FTS measurements of submillimeter opacity and other site testing at Pampa la Bola

Satoki Matsushita; Hiroshi Matsuo; Akihiro Sakamoto; Juan R. Pardo

doi:10.1117/12.390432

3 July 2000 FTS measurements of submillimeter opacity and other site testing at Pampa la Bola

Satoki Matsushita, Hiroshi Matsuo, Akihiro Sakamoto, Juan R. Pardo

Proceedings Volume 4015, Radio Telescopes; (2000) https://doi.org/10.1117/12.390432
Event: Astronomical Telescopes and Instrumentation, 2000, Munich, Germany

Abstract

We have carried out Fourier Transform Spectrometer (FTS) measurements of the millimeter and submillimeter-wave (150 - 1500 GHz or 2 mm - 200 micrometer) atmospheric opacity at Pampa la Bola, 4800 m above sea level in northern Chile on September 1997 and June 1998. One of the best transmission spectra show up to approximately 67% transmission at well- known submillimeter-wave windows. Supra-terahertz windows (located around 1035 GHz, 1350 GHz, and 1500 GHz) were identified in the same spectrum. The observed spectra can be well modeled by newly developed radiative-transfer calculations. Correlations between 220 GHz opacities and those of the center of submillimeter-wave windows or even those of the supra-terahertz windows are obtained using the entire data set. Good correlations were obtained except for the periods affected by the liquid water opacity component. We succeeded to separate the total opacity in two parts: the water vapor opacity and the liquid water opacity, using two frequencies, one in the millimeter domain and another one in the submillimeter. The separated water vapor opacity component shows good correlation with the 183 GHz pure water vapor line opacity which is also covered in the measured spectra, but the liquid water opacity component shows no correlation. The liquid water opacity component also shows no correlation with the phase fluctuation measured with the 11 GHz radio seeing monitor. Modeling of this component is currently under way. Combined with a statistical study of the 225 GHz opacity data of the Chajnantor site (approximately 7 km apart from Pampa la Bola), it is estimated that submillimeter-wave observations can be done with zenith opacity less than 1.0 (at the most transparent frequency in those windows) for about 50% of the winter season, assuming no presence of liquid water absorption.

Citation Download Citation

Satoki Matsushita, Hiroshi Matsuo, Akihiro Sakamoto, and Juan R. Pardo "FTS measurements of submillimeter opacity and other site testing at Pampa la Bola", Proc. SPIE 4015, Radio Telescopes, (3 July 2000); https://doi.org/10.1117/12.390432

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