As indicated in Table 5.1, at the epochs of 1992 November 22, 1993 July 3, and 1993 October 20, the SHEVE observations were made jointly with the VLBA. These simultaneous observations were designed to improve the u-v plane coverage for Centaurus A. The SHEVE array coverage of Centaurus A is generally north-south, missing east-west coverage. On the other hand, the VLBA telescopes which can observe to the declination of Centaurus A produce an east-west coverage. Thus, treating the SHEVE array and the VLBA as two sub-arrays and combining the data in the u-v plane, more detailed and reliable VLBI images can be obtained.
The VLBA data were obtained in Mark III mode and correlated at the VLBA correlator in Soccoro. The data obtained from 1993 July 3 are not yet available from the correlator. The VLBA and SHEVE data were fringe-fit and calibrated separately and merged together as two sub-arrays using the Caltech VLBI package task MERGE. The signal to noise match between the Mark II SHEVE data and the Mark III VLBA data was good since the SHEVE array was anchored by the 64 m antenna at Parkes and the 70 m antenna at Tidbinbilla. The visibility weights did not require adjustment.