The Trans-Antarctic Mountain range behind BTN
 
 
     

The Automated Astrophysical Site-Testing Observatory (AASTO)
1997 - 2005

   

   

Fisheye view of the AASTO shelter, 650 metres from the Geographical South Pole, at South Pole Station.

The AASTO, the world's southernmost astronomical observatory
(latitude -89d 59m 39s)
, was decommissioned in December 2005. Information on the AASTO project is retained below for historical purposes.

The instruments

Completed instruments, installed between 1997 and 2000:

  • SODAR Sonic radar experiment (UNSW), to measure the turbulence in the atmosphere as a function of height using a Remtech PA-1 sodar.

    Here is some data from mid-2000. Each vertical line shows the result of averaging 30 minutes of data, covering 30 altitude bins from 20 to 890 metres above the ice.

  • AFOS The Antarctic Fibre-Optic Spectrometer (UNSW), this instrument is the one that looks most like a telescope. It is made entirely from invar (a low-expansion coefficient steel) and astrosittal (a low-expansion coefficient glass), with no provision for adjustment. We align it in the lab in Sydney at 20C, and it will stay aligned in Antarctica at -80C. The AFOS points at bright stars and sends the light down two bundles of optical fibres into a spectrometer in the AASTO. The signal from the spectrometer is measured using a CCD camera manufactured by Andor Technology. The purpose of the AFOS is to determine the transmission of the Earth's atmosphere from UV wavelengths to the visible red.
  • NISM The Near-Infrared Sky-Monitor (UNSW), measures the emission from the Earth's atmosphere in the near-infrared (at 2.35 microns to be precise). This wavelength was choosen since it is in the centre of a band where there is no emission from molecules in the Earth's atmosphere, and so the sky is darkest. In fact, our IRPS experiment (at South Pole from 1993 to 1996) has already shown that the sky is 40 to 100 times darker at the Pole at 2.35 microns than the best alternative ground-based observatories. The NISM will further quantify this result, and allow us to test the sky away from the Pole.
  • MISM The Mid-Infrared Sky-Monitor (UNSW), just like the NISM, except it works in the mid-infrared (out to 15 microns). No one has yet sampled the mid-infrared in Antarctica during the winter (i.e., nighttime). Craig Smith of the Australian Defence Force Academy made measurements during the summer of 1996, and showed factors of ten or more improvement over alternative sites.
  • Summit Submillimeter Skymonitor (NRAO/Carnegie-Mellon/UNSW), similar to the NISM and MISM except for longer wavelengths still. We are winterising this instrument now, and plan to ship it to the Pole at the end of 2000.
  • GTOWER The Generic Tower (Yerkes). A 7.5 metre tower built at the University of Chicago to support the AFOS and ADIMM above ice. This is an impressive structure that can be deployed from a Hercules and assembled by a couple of people in a day or so. It is able to support 500 kg or more with great stability.
  • GMOUNT The Generic Mount (Mt Stromlo), a low-power (20W) telescope mount, able to support two telescopes weighing 70 kg each, and with an absolute pointing accuracy of a few arcseconds. The mount is computer-controlled and able to self-calibrate.
  • ADIMM The Antarctic Differential Image Motion Monitor (Mt Stromlo), a telescope based on Celestron 14 optics (with everything else replaced). It will measure the astronomical ``seeing'' in the visible, i.e., how much do the stars twinkle. Our balloon-borne and tower experiments conducted during 1994-95 have shown that about 200 metres above the ice the star images are about a factor of 2 times smaller (i.e., better) than the very best alternative ground-based observatories. There are good reasons to believe that this good ``seeing'' will extend all the way to the ground at locations on the Antarctic plateau where the prevailing wind direction is just right. The ADIMM will be able to test this hypothesis. If it is true, it will revolutionise ground-based astronomy, if it is not true, then building a 200 metre tower is still a lot easier than launching a telescope into space!
Instruments for future grant applications:

A submillimeter phase-stability instrument based on measuring the phase relationship of satellite beacons.

The AGO project

The AASTO itself is derived from the successful US AGO, or Automated Geophysical Observatory. The sixth and final AGO was deployed in January 1997, at the same time that the AASTO came on-line. More details of the AGO program can be found at Augsburg College and the University of Maryland.

Health and status data

Housekeeping data are sent out from the AASTO every 90 minutes via polar orbiting ARGOS satellites. These data are collected by Augsburg College as part of the AGO program. You can see the latest report from the AASTO (updated daily) by clicking here (note that the AASTO is listed as ``AGO-A2''; further note: the AASTO is not transmitting during 2000 since the ARGOS control unit has been returned to Sydney for repair). The data displayed include ``health'' information such as burner temperatures and voltages, instrument current drains, and meteorological data. At the present time there is a calibration problem with the data acquisition system, so not all of the data displayed is accurate.

Will the AASTO be making any astronomical discoveries?

No. The instruments on-board the AASTO are purely designed for site-testing. Three of them (NISM, MISM, and Summit) are looking at emission from the Earth's atmosphere. One (the Sodar) is measuring atmospheric turbulence. Two (AFOS and ADIMM) are using bright stars as probes of the atmosphere's transmission and stability.

How much is the AASTO project costing?

The AASTO is about a AUD$1 million project on the Australian side, with roughly equal contributions from UNSW, ANU, and the Australian Research Council. We have also received AUD$25K from the Australian Antarctic Foundation which was used to purchase the CCD system for the AFOS.

Logistical support from the US National Science Foundation through our collaborators in the Center for Astrophysical Research in Antartica is conservatively estimated at another AUD$1 million.

What are our plans for the future?

We already know that the South Pole is a superb site for near- and mid-infrared astronomy. It would make a great deal of sense to build a small (2-metre aperture) telescope at the South Pole to exploit these windows. When the AASTO results are in, we will know the best site on the plateau to build a telescope, and the wavelength regions that are most promising. A medium-to-large size multinational observatory could then be established, on a timescale of perhaps 15 years.

The JACARA Tee-Shirt

The official Joint Australian Centre for Astronomical Research in Antarctica (JACARA) Tee-Shirt is now available in two designs, and in all sizes, for $20. Contact Michael Ashley for ordering information.

The movie

So, you've bought the tee-shirt, now see the movie! The Deep Black is a professionally-produced 52-minute documentary made by the Audio-Visual Unit here at UNSW. It is currently being shown on Optus Vision Horizon channel, and is available for purchase from UNSW. Contact Michael Ashley for details.

Minutes of the AASTO Working Group Only the early discussions are on-line.
  1. 23 May 1994; Boulder, Colorado, USA
  2. 1 April 1995; Mt Stromlo Observatory; Canberra, Australia
  3. 23 March 1996; Mt Stromlo Observatory; Canberra, Australia
  4. 24 May 1996; University of New South Wales; Sydney, Australia
  5. 26 July 1996; University of New South Wales; Sydney, Australia
Other Antarctic instrumentation web sites

Last updated 22-Sep-1999

Michael Ashley