In-Flight Performance of the ICON EUV Spectrograph.

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.

Design and Performance of the ICON EUV Spectrograph.

We present the design, implementation, and on-ground performance measurements of the Ionospheric Connection Explorer EUV spectrometer, ICON EUV, a wide field (17° x 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 Oil emission lines at 61.6 nm and 83.4 nm. Its design, using a single optical element, permits a 0°.26 imaging resolution perpendicular to the spectral dispersion direction with a large (12°) acceptance parallel to the dispersion direction while providing a slit-width dominated spectral resolution of R ~ 25 at 58.4 nm. Pre-flight calibration shows that the instrument has met all of the science performance requirements.

Microchannel Plate Imaging Photon Counters for Ultraviolet through NIR Detection with High Time Resolution.

Cross strip and cross delay line readout microchannel plate detectors in 18 mm, 25 mm and 40 mm active area formats including open face (UV/particle) and sealed tube (optical) configurations have been constructed. These have been tested with a field programmable gate array based electronics for single event encoding. Using small pore MCPs (6 µm) operated in a pair, we achieve gains of >1 × 106 which is sufficient to provide spatial resolution of ~17 µm FHWM with the 18 mm and 40 mm cross strip readouts. New cross strip electronics can process high output event rates (> 4 MHz) with high spatial resolution, and self triggered event timing accuracy of ~1.5 ns for sealed tube XS optical sensors. A peak quantum efficiency of between 13% and 19% at 500 nm has been achieved with SuperGenII photocathodes with response from 400 nm to 900 nm for both cross strip and cross delay line sealed tubes. Local area counting rates of up to 40 kHz (100µm spot) have been attained with XS sealed tubes, along with image linearity and stability to better than 50 µm. 25mm cross delay line tubes achieve ~50 µm resolution and > 2 MHz output event rates.