Extended-field large-aperture interferometer-spectrometer for airglow surveys.

The design of a field-of-view-widened interferometer for airglow survey work is discussed, and some preliminary airglow results are presented. The 4.5-cm aperture optics of the interferometer give a very large throughput gain compared with a conventional slit spectrometer. In addition, by using optical wedge compensators, the field of view is widened to over 5 degrees full angle, resulting in a field-widened throughput gain of approximately 100 compared with a standard Michelson interferometer of the same aperture size. Digital recording is used to achieve sufficient dynamic range and to aid in computation of the fast fourier transforms. A series of airglow spectra of the midlatitude sky in the spectral region from 0.6 micro to 0.9 micro down to a resolution of about 2 A are given for a sunset transition and also at night. Bright features are the vibration-rotation hydroxyl emission bands and the oxygen red lines. Particularly interesting are enhancement of these emissions during twilight and the observation of what may be vibrationally excited O(2) in the lower atmosphere.