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Session 48 - Workshop on the Future of Antarctic Astrophysics - I.
Topical, Oral session, Wednesday, June 10
Presidio,
Comparative measurements of atmospheric transparency are underway at three sites of current or proposed telescopes for submillimeter wavelength astronomy: the South Pole (2835\thinspace m), Mauna Kea (CSO, 4070\thinspace m), and Chajnantor, Chile (5000\thinspace m). At each site, the transparency is determined from the sky brightness measured by a broadband tipping photometer about four times per hour. These instruments are based on ambient temperature pyroelectric detectors and have resonant metal mesh filters that define a passband matched to the 350\thinspace \mum atmospheric window. Two internal loads are used to calibrate the detector response. The instrument on Mauna Kea is being cross calibrated against a 225\thinspace GHz tipping radiometer, 808--846\thinspace GHz heterodyne measurements (CSO), 350\thinspace \mum broadband (SCUBA on JCMT) measurements, and broadband spectroscopy (FTS on CSO). On Chajnantor, the tipping photometer is cross calibrated against a 225 GHz tipping radiometer and a broadband spectrometer (FTS). Cumulative distributions of the measured zenith optical depth indicate the amount of time at these sites suitable for submillimeter wavelength observations.
The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
