Determination of physical heights via time transfer (P5)

P5 will determine the gravity potential respectively the physical height difference by a comparison of optical clocks at two remote sites used in combination with optical time transfer..

To realize this goal, we will operate a strontium optical lattice clock at the Physikalisch-Technische Bundesanstalt (PTB), Germany's National Metrology Institute. This clock is connected through a dedicated delay-compensated optical fiber to the SLR Station at GFZ Potsdam. The two geodetic observatories Potsdam and Wettzell will be linked by optical time transfer via ACES. The timing system in Wettzell will be controlled by the optical clock SOC2 developed at the University of Düsseldorf.

Thus, the central observation of this project is the use of time (instead of frequency) as basic quantity to determine the physical heights or gravity potential differences between distant sites and the exploitation of optical free-space links (instead of only fibers) over a rather long timespan, i.e. integration over many days to achieve the required high accuracy. This does not only pose some challenges on the involved clocks and links, but also on the data analysis. We will investigate the dominant error sources (like different clock/link behavior, atmospheric effects) as well as all relevant corrections and reductions to the data such as tidal effects or changes due to more local mass variations. This innovative approach will serve as a showcase for accurately transferring physical heights between remote geodetic sites via time transfer using an optical free-space link. Moreover, we will demonstrate the added value of the Research Unit’s time concept to integrating geometric and physical heights for future height systems in general and for GGOS core stations such as the Geodetic Observatory Wettzell especially.
 

Publications:

• Test1
• Test2