Introduction

The high Antarctic Plateau is considered the best site on Earth for astrophysical observations in the millimetric and sub-millimetric wavelength ranges (Burton et al. 1994). In the last few years many astrophysical experiments have been deployed on this continent (Ruhl et al. 1995; Viper Home Page; Balm 1996; Storey, Ashley & Burton 1996 1996; Valenziano et al. 1998) and large telescope projects are presently being developed (Stark 1998). The main astrophysical observing site, already operational, is the U.S. Amundsen-Scott station at the South Pole (SP hereafter), where the CARA (Center for Astrophysical Research in Antarctica) installed quite a large laboratory. Data on the observing conditions at SP have already been reported in the literature (Dragovan et al. 1990; Chamberlin & Bally 1994; Chamberlin 1995; Chamberlin, Lane & Stark 1997; Lane 1998), while sophisticated tests are being performed by Australian researchers, using an automated instrument (Storey, Ashley & Burton 1996).

Italy has been deeply involved in astrophysical activities in Antarctica since 1987. The Italian Antarctic Program (PNRA - Programma Nazionale di Ricerche in Antartide) established an astrophysical observatory (OASI, Osservatorio Antartico Submillimetrico e Infrarosso, Dall'Oglio et al., 1992) at the Italian station Baia Terra Nova (74 41' 36" S, 164 05' 58" E). A 2.6 meter sub-millimetric telescope is operating there during the southern summer season. Many facilities are available, including Nitrogen and Helium liquefiers, mechanical workshops, electronic and cryogenic laboratories. The site quality is comparable to mid-latitude mountain observatories for millimetric (Dall'Oglio et al. 1988) and mid-infrared observations (Valenziano 1996).

In 1994, Italy and France started a program for building a permanent scientific station (Concordia) on the high antarctic plateau, at Dome C, hereafter DC, (75 06' 25" S, 123 20' 44" E). Domes are regions more elevated than the rest of the continent (DC is at 3280 m), barring the Trans Antarctic Mountains. The highest is Dome A (4100 m), potentially the best observing site on the planet, but it is very difficult to reach.

In December 1995, a test experiment was run to directly compare the short term atmospheric stability (the so-called sky noise) between DC and the Italian station on the coast. Raw data show a reduction in rms noise of factors of 3 and 10 at =2 mm and =1.2 mm respectively (Dall'Oglio 1997). In December 1996 the APACHE96 (Antarctic Plateau Anisotropy CHasing Experiment) (Valenziano et al., 1997,1998) was set up at DC. Preliminary data analysis shows good atmospheric stability in terms of sky-noise at mm wavelengths. Atmospheric PWV content was measured during the latter mission.

The AASTO experiment, presently running at the SP, is planned to be moved to DC in the next few years. It will allow a careful assessment of the observational quality at DC over a wide wavelength range. However, some interesting information can be obtained from meteorological data, taking advantage of the good statistics based on data collected over eight years.

The AWS project, started in the early 80s, installs automatic units in remote areas of the Antarctic continent. The main objective of this program is to support meteorological research by unattended, low cost, data collecting stations. AWS units operate continuously throughout the year. AWS data for all the stations are publicly available at the University of Wisconsin - Madison. One AWS unit is located a few kilometers from the Concordia Station site. Therefore, it shares the same atmospheric conditions as the planned astrophysics observatory. Another unit is at the geographical SP (Clean Air, elevation 2836 m). Therefore it is possible to compare the two sites on the basis of homogeneous data.

The main goal of this paper is to present data on DC conditions and to compare them with those of well established observing sites. They are useful for planning experiments and for stimulating a deeper exploration of this interesting and promising observing site.

© Copyright Astronomical Society of Australia 1997