CARA Science:
Automated Astrophysical Site-Testing Observatory (AASTO)

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Summary

The Automated Astrophysical Site-Testing Observatory (AASTO), is a self-powered, self-heated autonomous laboratory that hosts a suite of site-testing instruments. These instruments cover the spectrum from UV to submillimeter, and are intended to fully characterize potential astronomical sites at a variety of locations on the high Antarctic plateau. The CARA AASTO project enjoys strong collaboration with the University of New South Wales and the Mount Stromlo Observatory in Australia.

It is currently operational at South Pole station, and will later be deployed to remote, uninhabited sites on the high Antarctic plateau. It has a suite of astronomical site-testing instruments, so that potential observatory sites can be fully characterized over a wide range of wavelengths.

In addition to the astronomical site-testing data, the AASTO also collects weather data such as temperature, wind speed and direction, and atmospheric pressure.

The AASTO package consists of a suite of instruments:

Near-Infrared Sky Monitor (NISM)
This is the simplest instrument, with an InSb detector and fixed 2.35 micron filter cooled to 77K by a low-power Stirling cooler. NISM is designed to make only "Sky-dip" measurements. Placed to one side of the instrument is a black-body calibration source.

Mid-Infrared Sky Monitor (MISM)
The MISM is similar in concept to its near-IR counterpart, but uses a Stirling-cycle cooled HgCdTe detector. A chopping frequency of 1kHz is used to avoid 1/f noise. An ambient-temperature filter wheel yields spectral coverage from 4 to 14 microns.

Antarctic Fiber-Optic Spectrometer (AFOS)
The AFOS consists of a small telescope feeding a grating spectrometer and CCD detector via a bundle of six optical fibers. By observing bright stars, a direct measure of atmospheric transmission from the UV cut-on to about 800 nm is obtained. In addition, sky emission arising from aurorae and airglow can be monitored.

A full description of the AFOS, together with preliminary results, has been prepared by Boccas et al. (1998).

Sonic Radar (SODAR)
Acoustic radar which measures the height of the turbulent atmospheric boundary layer. Deployed in January 1999, it acquired several weeks of wind and microthermal data with 20 meter resolution to a height of up to 800 meters.

Generic Telescope Mount and DIMM (G-MOUNT and ADIMM)
Instruments under development by Australian National University for deployment in January 2000 to measure the seeing.

Submillimeter Tipper (SUMMIT)
Constructed by Carnegie Mellon University and the National Radio Astronomy Observatory and loaned to the AASTO project, the submillimeter tipper uses an ambient-temperature pyroelectric detector to monitor 350 micron radiation. A stepper motor drives an off-axis paraboloid mirror, allowing the instrument to scan from zenith to horizon. The tipper is currently taking data on the roof of the AST/RO building at the South Pole. Modifications to the tipper are planned to incorporate it within the AASTO package of instruments. For more information, see the submillimeter tipper website.

Results

The accomplishments of the project include:

Pictures

For more information

The group has a website at http://bat.phys.unsw.edu.au/~aasto/.

AASTO is based at the University of New South Wales, Australia, as part of JACARA, the Joint Australian Center for Astrophysical Research in Antarctica. For more information, contact Michael Ashley, mcba@newt.phys.unsw.edu.au.