A large-aperture high-resolution Fabry-Perot spectrometer for airglow studies

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Abstract
A scanning Fabry-Perot interferometer with 150 mm diameter plates has been built for use in spectral studies of faint atmospheric radiations. The instrument has been designed for usefulness over a wide region of the visible spectrum and at different spectral resolutions; the reflective plate coatings are a metal-dielectric combination, and plate separation can be varied easily over several centimetres. Scanning is achieved through piezoelectric plate spacing elements. Both plate parallelism and plate separation are servocontrolled, the latter with the aid of a highly linear and stable capacitive displacement transducer which directly measures changes in plate separation. Photoelectric detection and digital signal averaging and recording are used. The spectrometer has been applied to the study of winds and temperatures in the upper atmosphere through the measurement of Doppler line shift and broadening in airglow emission lines.