A novel infrared imager for studies of hydroxyl and oxygen nightglow emissions in the mesopause above northern Scandinavia

Abstract. The paper describes technical characteristics and presents first scientific results of a novel infrared imaging system (imager) for studies of nightglow emissions coming from hydroxyl (OH) and molecular oxygen (O₂) layers in the mesopause region (80–100 km) above northern Scandinavia. The OH imager was put into operation in November 2022 at the Swedish Institute of Space Physics located in Kiruna (67.86° N, 20.42° E, 400 m altitude). The OH imager records selected emission lines in the OH (3-1) band near 1500 nm to obtain intensity and temperature maps at around 87 km altitude. Also, the OH imager registers infrared emissions coming from the O₂ IR A-band airglow at 1268.7 nm in order to obtain O₂ intensity maps at a slightly higher altitude around 94 km. This technique allows tracing wave disturbances both in horizontal and vertical domains in the mesopause region. Validation and comparison of the OH (3-1) rotational temperature with collocated lidar and Aura/MLS satellite temperatures are performed. First scientific results obtained with the OH imager for the first winter season (2022–2023) are discussed.