Browsing by Author "Meier, R. R."

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    In Flight Performance of the Far Ultraviolet Instrument (FUV) on ICON
    Frey, H. U.; Mende, S. B.; Meier, R. R.; Kamaci, U.; Urco, J. M.; Kamalabadi, F.; England, Scott L.; Immel, T. J. (Springer, 2023-04)
    The NASA Ionospheric Connection Explorer (ICON) was launched in October 2019 and has been observing the upper atmosphere and ionosphere to understand the sources of their strong variability, to understand the energy and momentum transfer, and to determine how the solar wind and magnetospheric effects modify the internally-driven atmosphere-space system. The Far Ultraviolet Instrument (FUV) supports these goals by observing the ultraviolet airglow in day and night, determining the atmospheric and ionospheric composition and density distribution. Based on the combination of ground calibration and flight data, this paper describes how major instrument parameters have been verified or refined since launch, how science data are collected, and how the instrument has performed over the first 3 years of the science mission. It also provides a brief summary of science results obtained so far.
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    Reducing the Ionospheric Contamination Effects on the Column O/N-2 Ratio and Its Application to the Identification of Non-Migrating Tides
    Krier, Christopher S.; England, Scott L.; Meier, R. R.; Frey, Harald U. (American Geophysical Union, 2023-04)
    Prior investigations have attempted to characterize the longitudinal variability of the column number density ratio of atomic oxygen to molecular nitrogen (SO/N-2) in the context of non-migrating tides. The retrieval of thermospheric SO/N-2 from far ultra-violet (FUV) emissions assumes production is due to photoelectron impact excitation on O and N-2. Consequently, efforts to characterize the tidal variability in SO/N-2 have been limited by ionospheric contamination from O+ + e radiative recombination at afternoon local times (LT) around the equatorial ionization anomaly. The retrieval of SO/N-2 from FUV observations by the Ionospheric Connection Explorer (ICON) provides an opportunity to address this limitation. In this work, we derive modified SO/N-2 datasets to delineate the response of thermospheric composition to non-migrating tides as a function of LT in the absence of ionospheric contamination. We assess estimates of the ionospheric contribution to 135.6 nm emission intensities based on either Global Ionospheric Specification (GIS) electron density, International Reference Ionosphere (IRI) model output, or observations from the Extreme Ultra-Violet imager (EUV) onboard ICON during March and September equinox conditions in 2020. Our approach accounts for any biases between the ionospheric and airglow datasets. We found that the ICON-FUV data set, corrected for ionospheric contamination based on GIS, uncovered a previously obscured diurnal eastward wavenumber 2 tide in a longitudinal wavenumber 3 pattern at March equinox in 2020. This finding demonstrates not only the necessity of correcting for ionospheric contamination of the FUV signals but also the utility of using GIS for the correction.