<title>CSO-JCMT Interferometer and 183-GHz radiometric phase correction</title>

Abstract

The Caltech Submillimeter Observatory and the James Clerk Maxwell Telescope have been combined to form the only astronomical interferometer currently operating at submillimeter wavelengths. The telescopes have been operating in this mode for one or two dedicated periods in each of the last 5 years. Results with sub-arcsecond resolution have been obtained at 230, 345 and 460 GHz. The interferometer differs in many ways from the existing millimeter-wave arrays. Connecting two independent telescopes of different design introduces extra problems not encountered with homogeneous arrays of antennas. The CSO-JCMT system is described, with an emphasis on these incompatibility issues and solutions that were adopted. Analysis of data from a single, fixed baseline requires direct modeling of the measured visibilities rather than a synthesized image, an approach that has since proved invaluable for analyzing data from other arrays as well. The sensitivity and angular resolution of the interferometer are limited by fluctuations in the refractive index due to water vapor in the Earth's atmosphere. Two water vapor radiometers have been designed, built and installed to monitor the fluctuations in each beam and generate a correction to the visibility phase measured by the interferometer. These radiometers are described and recent results are presented.