Daytime O/N2 Retrieval Algorithm for the Ionospheric Connection Explorer (ICON)
The NASA Ionospheric Connection Explorer Far-Ultraviolet spectrometer, ICON FUV, will measure altitude profiles of the daytime far-ultraviolet (FUV) OI 135.6 nm and N2 Lyman-Birge-Hopfield (LBH) band emissions that are used to determine thermospheric density profiles and state parameters related to thermospheric composition; specifically the thermospheric column O/N2 ratio (symbolized as \(\Sigma\)O/N2). This paper describes the algorithm concept that has been adapted and updated from one previously applied with success to limb data from the Global Ultraviolet Imager (GUVI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. We also describe the requirements that are imposed on the ICON FUV to measure \(\Sigma\)O/N2 over any 500-km sample in daytime with a precision of better than 8.7%. We present results from orbit-simulation testing that demonstrates that the ICON FUV and our thermospheric composition retrieval algorithm can meet these requirements and provide the measurements necessary to address ICON science objectives.
KeywordsICON Explorer mission Thermosphere Composition Ultraviolet airglow
ICON is supported by NASA’s Explorers Program through contracts NNG12FA45C and NNG12FA42I. We acknowledge the input and feedback from the many scientists who have contributed to the evolution of this work, with specific acknowledgement to the support provided by Douglas P. Drob and J. Michael Picone. RRM thanks the Civil Service Retirement System for partial support.
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