What is VLBI?

Very Long Baseline Interferometry (VLBI) is a cutting-edge space geodetic technique that plays a central role in modern geodesy. It is a microwave-based technique that measures the difference in arrival times of signals from a radio source to telescopes by cross correlation. 

Most commonly the observed radio sources are extragalactic objects, such as active galactic nuclei, but beacons from satellites have been used as well. By observing extragalactic objects VLBI is able to connect the surface of the Earth to the stable celestial background. These observations make it possible to derive an absolute orientation of the Earth, which is one of the advantages of VLBI over other space geodetic techniques.

VLBI team at TU Wien

Our VLBI team strongly contributes to TU Wien’s strategic goals outlined in fuTUre fit strategy paper. 

Constant international visibility and recognition for our team members in the world-wide scientific VLBI community is achieved through their deep involvement in conducting research on providing a global geodetic reference frame for sustainable development, based on Resolution 69/266, opens an external URL in a new window adopted by the United Nations General Assembly in 2015. 

Members of the VLBI team at TU Wien belong to the world’s scientific leaders in developing strategies to improve the precision and accuracy of essential geodetic variables (EGV), which provide the framework for all geospatial activity, as a key enabler of spatial data interoperability, disaster mitigation, sustainable development and societal progress.

The unique profile of our VLBI group, which covers all tasks of the VLBI data process chain, enables us to fully explore the potential of the VLBI technique with a special focus on creativity, innovation and scientific freedom in our work.

Our students have the opportunity to be involved in basic science research and contribute to the advancements of VLBI as part of an internationally well-established group within the International VLBI Service for Geodesy and Astrometry (IVS website, opens an external URL in a new window), and within the International Earth Rotation and Reference Systems Service (IERS website, opens an external URL in a new window).

Essential geodetic variables (EGV)

From our VLBI analysis we provide the following EGV as defined by the Global Geodetic Observing System of the International Association of Geodesy: 

• Earth Orientation Parameters
• Celestial Reference Frame
• Terrestrial Reference Frame
• Station positions and variations

The Vienna Center for VLBI (https://www.vlbi.at, opens an external URL in a new window) is operated jointly by TU Wien and the Austrian Federal Office of Metrology and Surveying (BEV).