Pressure-scanned Fabry-Perot Spectrometer for Night Airglow Studies

Abstract

The paper describes a pressure-scanned Fabry-Perot spectrometer designed for the line-profile studies of night airglow emission lines. An important feature of the equipment is the photon counting detection which is synchronized with pressure changes in discrete steps, each step corresponding to 0'0014 Ǻ of a spectral scan at 6300 Ǻ. The design also permits repetitive scanning over the same fringe in order to achieve improvement in signal-to-noise ratio when observing a weak emission line. Line profiles of 6300 Ǻ O(I) night airglow emissions were recorded for a few nights from Mt. Abu during Dec. 1974. The instrument profile was obtained by recording the He-Ne 6328 Ǻ laser line. The observed line profiles of 6300 Ǻ O (I) lines were corrected for the instrumental broadening by deconvoluting the latter using Fourier transforms. Preliminary Doppler-width temperatures inferred are in fair agreement with Jacchia (1971) model atmospheric temperature.