MMA Memo #187

Modeling of the Submillimeter Opacity on Chajnantor

M.A. Holdaway [1], Juan R. Pardo [2]

October 17, 1997

Keywords: submillimeter opacity, Chajnantor, site testing

We have found two errors in NRAO's version of the Liebe 1989 atmospheric transmission model. These errors resulted in opacities at the Chajnantor site in the 650 and 850~GHz windows which were a factor of two lower than the corrected model or the Liebe 1993 predict. However, the Hills data set of 225 and 692~GHz opacities from Mauna Kea agrees with the old, buggy NRAO version of Liebe 1989, and not with any models which we now believe to be correct. This ambiguous situation requires more data from the Chajnantor site, but we should also be prepared for higher submillimeter opacities than those in the MMA project had been suggesting. Even so, Chajnantor should be a much better submillimeter site than Mauna Kea, due to the lower precipitable water vapor as inferred from the 225~GHz opacities.

[1] NRAO
[2] NASA Goddard and DEMIRM Observatoire de Paris

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Last modified: 09 December, 1999