Infrared Digital Spectrograph for Hydroxyl Rotational Temperature Measurements

A digital spectrograph designed for registration of nightglow intensity variations and estimation of the atmospheric temperature by the rotational structure of the hydroxyl emission luminosity is described. The spectrograph is based on an MДP-2 monochromator and an ST-6 CCD detector. The instrument records the nightglow spectrum in a wavelength range of 800–1000 nm, in which strong molecular hydroxyl (OH) bands emitted at the mesopause height (∼87 km) are present. The rotational temperature of OH is estimated by the least square fitting of the synthetic spectrum constructed for various temperatures to an experimental one. The temperature measurement errors are 2–10 K.