Preliminary site testing results at Dome C (Antarctica) are presented, using both Automatic Weather Station (AWS) meteorological data (1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993) and Precipitable Water Vapour (PWV) measurements made by the authors. A comparison with the South Pole and other sites is made. The South Pole is a well established astrophysical observing site, where extremely good conditions are reported for a large fraction of time during the year. Dome C, where Italy and France are building a new scientific station, is a potential observing site in the millimetre and submillimetre range. AWS are operating at both sites and they have been continuously monitoring temperature, pressure and wind speed and direction for more than ten years. Site testing instruments are already operating at the South Pole (AASTO, Automated Astrophysical Site-Testing Observatory), while light experiments have been running at Dome C (APACHE, Antarctic Plateau Anisotropy CHasing Experiment) during summertime. A direct comparison between the two sites is planned in the near future, using the AASTO. The present analysis shows that the average wind speed is lower at Dome C (∼1 m s −1 ) than at the South Pole (∼2 m s −1 ), while temperature and PWV are comparable.

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We report simultaneous observations of the X-ray cluster RX J0658[5557 at 1.2 and 2 mm made with a double-channel photometer on the Swedish ESO Submillimeter Telescope (SEST) in search of Sunyaev-Zeldovich (SZ) e †ect. The SZ data were analyzed using the relativistically correct expression for the Comptonization, and we Ðnd (2.60^0.79) ] 10~4 from the detected decrement, which is consistent with that computed using the X-ray (ROSAT and ASCA) observations. The uncertainty includes contributions from statistical uncertainties in the detection, systematics, and calibration. The 1.2 mm channel data alone give rise to a larger Comptonization parameter ; this result is discussed in terms of contamination from foreground sources and/or dust in the cluster or from a possible systematic e †ect. We then make use of a combined analysis of the ROSAT and ASCA X-ray satellite observations to determine an isothermal model for the SZ surface brightness. Since the cluster is asymmetrical and probably in a merging process, models are only approximate. The associated uncertainty can, however, be estimated by exploring a set of alternative models. We then Ðnd a factor of 1.3 for the global uncertainty on the Comptonization parameter. Combining the SZ and the X-ray measurements, we determine a value for the Hubble constant. The 2 mm data are consistent with km s~1 Mpc~1, where the H 0 (q 0 \ 1 2 ) \ 53~2 8 38 uncertainty is dominated by the uncertainty in the models of the X-ray plasma halo.

COMPASS is an on-axis 2.6 m telescope coupled to a correlation polarimeter operating at a wavelength of 1 cm. The entire instrument was built specifically for cosmic microwave background (CMB) polarization studies. We report here on observations of 2001 February-April using this system. We set an upper limit on E-mode polarized anisotropies of 1036 K 2 (95% confidence limit) in the l range 93-555. Subject headingg s: cosmic microwave background -cosmology: observations -instrumentation: polarimeters On-line material: color figures A

A critical review is presented of the observations of the Cosmic Background spectrum and anisotropies. Some cosmological impltcations are discussed and future programs are Illustrated.