A Fourier transform spectrometer for measurement of atmospheric transmission at submillimeter wavelengths

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