Fabry-Perot-interferometer imaging system for thermospheric temperature and wind measurements

Doppler-broadened Fabry-Perot fringes of weak (<1-kR) auroral [OI] 5577- and 6300-A emissions have been detected in real time (1/60 sec) with the aid of a low-light level image-orthicon TV camera coupled to a two stage image intensifier. The imaging scheme permits static-mode operation of a Fabry-Perot interferometer. For maximum use of all the information contained in every TV frame, each circular fringe may be sectioned into several annuli, and the corresponding annuli from all rings are summed to yield an intensity value. This procedure for deriving a fringe profile requires a video digitizer coupled to a digital processing system and should provide fast real-time (1/60 sec) measurements of E- and F-region temperatures and winds. A more restricted analysis of the TV images involves analog display of the intensity distribution along a few raster lines. Since only a minute fraction of the total signal is thus utilized to derive a fringe profile, image integration on the TV camera is necessary to assure high SNR of the profile. With [OI] 5577-A intensity of ~750 R, visually prominent TV images of the Fabry-Perot fringes were recorded in 0.5 sec, and the temperature of the emitting region was determined from ~2% of the total information in the TV image.