African VLBI Network Training Site


Invited Talk: Friday 31 May - Dr Aletha de Witt


31 May 2019 11:30 - 12:30

Title: The African VLBI Network

Author: Dr Aletha de Witt 
              Operations Astronomer

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-built radio telescopes. The first of these antennas, in Ghana, has been converted to a radio telescope and will be the second element, HartRAO being the first, of what will become the AVN. The AVN, when initially conceived, was to be a modest network of new-built 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 Master's 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). Alet was part of the International Astronomical Union (IAU) working group on the realisation of the next-generation International Celestial Reference Frame (ICRF-3) that was adopted at the General Assembly of the IAU in 2018.

Her main focus is on the establishment of a celestial reference frame at K-band (22 GHz) and this project has, to date, received 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).