SAFIRE-A: Spectroscopy of the atmosphere using far-infrared emission/airborne

A new instrument named SAFIRE-A (Spectroscopy of the Atmosphere using Far-I nfrared Emission/Airborne), which can operate on high-altitude platforms, h as been developed for the study of the atmospheric composition through limb -scanning emission measurements. The instrument is a polarizing Fourier tra nsform spectrometer that operates in the far infrared with a resolution of 0.004 cm(-1). SAFIRE-A uses efficient photon noise limited detectors and a novel optical configuration, which provide a cold pupil and field stop as w ell as cold narrow bandpass filters to enhance its sensitivity. The instrum ent was successfully operated on an M-55 stratospheric research aircraft in the polar regions during the winter 1996-97 Airborne Polar Experiment. The instrument design, aircraft integration, and performances attained in the field campaign are described and discussed. The atmospheric emission spectr um is measured with an rms noise accuracy of 0.5 K (measured in brightness temperature) in each spectral element near 20 cm(-1) with a 30-s measuremen t time.