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In ancient times, looking at the stars was essential for navigation. Today, we make use of artificial satellites for our position, navigation and timing applications, giving the impression that there is no need for astronomers any more telling us where to go or what time it is. Well, this is not the case. Modern satellite techniques rely on precise knowledge of their orbits in space, which needs to be determined in an absolute manner. In geodetic Very Long Baseline Interferometry (VLBI), we use extra-galactic black holes (quasars) as anchor points, allowing to disentangle satellite orbits from the irregular movements of the Earth. It is the only technique capable of measuring the full set of Earth orientation parameters, which are precession and nutation, polar motion and dUT1, the difference between the actual rotational speed of the Earth to an atomic time scale.
VLBI is a global instrument which is currently organised on a best effort basis only, relying on the voluntary contributions from national mapping authorities, research institutions, observatories, and Universities. This is a major gap in resilience in our modern world, a topic recently highlighted by the United Nations.
In this talk, I will present Australia’s contribution to international geodetic VLBI and its links to the radio astronomy community. While the core products mainly find their way into enabling sciences such as the world’s most precise coordinate frame, more recent applications of VLBI can be found in upcoming space missions (e.g. ESA’s NovaMoon) or intercontinental time and frequency transfer. Current risks and challenges will also be discussed, such as the rapidly increasing man-made radio emissions in space caused by providers of internet via satellites. Improved protection of VLBI frequencies on a global scale is an urgent need if we want satellite services being able to continue operations. This is where science meets policy and international treaties and I will report about current work on this matter at the national level.
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