First Ground-Based 200-micron Observing with THUMPER on JCMT - Sky Characterisation and Planet Maps

Ward-Thompson, Derek ORCID: https://orcid.org/0000-0003-1140-2761, Ade, Peter A. R. ORCID: https://orcid.org/0000-0002-5127-0401, Araujo, H., Coulson, I., Cox, James, Davis, G. R., Evans, Rhodri, Griffin, Matthew Joseph ORCID: https://orcid.org/0000-0002-0033-177X, Gear, Walter Kieran ORCID: https://orcid.org/0000-0001-6789-6196, Hargrave, Peter Charles ORCID: https://orcid.org/0000-0002-3109-6629, Hargreaves, P., Hayton, Darren John, Kiernan, Brian John, Leeks, Sarah Jane, Mauskopf, Philip Daniel ORCID: https://orcid.org/0000-0001-6397-5516, Naylor, D., Potter, N., Rinehart, S. A., Sudiwala, Rashmikant V. ORCID: https://orcid.org/0000-0003-3240-5304, Tucker, Charles Robert, Walker, R. J. and Watkin, Steven Lloyd 2005. First Ground-Based 200-micron Observing with THUMPER on JCMT - Sky Characterisation and Planet Maps. Monthly Notices of the Royal Astronomical Society 364 , pp. 843-848. 10.1111/j.1365-2966.2005.09625.x

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Abstract

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 ?m (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, ?, at 1.5 THz and that at 225 GHz: ?1.5 THz= (95 ± 10) ×?225 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 (1? 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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Uncontrolled Keywords:	instrumentation: photometers; techniques: photometric; infrared: Solar system; submillimetre
ISSN:	0035-8711
Last Modified:	05 Jan 2024 03:09
URI:	https://orca.cardiff.ac.uk/id/eprint/1649

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