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Session 48 - Workshop on the Future of Antarctic Astrophysics - I.
Topical, Oral session, Wednesday, June 10

[48.06] Atmospheric transparency at 350\thinspace \mum wavelength

S. J. E. Radford, M. A. Holdaway (NRAO), J. B. Peterson (CMU)

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.

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