An experienced observer is available at all times during observations: the Duty Astronomer (DA). The Duty Astronomer roster is given at http://www.narrabri.atnf.csiro.au/observing/support/, or if you are observing at the ATCA, find out who your Duty Astronomer is by looking on the whiteboard on the wall opposite the terminals in the Control Room. If you have a problem you cannot solve yourself you should first approach your DA.