Signal Requirements for Remote IR Limb Sounding of Atomic Oxygen and Temperature in the Thermosphere

Atomic oxygen plays an important role in chemical and collisional processes in the earth's mesosphere and thermosphere. Current techniques, both in situ and remote, for measuring oxygen atom densities in this altitude regime have produced results with unexplained large disparities. We are investigating the feasibility of an approach wherein vertical profiles of translational temperature and oxygen atom density are recovered from measurements of the earth’s limb radiance profile near 147 micrometers and/or 63 micrometers wavelength, corresponding to the OI (3P0-3P1 and 3P1-3P2) transitions of the ground electronic state of atomic oxygen. The assumption that the 3P fine structure levels are in thermodynamic equilibrium (LTE) with the local translational temperature is crucial to the proposed technique, but seems a reasonable one based on the very long radiative lifetimes of the level transitions.