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Australia Telescope Compact Array Home Page

"The MM-Wave Upgrade"

The Australia Telescope Compact Array (ATCA) is a radio interferometer consisting of six 22-m antennae aligned along a 6-km-long, east-west track. It is currently operating in four frequency bands around 1.4 GHz (20 cm), 2.3 GHz (13 cm), 4.8 GHz (6 cm), and 8.6 GHz (3 cm), achieving a maximum angular resolution of one second of arc (1"), which is similar to the resolution reached by ground-based optical telescopes.

The Australia Telescope Compact Array

Fig. 1: Five antennas of the ATCA. (copyright CSIRO, photo J. Masterson)


The ATCA Upgrade, which is part of the Major National Research Facility (MNRF) program, will allow astronomers to observe at even higher frequencies, around 22 GHz (12 mm) and 90 GHz (3.5 mm). The ATCA will thus be the first millimetre interferometer in the Southern Hemisphere! And, at the above frequencies, it will be at least as good as existing millimetre interferometers in the Northern Hemisphere.

The ATCA Upgrade will open a number of new opportunities; these are set out below.
The nuclei of two colliding galaxies, NGC 4038/9 also called
 ``The Antennae'', observed at a wavelength of 13 cm.

Fig. 2: The nuclei of two colliding galaxies, NGC 4038/9 also called ``The Antennae'', observed at a wavelength of 13 cm.


The ATCA Upgrade involves the following projects:

Fig. 3: Six telescopes make 15 two-element interferometers. Shown are the tracks of each interferometer observing a source at a declination of -50 degrees. Displayed on the left is the uv-coverage of a 12-h observation with the telescopes aligned on the current east-west track (Figure 1). The more dense and uniform the coverage the easier it is to reconstruct an image of the source from the observations. Seen on the right side is a combination of two 6-h observations, one with a standard east-west array and the other with a new configuration including the north-south spur. This observing mode will be used mainly at high frequencies to avoid taking data at low elevation where the atmospheric attenuation is large. --- Using a Java applet you can create your own Virtual Radio Interferometer (V.R.I.) at http://wwwnar.atnf.csiro.au/astronomy/vri.html.

All projects are well under way and completion is expected in January 2002. Until then we will use the 22-m Mopra antenna near Coonabarabran and, for example, the 15-m Swedish-ESO Submillimetre Telescope (SEST) in Chile at high frequencies, but relatively low resolution (about 40"), to prepare for the future millimetre observations of the upgraded ATCA.

The 22-m Mopra antenna

Fig. 4: The 22-m Mopra antenna. (copyright CSIRO, photo J. Masterson)



More up-to-date information on the individual projects, especially the 3.5-mm system upgrade, and related topics, can be found on the World-Wide-We at http://www.atnf.csiro.au/overview/mnrf/projects/3.5mm/3.5mm_project.html.