Preparing a 20µm water vapour monitor (IRMA) for operations at Dome C

• Main Authors: Phillips, R. R., Naylor, D. A., Knee, L. B., Dahl, R. E., Sirbu, D.
• Format: Article in Journal/Newspaper
• Language: English
• Subjects: Antarctic; Gemini; Antarc*; Antarctica
• Online Access: https://nrc-publications.canada.ca/eng/view/object/?id=4da56647-5b19-4a41-bc93-46658fa425c9; https://nrc-publications.canada.ca/fra/voir/objet/?id=4da56647-5b19-4a41-bc93-46658fa425c9

The Infrared Radiometer for Millimetre Astronomy (IRMA) is a compact, relatively low cost, 20 µm water vapour monitor. By carefully choosing a 2 µm band that contains only water vapour molecule transitions it is possible to use a simple infrared detector chip to measure the total flux emitted by a column of atmosphere and hence, via an atmospheric model, to determine the total precipitable water vapour. Since February 2005, an IRMA has been measuring precipitable water vapour levels in Chile at the Gemini South site on Cerro Pachon with a second unit added at the nearby Las Campanas observatories site in August 2005. In early 2006 data collection started with three new build IRMA units at three locations for the Thirty Meter Telescope (TMT) project site testing effort. Additionally, an IRMA unit is in the process of being modified to prepare it for operations at Dome C in Antarctica as an addition to the suite of instruments on the University of New South Wales' AASTINO site monitoring facility. We present here a description of the features of the TMT IRMA units that enable them to run in a remote, unattended location in the Chilean desert that are relevant to the similarly remote Dome C operations. In addition we describe the modifications that have been undertaken and that are currently being tested in order to enable the units to operate with minimal redesign at the extremely low Antarctic winter temperatures. Peer reviewed: Yes NRC publication: Yes