[Previous] | [Session 121] | [Next]
S. J. E. Radford (NRAO), ALMA Site Characterization Team
Conditions for observing with the ALMA at Chajnantor
The international Atacama Large Millimeter Array will be constructed on the high (5050 m) plateau southwest of Cerro Chajnantor, Chile, about 40 km east of the village of San Pedro de Atacama. Starting in 1995 April, the ALMA project has deployed an extensive suite of instruments to characterize atmospheric conditions at These instruments include a 225 GHz tipping radiometer to measures atmospheric transparency and temporal emission fluctuations, two 11 GHz interferometers to measure atmospheric phase fluctuations, two 183 GHz line radiometers to measure the water vapor content and test techniques to compensate for phase fluctutations, a submillimeter tipping photometer to measure the atmospheric transparency at 350 \mum wavelength, radiosonde launches, a precision hygrometer, and other meteorolgical instruments. Submillimeter Fourier transform spectrometers have also been operated at Chajnantor.
These measurements since have demonstrated Chajnantor is a premier site for observations at millimeter and submillimeter wavelengths, with exceptional atmospheric conditions. In comparison to other observatory locations, the atmospheric transparency and phase stability at Chajnantor are better more often than at Mauna Kea and the transparency is competitive with the South Pole. At Chajnantor, the best conditions occur early in the morning during the winter. There are significant correlations between several of the meteorological parameters, in particular the transparency and the phase stability.
The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
[Previous] | [Session 121] | [Next]
Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.