Application of a dual Fabry-Perot spectrometer for daytime airglow studies.

A scanning spectrometer comprising a large, high resolution Fabry-Perot etalon, a small, low resolution etalon and an interference filter is briefly described. Its application to the recording of atomic spectral line emissions from the daytime upper atmosphere is discussed. The major difficulty is that of discriminating against the very high intensity of scattered sunlight, the spectrum of which is complex and varies significantly during the course of an observation. The performance achieved is adequate to permit useful information on upper atmosphere temperature and wind velocity to be inferred from Doppler broadening and shift of recorded line profiles.