RESUMO
We present in-flight performance measurements of the Ionospheric Connection Explorer EUV spectrometer, ICON EUV, a wide field ( 17 ∘ × 12 ∘ ) extreme ultraviolet (EUV) imaging spectrograph designed to observe the lower ionosphere at tangent altitudes between 100 and 500 km. The primary targets of the spectrometer, which has a spectral range of 54-88 nm, are the Oii emission lines at 61.6 nmand 83.4 nm. In flight calibration and performance measurement has shown that the instrument has met all of the science performance requirements. We discuss the observed and expected changes in the instrument performance due to microchannel plate charge depletion, and how these changes were tracked over the first two years of flight. This paper shows raw data products from this instrument. A parallel paper (Stephan et al. in Space Sci. Rev. 218:63, 2022) in this volume discusses the use of these raw products to determine O+ density profiles versus altitude.
RESUMO
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 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 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.