2005/09/22 by D. Ward-Thompson, D. Ward–Thompson, P. A. R. Ade +32
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Atmospheric Ozone and Climate #Spectroscopy and Laser Applications #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2005.09625.x
published as Mon.Not.Roy.Astron.Soc.364:843-848,2005 · 7 pages, 8 figures, accepted by MNRAS
arxiv created 2005/09/22 · openalex publication_date 2005/11/03 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/29
We present observations that were carried out with the Two HUndred Micron PhotometER (THUMPER) mounted on the James Clerk Maxwell Telescope (JCMT) in Hawaii, at a wavelength of 200 μm (frequency 1.5 THz). The observations utilize a small atmospheric window that opens up at this wavelength under very dry conditions at high-altitude observing sites. The atmosphere was calibrated using the sky-dipping method and a relation was established between the optical depth, τ, at 1.5 THz and that at 225 GHz: τ1.5 THz= (95 ± 10) ×τ225 GHz. Mars and Jupiter were mapped from the ground at this wavelength for the first time, and the system characteristics measured. A noise-equivalent flux density (NEFD) of ∼ 65 ± 10 Jy (1σ 1s) was measured for the THUMPER-JCMT combination, consistent with predictions based upon our laboratory measurements. The main beam resolution of 14 arcsec was confirmed and an extended error beam detected at roughly two-thirds of the magnitude of the main beam. Measurements of the Sun allow us to estimate that the fraction of the power in the main beam is ∼15 per cent, consistent with predictions based on modelling the dish surface accuracy. It is therefore shown that the sky over Mauna Kea is suitable for astronomy at this wavelength under the best conditions. However, higher or drier sites should have a larger number of useable nights per year.