Far infrared spectrometry of the cosmic background radiation

Two experiments to measure the cosmic background radiation near 1 mm wavelength are described. The first was a ground-based search for spectral lines, made with a Fabry--Perot interferometer and an InSb detector. The second is a measurement of the spectrum from 3 to 18 cm-1, made with a balloon-borne Fourier transform spectrometer. It is a polarizing Michelson interferometer, cooled in liquid helium, and operated with a germanium bolometer. The theory of operation, construction details, and experimental results is given. The first experiment was successfully completed but the second suffered equipment malfunction on its first flight. The theory of Fourier transformations is described and a new understanding of convolutional phase correction computations is given. Far infrared bolometer calibration procedures are discussed and test results on nine detectors are tabulated. Methods of improving bolometer sensitivity with immersion optics and with conductive film blackening are described