Project Details
Projekt
Determination of Physical Heights via Time Transfer
Subject Area
Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
Term
since 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 490990195
As central observation quantity, we exploit the gravitational effect on the time scales at different locations as predicted by Einstein’s theory (i.e. the gravitational redshift). Using optical time transfer via satellite between highly-precise optical clocks, we will measure the difference of elapsed time between Wettzell and Braunschweig for observation periods of a few days. From this observable, we will determine the physical height difference between both sites. Innovative research elements in this project are i) the use of time instead of frequency as basic quantity to determine the physical heights or gravity potential differences between distant sites and ii) the exploitation of optical free-space links to a satellite instead of optical fibres over a rather long timespan, i.e. integration over days to achieve the required high accuracy. This does not only pose 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, instrumental effects) as well as all relevant corrections and reductions to the data such as tidal effects or changes due to more local mass variations to finally determine height differences with an accuracy of 20 cm.
DFG Programme
Research Units
