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.