Cryogenic Fourier spectrometer for measuring trace species in the lower stratosphere

A cryogenic Fourier transform spectrometer has been built to measure thermal emission of the earth's limb from a balloon-borne platform. Liquid nitrogen cooling of the spectrometer and liquid helium cooling of the detectors has provided sufficient sensitivity to detect, at 5-15 microns, fifteen molecular species relevant to stratospheric ozone chemistry. The spectral resolution achieved, 0.022/cm, is the best yet attained for emission mode data at these wavelengths. The philosophy behind the design of the optical and electronic systems is presented, followed by an analysis of the performance achieved during balloon flight.