In Flight Performance of the Far Ultraviolet Instrument (FUV) on ICON

Abstract

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.

Using ICON Satellite Data to Forecast Equatorial Ionospheric Instability Throughout 2022

“…Examining the false negatives more closely and considering the possible role of the shape of the electron number density profile on the predictions, we consider also level-1 data from the ICON FUV instrument (version 5) which measures 135.6 nm OI emissions from the recombination of O + ions in limb profiles in the magnetic meridian at night (Frey et al, 2023). The forward model for the limb profiles (column emissions in Rayleighs vs. tangent ray height) was given by Qin et al (2015) and Kamalabadi et al (2018).…”

Update of ICON-FUV hmF2 and NmF2 Comparison with External Radio Observations

“…During nighttime, only the 135.6 nm channel is used and the level-1 calibrated images are inverted to produce six limb profiles at an observation cadence of 12 s, constituting the level-2 data product 2.5 (DP 2.5). Conversion from raw counts to level-1 radiances is a very important step of the data processing leading to DP 2.5 and we refer to Frey et al (2023) for more details concerning the methodology.…”

“…The network takes as input a 6 × 256 array where the 256-pixel altitude profiles of 6 stripes are all provided at once, and the output is a 6 × 256 array of the star-removed version of the input. • Improved quantitative on-orbit calibration with regular star observations (Frey et al 2023). • The DP 2.5 quality determination algorithm has been updated on version 4 to be more stringent in assigning a quality rating of 1.…”

“…This study was realized during the first year in orbit of ICON and several improvements have been included to the data processing so far, especially at the level-1 processing step with, notably, an improved capability for star detection and removal, a better background subtraction and an advanced code for computing the conjugate photoelectron contribution. A detailed study of Frey et al (2023) (this collection) provides a full description of the FUV instrument and its in-flight performance, especially at the observational and calibration level. In this context, this paper provides an update of the results concerning the comparison, mainly at the peak-level, of O + density profiles provided by ICON-FUV with electron density profiles inferred from COSMIC-2 and ground-based ionosondes.…”

Reducing the Ionospheric Contamination Effects on the Column O/N2 Ratio and Its Application to the Identification of Non‐Migrating Tides

“…Electron density along the line of sight is determined using GIS and IRI output by using the nearest neighbor model grid point. Figure 2 The analysis presented in the following section uses Level 1 Version 3 ICON-FUV data products (calibrated radiances) which are now known to be too high by about 30% (Frey et al, 2023). To account for this and calibrate our calculations of the ionospheric contribution to the emission at 135.6 nm (Equation 1), we determine a scale factor which is applied to the modeled ionospheric emissions.…”