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Marisa Nickola
Type of contribution: poster

Determining HartRAO antenna reference point and axis offset parameters using VieVS

Marisa Nickola, HartRAO Alet de Witt, HartRAO Hana Kr'asn'a, TU Wien Ludwig Combrinck, HartRAO Johannes B"ohm, TU Wien

The 15-m and 26-m radio telescopes at the Hartebeesthoek Radio Astronomy Observatory (HartRAO) regularly participate in astrometric and geodetic VLBI sessions. The HartRAO 15-m telescope officially joined geodetic VLBI operations in 2013. In 2008 the HartRAO 26-m telescope suffered a critical bearing failure and only returned to operations in 2010 after it was repaired. Post-repair position time series solutions indicated no noticeable shift in the position. In 2014 the antenna axis offset for both the 15-m and 26-m were estimated using the Vienna VLBI Software (VieVS). A large discrepancy was found to exist between previously determined values of the antenna axis offset of the 26-m telescope (from ground surveys as well as from VLBI analysis before the bearing failure) and the VieVS determined values. Possible reasons for this discrepancy are being investigated. Further sessions have been included in the analysis and the VieVS obtained values of the antenna axis offset will also be compared to the local tie survey that was done in 2014. We are also looking at possible seasonal variations in both the antenna axis offset of the telescopes and, for sessions in which both HartRAO telescopes participated, also the baseline length between the two telescopes. A possible displacement of the antennas that may have occurred due to an earthquake in the vicinity of HartRAO during 2014 is also being investigated. We report here on the most recent results from our analysis.