African VLBI Network Training Site


Invited Talk: Thursday 19 April - Dr Aletha de Witt

18 April 2018 09:00 - 10:00

Title: History of the African VLBI Network

Author: Dr Aletha de Witt 
              Operations Astronomer
              South Africa


The African VLBI Network (AVN) will be a pan-African network of radio telescopes comprised of converted redundant satellite Earth-station antennas and new purpose-build radio telescopes. The first of these antennas, in Ghana, has been converted to a radio telescope and will be the second element, HartRAO the first, of what will become the AVN. The AVN, when initially conceived, was to be a modest network of newbuild 12-m class radio telescopes in the African Square Kilometre Array (SKA) partner countries. However, it was discovered that, as a result of new optical fibre connectivity into Africa, many large 30-m class telecommunications antennas were redundant and could be converted for astronomy purposes. There are 29 documented 30-m class telecommunications antennas in 19 African countries (though some have been destroyed). It is proposed that more of these can be converted and added to the AVN. Each addition will improve the present global VLBI networks. New radio telescopes may also be build.


More about the author:


Aletha de Witt obatined her Honours and Masters degree in Astrophysics and Space Science from the University of Cape Town (UCT) in South Africa. She obtained her PhD in Astrophysics from the University of South Africa (UNISA) in 2012.  In 2012 she joined the Hartebeesthoek Radio Astronomy observatory (HartRAO), first as post-doctoral research fellow and since 2013, as operations astronomer.  

Her research interest is focused on fundamental astronomy, in particular celestial reference frames and calibrator sources for Very Long Baseline Interferometry (VLBI). She is part of the International Astronomical Union (IAU) working group on the realisation of the next generation International Celestial Reference Frame (ICRF-3) to be adopted at the next General Assembly of the IAU in 2018.

Her main focus is the establishment of a celestial reference frame at K-band (22 GHz) and this project has received to date more than 600 hours of observing time on the Very Long Baseline Array (VLBA) and equal amounts of time on Southern VLBI instruments. She is also the principle investigator and scheduler for the majority of the Southern Hemisphere astrometric & geodetic VLBI sessions operated through the International VLBI Service for Geodesy and Astrometry (IVS).