Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) On-Orbit Wind Observations: Data Analysis and Instrument Performance

Abstract

The design, principles of operation, calibration, and data analysis approaches of the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) on the NASA Ionospheric Connection (ICON) satellite have been documented prior to the ICON launch. Here we update and expand on the MIGHTI wind data analysis and discuss the on-orbit instrument performance. In particular, we show typical raw data and we describe key processing steps, including the correction of a “signal-intensity dependent phase shift,” which is necessitated by unexpected detector behavior. We describe a new zero-wind calibration approach that is preferred over the originally planned approach due to its higher precision. Similar to the original approach, the new approach is independent of any a priori data. A detailed update on the wind uncertainties is provided and compared to the mission requirements, showing that MIGHTI has met the ICON mission requirements. While MIGHTI observations are not required to produce absolute airglow brightness profiles, we describe a relative brightness profile product, which is included in the published data. We briefly review the spatial resolution of the MIGHTI wind data in addition to the data coverage and data gaps that occurred during the nominal mission. Finally, we include comparisons of the MIGHTI wind data with ground-based Fabry-Perot interferometer observations and meteor radar observations, updating previous studies with more recent data, again showing good agreement. The data processing steps covered in this work and all the derived wind data correspond to the MIGHTI data release Version 5 (v05).

Monthly Climatologies of Zonal‐Mean and Tidal Winds in the Thermosphere as Observed by ICON/MIGHTI During April 2020–March 2022

“…As previous studies have discussed (e.g., Englert et al., 2023), it takes longer than a month (48 days) for ICON/MIGHTI to achieve full local‐time coverage at all latitudes. Despite that, our method described above allows to determine tides for each month for the following reasons.…”

“…Thus, it was previously difficult to obtain reliable climatological estimates of zonal‐mean winds and tides. The v05 data avoids this issue by the use of a renewed baseline calibration technique (Englert et al., 2023).…”

“…The v05 ICON/MIGHTI wind data (level 2.2, cardinal vector winds) during the 24‐month period from April 2020 to March 2022 are analyzed to determine zonal‐mean winds and tides. The estimated accuracy of the v05 wind data is generally 10–25 m/s (Englert et al., 2023). Only the data that are flagged as “Good” (Wind_Quality = 1 are used.…”

“…This issue was described in detail by Englert et al. (2023). The baseline drift was found to be dependent on the local time and height, which has made the reliable assessment of zonal‐mean winds and tides difficult.…”

“…Version 5 (v05) of the ICON/MIGHTI wind data has been recently (in November 2022) released. A new calibration method for the so‐called “zero wind” has been developed for v05, which uses a long‐term (96 days) comparison of the ascending‐ and descending‐orbit data to perform a self‐calibration of the zero baseline, independent of external data or models (Englert et al., 2023). The present study evaluates, for the first time, zonal‐mean winds and tides using the v05 ICON/MIGHTI wind data for the height ranges of 90–110 and 200–300 km, where wind measurements are made during both day and night.…”