MAHRSI observations of nitric oxide in the mesosphere and lower thermosphere

Abstract

In November, 1994, the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) observed the distribution of NO between the altitudes of 76 and 140 km by measuring limb intensity profiles of solar resonance fluorescence in the NO A ²Σ → X ²II (1,0) γ band near 215 nm. The observations were made from the ASTRO‐SPAS (Shuttle Pallet Satellite) spacecraft which was deployed and retrieved by the space shuttle. The data provided a seven hour snapshot of lower thermospheric and mesospheric NO from sunrise near 48°S to sunset near 61° N latitude following a period of low solar and high geomagnetic activity. Inferred peak lower thermospheric NO densities ranged from 3 × 107 cm−3 near the equator to 2 × 108 cm−3 at high northern latitudes, roughly consistent with previous observations for the same conditions. Individual vertical density profiles showed substantial structure and large orbit to orbit variations, suggesting that the distribution of mesospheric and lower thermospheric NO is dynamically influenced.