PROBA2 LYRA Occultations: Thermospheric Temperature and Composition, Sensitivity to EUV Forcing and Comparisons with Mars

Abstract

A method is presented for retrieving temperature and composition from 150-350 km in Earth's thermosphere using total number density measurements made via EUV solar occultations by the PROBA2/LYRA instrument. Systematic and random uncertainties are calculated and found to be less than 5% for the temperature measurements and 5-20% for the composition measurements. Regression coefficients relating both temperature and the [O]/[N2] abundance ratio with EUV irradiance at