D. Cosmo Papa

A Fourier Transform Spectrometer for Measurement of Atmospheric Transmission at Submillimeter Wavelengths

We describe a Fourier transform spectrometer for measurements of atmospheric transmission in the spectral interval 300 GHz to 3.5 THz. This instrument has been developed to evaluate prospective sites for radio astronomical observations at frequencies above 1 THz. Measurements have been made on Mauna Kea, Hawaii, and at the site of the future Millimeter Array near Cerro Chajnantor in northern Chile. Chajnantor frequently exhibits significant transmission in atmospheric windows at frequencies above 1 THz. Here we outline the design and characteristics of the instrument, discuss data processing methods, and present sample measurements from Chajnantor.

An 800 GHz NbN phonon-cooled hot-electron bolometer mixer receiver

We describe a heterodyne receiver developed for astronomical applications to operate in the 350 /spl mu/m atmospheric window. The waveguide receiver employs a superconductive NbN phonon-cooled hot-electron bolometer mixer. The double sideband receiver noise temperature closely follows 1 kGHz/sup -1/ across 780-870 GHz, with the intermediate frequency centered at 1.4 GHz. The conversion loss is about 15 dB. The receiver was installed for operation at the University of Arizona/Max Planck Institute for Radio Astronomy Submillimeter Telescope facility. The instrument was successfully used to conduct test observations of a number of celestial sources in a number of astronomically important spectral lines.

Receiver-beam characterization for the SMA

This paper describes the measurement and subsequent data analysis of the signal beam of the receiver system of the Submillimeter Array (SMA). To measure the receiver beam patterns, a 2-axis planar scanning stage is mounted on top of the receiver assembly. Scanning in a plane orthogonal to the optical path, the near-field measuring system maps out both the amplitude and phase at frequencies of 242 and 265 GHz. By analyzing the measured patterns we can inspect the alignment of an individual receiver, and the optical assembly common to all frequency bands. The data also allows us to determine how the receiver couples to the beam waveguide that feeds the SMA antennas. The measured beam patterns of two different receivers, covering frequency bands of 176 - 256 and 250 - 350 GHz, are presented, as well as the analysis of these data. We believe that this is the first time such a rigorous full vectorial radio alignment technique has been applied to millimeter or submillimeter receiving systems for radio astronomy.