An application of a michelson interferometer to measurements of OH rotational temperatures

The Polar Research Center, Korea Ocean R & D Institute, recently equipped a Michelson interferometer to study the Earth's upper atmospheric region as a complement to a Fabry-Perot interferometer which had already been used for thermospheric study. This Michelson interferometer was used to observe terrestrial nightglow (Meinel bands) emitted by hydroxyl (OH) radicals in the upper mesosphere. Altitude profiles of the Meinel bands obtained by rocket-borne photometers and satellite-borne instruments place the peak emission near 87 km. Rotational relaxation is sufficiently rapid in this region so that the distribution of rotational lines within a band represents the kinetic temperature of the gas. Nightglow spectra were observed at Ansan, Korea, and were used to retrieve the rotational temperatures, as well as the band intensities, of the OH molecules in the upper mesosphere. The observed upper mesospheric temperatures were in the range of 160̃210 K with uncertainties of less then 7 K.