OPTIMIZING THE AFRICAN VERY LONG BASELINE INTERFEROMETRY NETWORK (AVN) FOR ASTRONOMY, GEODESY AND ASTROMETRY: A CASE STUDY FOR KENYA.

The African VLBI Network (AVN) will be an African array 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 into a radio telescope. There are plans and limited funding, to convert antennas in Kenya, Madagascar and Zambia. The Kenyan antenna is based at the Longonot Earth Station, in Nakuru County. It is a 32 m dish that will be converted for radio astronomy purposes. In this study, the value that these African radio telescopes, and in particular the Kenyan telescope, will add to the AVN, as well as the global VLBI networks for astronomy, geodesy and astrometry, is reviewed.

The impact of the AVN on astronomical, geodetic and astrometric products was investigated through simulated VLBI observations. The radio frequency interference (RFI), atmospheric weather conditions and the u-v coverage of these sites were also assessed.

The Kenyan site has little human generated RFI and is naturally shielded by a mountain. The site is also relatively dry and thus suitable for high-frequency VLBI observations. The Namibian site has the least RFI and little precipitation and thus suitable for VLBI observations at any frequency. The Kenyan antenna contributes significantly to the u-v coverage when added to the EVN network and comes in third after Mauritius and Madagascar when added to the LBA network. The AVN antennas reduce the errors in EOPs by half through simulated geodetic VLBI experiments and the Kenyan antenna singularly almost halves the error in the declination of the source in source position estimates through simulated astrometric VLBI experiments since it provides the longest baseline lengths to the VLBI network in the Southern Hemisphere, the LBA.

 Conversion of these dishes into radio telescope is an expensive affair and no significant evaluation of the optimization of the AVN has been completed. This study will inform which of the AVN antennas to convert first, where to build new ones and what next-generation instruments and receivers they should have.

Director INST

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