Abstract
Since the earliest space-based observations of Earth’s atmosphere,
ultraviolet (UV) airglow has proven a useful resource for remote sensing
of the ionosphere and thermosphere. The NASA Ionospheric Connection
Explorer (ICON) spacecraft, whose mission is to explore the connections
between ionosphere and thermosphere utilizes UV airglow in the typical
way: an extreme-UV (EUV) spectrometer uses dayglow between 54 nm and 88
nm to measure the density of O+, and a far-UV spectrograph uses the O
135.6 nm doublet and N2 Lyman-Birge-Hopfield band dayglow to measure the
column ratio of O to N2 in the upper thermosphere. Two EUV emission
features, O+ 61.6 nm and 83.4 nm, are used for the O+ retrieval;
however, many other features are captured along the EUV instrument’s
spectral dimension. In this study, we examine the other dayglow features
observed by ICON EUV and demonstrate that it measures a nitrogen feature
around 87.8 nm which can be used to observe the neutral thermosphere.