(A copy of an article to appear in the IVS Newsletter, Dec 2013)

Jim Lovell, Stas Shabala, Jamie McCallum & John Dickey : University of Tasmania Cormac Reynolds : Curtin University Sergei Gulyaev, Tim Natusch & Stuart Weston : Auckland University of Technology Jonathan Quick : Hartebeesthoek Radio Astronomy Observatory Johannes Böhm & Lucia Plank : Vienna University of Technology Jing Sun : Shanghai Astronomical Observatory

The AuScope VLBI Project recently received additional operational funds which will allow the VLBI array to participate in 170 days of observations per year until July 2015. Sixty of these days will be dedicated to AUSTRAL sessions with scheduling in the Vienna VLBI Software VieVS, observations with the three AuScope antennas plus Warkworth 12m and Hartebeesthoek (15m and 26m), and correlation at Curtin University.

The AUSTRAL observing program is divided into three streams focused on high priority geodetic and astrometric aims:

• 12 days per year will be dedicated to astrometric observations to monitor and enhance the southern hemisphere reference frame in preparation for ICRF3.
• 18 days per year to improve the density of the time series for the southern antennas and to measure and monitor the motion and deformation of the Australian plate. This will also act as a demonstration of the capabilities of the AuScope array by tailoring observations for high data rates and smaller antennas.
• Four 15 day CONT-like sessions over the next two years. The first session will commence on Nov 28, 2013 with another a year later and two more in 2015. As has been demonstrated in previous CONT sessions, the fixed array, multi-day observations demonstrate the current capabilities of geodetic VLBI and reveal the level of systematic errors in the solutions (e.g. Lovell at al 2013, JoG 87, 527). The AUSTRAL-CONT sessions will be used to examine these effects in more detail, in particular the influence of source structure (Charlot 1990 AJ 99, 1309; Shabala et al 2013, JoG submitted). The 2013 session will be scheduled such that the individual source observations are repeated at the same sidereal time so the interferometer response to structure is kept constant from day to day. We will observe 3 source samples over 5 days each, selected on their Structure Index (SI). One sample will contain low SI sources only, another with high SI only and a third with a source selection typical of usual Rapid observations. In this way we hope to characterise the level of source structure influence in geodetic solutions and isolate its effects from other influences such as the troposphere.