Satellite limb tomography applied to airglow of the 630 nm emission

Airglow intensity variations in the 90 km altitude range are generally inte rpreted as the optical signature of gravity waves propagating through the a irglow layer. In contrast, modulations of the 630 nm emission in the F regi on are subject to atmospheric wave propagation and ionospheric electrodynam ics, which makes it difficult to determine the dominating process. Spacecra ft-based imaging of the 630 nm airglow could produce global data of airglow modulations greatly needed for the understanding of thermospheric dynamics . Observations of the thick 630 nm airglow layer between 200 and 300 km alt itude are used to demonstrate the ability to tomographically retrieve the m odulated volume emission rates from limb observations from a spacecraft. An algebraic reconstruction technique is used to obtain vertical and horizont al distributions with average errors of 20%. Its effectiveness is demonstra ted by simulations with numerical data. Forward limb observations in the 63 0 nm range strongly reduce the angular range and limit the measurement scal e to 300 km. These results are obtained without any assumptions about the o riginal distribution other than nonnegativity. The overall computational ef fort would allow the analysis of a large number of observations as provided by global survey experiments.