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Proceedings Paper

A water vapour monitor at Paranal Observatory
Author(s): Florian Kerber; Thomas Rose; Arlette Chacón; Omar Cuevas; Harald Czekala; Reinhard Hanuschik; Yazan Momany; Julio Navarrete; Richard R. Querel; Alain Smette; Mario E. van den Ancker; Michel Cure; David A. Naylor
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Paper Abstract

We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO’s Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5 – 9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer’s ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.

Paper Details

Date Published: 24 September 2012
PDF: 12 pages
Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 84463N (24 September 2012); doi: 10.1117/12.924340
Show Author Affiliations
Florian Kerber, European Southern Observatory (Germany)
Thomas Rose, Radiometer Physics GmbH (Germany)
Arlette Chacón, Univ. de Valparaiso (Chile)
Omar Cuevas, Univ. de Valparaiso (Chile)
Harald Czekala, Radiometer Physics GmbH (Germany)
Reinhard Hanuschik, European Southern Observatory (Germany)
Yazan Momany, European Southern Observatory (Chile)
Julio Navarrete, European Southern Observatory (Chile)
Richard R. Querel, Univ. de Chile (Chile)
Alain Smette, European Southern Observatory (Chile)
Mario E. van den Ancker, European Southern Observatory (Germany)
Michel Cure, Univ. de Valparaiso (Chile)
David A. Naylor, Univ. of Lethbridge (Canada)

Published in SPIE Proceedings Vol. 8446:
Ground-based and Airborne Instrumentation for Astronomy IV
Ian S. McLean; Suzanne K. Ramsay; Hideki Takami, Editor(s)

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