Opening address and brief overview and aims of the Conference.

In recent years, a large amount of data has been collected with the aim to quantify the day- and nighttime astronomical observing conditions at Dome C. The available data show that the precipitable water vapor is below 0.75 mm in general, thus offering very good conditions for sub-mm observations. The extremely low temperatures of the atmosphere cause a very low background in the thermal infrared, which leads to significant savings in the time required to carry out large observing programmes. The absence of strong turbulence in the upper atmosphere results in a low scintillation and poses favorable conditions for photometric programmes. The free atmosphere seeing is of the order of $0\farcs 36$, but optical observations are impaired by the occurrence of a very strong turbulent boundary layer which reaches up to median altitudes of some 23 m in winter and up to some 400 m in summer. Detailed measurements of the vertical and temporal variation of the various parameters are now needed, in order to draw robust conclusions about short- and long-term stabilities and trends, and to constrain the specifications of future instruments that are eventually being deployed at Dome C.

The HAR observing methods such as Adaptive Optics and Interferometery, require a better understanding of the behavior of the perturbed wavefronts, more exactly a better knowledge of the atmospheric turbulence model in addition to the associate parameters. This is very crucial for modeling the HAR techniques and particularly for the evaluation of their performance. Indeed, it is well-known that the performance of an AO system depends upon the seeing conditions, the outer scale, the isoplanatic angle and the coherence time. A review of the site-testing instruments deployed at Dome C will be given, their pertinence and their implications on HAR techniques will be discussed comparatively to the Paranal site.

Site testing data provides an essential part of the justification for funding any new astronomical facility by defining the technological design and determining the telescope performance, thus allowing the scientific objectives to be prioritised. Here we review the current status of site testing at Dome C by examining the range of instruments that have been, or are planned to be, deployed to the site. We then investigate in more detail preliminary data which has so far proven crucial for telescope design, data for which discrepancies exist between two or more instruments, and required data for which there are no current plans to obtain. We discuss the implications of this data on the technical design, expected performance, and the scientific capabilities for a 2.5 m class optical/infrared telescope. Finally, we identify the site parameters that require further study, and define the experiments necessary to determine these parameters.

Atmospheric field experiments were made at the French-Italian station of Concordia at Dome C during several years. These experiments were limited to the summer season. In 2005 Concordia has become a permanent base, this allowed to carry out STABLEDC (STudy of the Atmospheric Boundary Layer Environmental at Dome C plateau station) that is an atmospheric field experiment of the duration of one year. The aim of STABLEDC was to study the processes occurring in the long-lived stable and the weak convective atmospheric boundary layers, observed during winter and summer, respectively, and to collect the relevant parameters for the atmospheric models. Both in situ and ground based remote sensing instruments have been used to monitor the meteorological parameters. The first part of the paper gives a brief illustration of the objectives of the field experiment, and a description of site and instrumentation. The second part shows the behaviour of some micrometeorological parameters: temperature, wind speed, sensible heat flux. The surface radiation balance components are also shown. Finally some experimental activities are proposed.

The internal antarctic plateau revealed in the last years to be a site with interesting potentialities for the astronomical applications due to the extreme dryness and low temperatures, the typical high altitude of the plateau, the weak level of turbulence in the free atmosphere down to a just few tens of meters from the ground and the thin optical turbulence layer developed at the ground. The main goal of a site testing assessment above the internal antarctic plateau is to characterize the site (optical turbulence and classical meteorological parameters) and to quantify which is the gain we might obtain with respect to equivalent astronomical observations done above mid-latitude sites to support plans for future astronomical facilities. Our group has been involved, since a few years, in studies related to the assessment of this site for astronomical applications that include the characterization of the meteorological parameters and optical turbulence provided by general circulation models as well as mesoscale atmospherical models and the quantification of the performances of Adaptive Optics (AO) systems. In this talk I will draw the status of art of this site assessment putting our studies in the context of the wide international site testing activity that has been done in Antarctica. I will focus on the site assessment relevant to astronomical applications to be done in the visible up to the near infrared ranges, i.e. those ranges for which the optical turbulence represents a perturbing element for the quality of the images and the AO techniques an efficient tool to correct these wavefront perturbations.

In January 2005, members of a Chinese expedition team were the first humans to visit Dome A on the Antarctic plateau, a site predicted to be one of the very best astronomical sites on earth.
In 2006, the Chinese Center for Antarctic Astronomy (CCAA) was founded to promote the development of astronomy in Antarctica, especially at Dome A. CCAA has since taken part in two traverses to Dome A, organized by the Polar Research Institute of China (PRIC), in the austral summers of 2007/2008 and 2008/2009. These traverses resulted in the installation of many site-testing and science instruments, supported by the PLATO observatory. The Chinese Small Telescope ARray (CSTAR) has produced excellent results from Dome A.
Our future plans include further site-testing work, and the following full-scale science instruments: three 0.5-m Antarctic Schmidt Telescopes (AST3), and a proposed 4-m telescope for wide-field infrared high spatial-resolution surveys. The first AST3 telescope is under construction and is scheduled for installation in 2011.

This paper presents some statistical information about the Concordia turbulent surface inversion layer, regarding height and turbulent energy, its contribution to the peculiar local seeing, and the free atmosphere seeing encountered just above this surface layer.

PLATO is a fully-robotic observatory designed for operation in Antarctica. It generates its own electricity (about 1 kW), heat (sufficient to keep two 10-foot shipping containers comfortably above 0°C when the outside temperature is at -70°C), and connects to the internet using the Iridium satellite system (providing ~30 MB/day of data transfer). Following a successful first year of operation at Dome A during 2008, PLATO was upgraded with new instruments for 2009.

The atmospheric properties above three sites (Dome A, Dome C and the South Pole) are investigated for astronomical applications using the monthly median of the analyses from the ECMWF (European Centre for Medium-Range Weather Forecasts). Radiosoundings extended on a yearly time-scale at the South Pole and Dome C are used to quantify the reliability of the ECMWF analyses in the free atmosphere as well as in the boundary and surface layers, and to characterize the median wind speed in the first 100 m above the two sites. Thermodynamic instabilities in the free atmosphere above the three sites are quantified with monthly median values of the Richardson number. We will present a ranking of the sites with respect to the thermodynamic stability, using the Richardson number, and with respect to the wind speed, in the free atmosphere (using ECMWF analyses) as well as in the surface layer (using radiosoundings).

We compare the merits of potential observatory sites on the Antarctic Plateau, in regard to the boundary layer, cloud cover, free atmosphere seeing, aurorae, airglow, and precipitable water vapour. We find that (a) all Antarctic sites are likely compromised for optical work by airglow and aurorae; (b) Dome A is the best existing site in almost all respects; (c) there is an even better site (“Ridge A”) 150 kms SW of Dome A; (d) Dome F is a remarkably good site except for aurorae; (e) Dome C probably has the least cloud cover of any of the sites, and might be able to use a predicted `OH hole' in the Spring.

It has already been demonstrated that a mesoscale meteorological model such as Meso-NH (Lafore et al. 1998) is highly reliable in reproducing 3D maps of optical turbulence (Masciadri et al. 1999; Masciadri & Jabouille  2001; Masciadri et al. 2004). Preliminary measurements above the Antarctic Plateau have so far indicated a pretty good value for the seeing: 0.27'' (Lawrence et al. 2004 ), 0.36'' (Agabi et al. 2006) or 0.4'' (Trinquet et al. 2008) at Dome C. However some uncertainties remain. That's why our group is focusing on a detailed study of the atmospheric flow and turbulence in the internal Antarctic Plateau. Our intention is to use the Meso-NH model to do predictions of the atmospheric flow and the corresponding optical turbulence in the internal plateau. The use of this model has another huge advantage: we have access to informations inside an entire 3D volume which is not the case with observations only. Two different configurations have been used: a low horizontal resolution (with a mesh-size of 100 km) and a high horizontal resolution with the grid-nesting interactive technique (with a mesh-size of 1 km in the innermost domain centered above the area of interest). We present here the turbulence distribution reconstructed by Meso-NH for 16 nights monitored in winter time 2005, looking at the the seeing and the surface layer thickness.

During winter and springtime, the flow above Antarctica at high altitude (upper troposphere and stratosphere) is dominated by the presence of a vortex centered above the continent. It lasts typically from August to November. This vortex is characterized by a strong cyclonic jet centered above the polar high. In a recent study of our group (Hagelin et al.  2008) of four different sites in the Antarctic internal plateau (South Pole, Dome C, Dome A and Dome F), it was made the hypothesis that the wind speed strength in the upper atmosphere should be related to the distance of the site to the center of the Antarctic polar vortex. This high altitude wind is very important from an astronomical point of view since it might trigger the onset of the optical turbulence and strongly affect other optical turbulence parameters. What we are interested in here is to localize the position of the minimum value of the wind speed at high altitude in order to confirm the hypothesis of Hagelin et al.  (2008).

Ground-based cosmological observations need a detailed knowledge about atmospheric transmission. A continuous monitoring of the transmission in the FIR/mm wavelength range is needed mainly due to H2O high frequency variations along the line of sight of a telescope. CASPER 2 (Concordia Atmospheric Spectroscopy of Emitted Radiation) is a spectrometer devoted to measurements of atmospheric emission in the millimetric region (4–12 cm-1, 120–360 GHz) with a spectral resolution of 0.2 cm-1. The instrument allows a continuous monitoring of the atmospheric transmission of the same sky region explored with MITO (Millimeter and Infrared Testagrigia Observatory, 3480 m asl, Italy) telescope, during cosmological observations.

The Antarctic Plateau is considered an ideal location for ground-based astronomy from the visible to the millimetric wavelength, thanks to both the low thermal emission and the high transparency of the atmosphere. The Microwave Limb Sounder instrument on board the AURA satellite, provides the vertical profiles of temperature, humidity and several gases present in atmosphere. These profiles can be used as input in radiative transfer model to simulate the atmospheric transmissivity at the different wavelengths.

The optical turbulence above Dome C in winter is mainly concentrated in the first tens of meters above the ground. The properties of this so-called surface layer were investigated during the last two winterover by a set of sonics anemometers placed on a 45 m high tower. These anemometers provide measurements of the temperature and the wind speed vector. The sampling rate of 10 Hz allows to derivate the refractive index structure constant Cn2. We report here the first analysis of these data.

A preliminary study of the precipitable water vapour (PWV) content above the observatories in Sierra Nevada, the southernmost high altitude location in continental Europe with a dry climate, indicates that Sierra Nevada is a very competitive location for FIR-submm observations, with a 25% quartile of PWV=2.3 mm(H2O) as compared with 2.1 mm(H2O) for Mauna Kea.

This report provides the recommendations of ARENA Working Group 1 concerning the development of and objectives for a wide-field, optical/infrared, 2.5 m class telescope for Antarctica. It discusses the key science drivers for such a telescope, the performance and capabilities it should have, and the logistics and infrastructure issues relevant to its construction and operation.

AGB stars are ideal IR targets because they are cool and bright. Most of them escaped detection in optical or shallow IR surveys in the eighties contributing to the puzzling missing number of AGB stars with respect to theoretical predictions and former stages of evolution. Observations and AGB models have advanced steadily in the following decades providing us with an almost complete view of the AGB stars in the Magellanic Clouds. Their properties are tracers of structure and chemistry across galaxies. New surveys will be able to fill-in the gaps, in terms of sensitivity and monitoring, providing new constraints for the formation and evolution of the Magellanic Clouds.

The gain of thermal infrared instruments in the 2–25 μm wavelength range from Antarctica is summarized by comparing three parameters: the ambient temperature; the atmospheric transparency, with perceptible water vapor content (PWV) in particular; and the image quality. For the 2 m class infrared telescope projects at Dome C the estimated mid infrared point source sensitivity can be compared to the sensitivities reached at 10 m class telescopes elsewhere. This comparison favors a thermal IR instrument at Dome C with focus on key science cases; two examples are: i) Survey type projects, such as mid infrared photometric imaging or spectro–polarization campaigns of YSO. Or ii) monitoring and rapid response observations on the Galactic Centre, the LMC, SN or GRB.