The AUSTRAL VLBI observing program

Abstract

The AUSTRAL observing program was started in 2011, performing geodetic and astrometric very long baseline interferometry (VLBI) sessions using the new Australian AuScope VLBI antennas at Hobart, Katherine, and Yarragadee, with contribution from the Warkworth (New Zealand) 12 m and Hartebeesthoek (South Africa) 15 m antennas to make a southern hemisphere array of telescopes with similar design and capability. Designed in the style of the nextgeneration VLBI system, these small and fast antennas allow for a new way of observing, comprising higher data rates and more observations than the standard observing sessions coordinated by the International VLBI Service for Geodesy and Astrometry (IVS). In this contribution, the continuous development of the AUSTRAL sessions is described, leading to an improvement of the results in terms of baseline length repeatabilities by a factor of two since the start of this program. The focus is on the scheduling strategy and increased number of observations, aspects of automated operation, and data logistics, as well as results of the 151 AUSTRAL sessions performed so far. The high number of the AUSTRAL

Fast jet proper motion discovered in a blazar at z=4.72

“…The high-redshift blazar J1430+4204 was observed in the session aov22 (Table B1), with a global network consisting of ten radio telescopes providing baseline lengths up to ≈ 10 000 km. The participating antennas were Badary (32 m diameter), Svetloe (32 m), Zelenchukskaya (32 m) from the Russian "QUASAR" VLBI network [57]; Kunming (40 m), Sheshan (25 m) from China VLBI network [58]; Hobart (26 m), Katherine (12 m), Yarragadee (12 m) from Australian VLBI network [59]; Warkworth (12 m) from New Zeland, and Ishioka (13 m) from Japan. For our target J1430+4204, six scans of 6-8 min were scheduled in this session, spreading over 12 h, and providing a good (u,v) coverage for image reconstruction.…”

Star Scheduling Mode—A New Observing Strategy for Monitoring Weak Southern Radio Sources with the AuScope VLBI Array

“…In the regular AUSTRALs, we find a maximum of 35 scans per hour for the 12-m telescopes. It has been shown (Plank et al 2017) that this improves the geodetic results in terms of baseline length repeatabilities compared to typically 10–15 scans per hour in the standard IVS experiments. We conclude that including observations of weak sources in the schedule does not significantly diminish the geodetic quality of the schedule measured by the number of scans for each station.…”

“…The new Australian antennas in Katherine (Ke, Northern Territory), Yarragadee (Yg, Western Australia), and Hobart (Hb, Tasmania) have been regularly participating in the international observing programmes coordinated by the International VLBI Service for Geodesy and Astrometry (IVS, Nothnagel et al 2016). In parallel, the AUSTRAL observing programme (Plank et al 2017) was established, having the aim to optimally utilise the new VLBI infrastructure and further improve the results for the Australian region. The Warkworth 12-m antenna (Ww) also participates in the AUSTRAL programme.…”

“…In order to achieve better geodetic results through more observations, only strong sources are observed in the AUS-TRAL sessions (Plank et al 2017). An exception are those sessions with an astrometric purpose or those with the addition of larger and thus more sensitive antennas to the array.…”

Observing APOD with the AuScope VLBI Array

“…Changing the observation mode when switching between quasars and APOD was not an option as it might have introduced unknown systematic biases. The observation mode has been slightly modified from the mode used for the AUSTRAL sessions described in [ 35 ]. Data was recorded in 16 channels with 16 MHz bandwidth each, 10 in the X-band and 6 in the S-band, applying 2-bit sampling, which results in a recording rate of 64 Mbps per channel.…”