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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.