Mesospheric infrared airglow measurements of molecular twilight transitions by means of satellite-based radiometry

Characterizations of twilight mesospheric hydroxyl volume emission rate (VER), and molecular ozone mixing ratio from year 2002 to 2005, are made possible using SABER (Sounding of the Atmosphere using Broadband Emission Radiometry), a 10-channel infrared radiometer onboard NASA's TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite. During sunset SABER radiometric channel 9, centered at lambda = 1.64 mum for OH (5,3) and OH (4,2) Meinel band airglow transitions, exhibited average rise times of 0.96 hours for near-equatorial latitudes. SABER channel 8, at lambda = 2.06 mum for OH (9,7) and OH (8,6) transitions, showed average rise times of 1.00 hours. SABER channel 4 for molecular ozone airglow centered at lambda = 9.3 mum exhibited rise times of 1.25 hours. Correlations between binned channel VER/mixing ratio data show temporal patterns of hydroxyl and ozone dependencies which correlate to equinox and solstice events. Annual averages show faster rise rates during sunset transitions at near-equatorial latitudes than at midlatitudes for each of the bands analyzed. Slower transition fall rates were observed at sunrise near the equator for the hydroxyl bands when compared with rates at midlatitudes.