeter-accurate positioning globally without further augmentation. Additionally, an ultra-stable clock (discussed in a separate tutorial) introduced in the “perfectly” synchronized Kepler system provides a global time reference which might be used in multiple ways. Christoph Günther studied theoretical physics at the Swiss Federal Institute of Technology in Zurich. He received his diploma in 1979 and completed his PhD in 1984. He worked on communication and information theory at Brown Boveri and Ascom Tech. From 1995, he led the development of mobile phones for GSM and later dual mode GSM/Satellite phones at Ascom. In 1999, he became head of the research department of Ericsson in Nuremberg. Since 2003, he is the director of the Institute of Communication and Navigation at the German Aerospace Center (DLR) and since December 2004, he additionally holds a Chair at the Technische Universität München (TUM). His research interests are in satellite navigation, communication, and signal processing.