Measurements of Atmospheric Water Vapor Above Mauna Kea Using an Infrared Radiometer

This paper presents the first results from a prototype infrared radiometer which has been developed to measure variations in atmospheric water vapor column abundance from high altitude sites. The performance of the infrared radiometer is compared and contrasted with that of a water vapor monitor operating at radio frequencies. Analysis shows that the infrared radiometer can measure variations at the level of 1 m precipitable water vapor (pwv) in an integration time of 1 s when the total column abundance is 0.5 mm pwv. Since variations in atmospheric water vapor are the dominant source of phase noise in (sub)millimeter astronomical interferometry, an instrument capable of rapid and high sensitivity water vapor measurements has the potential to provide the necessary phase correction information for interferometric arrays.