Swarm Thermal Ion Imager measurement performance

Abstract

We assess the performance of the thermal ion imaging (TII) technique as conceived for the Swarm Earth Explorer satellites. Analysis, simulation, and laboratory testing performed prior to flight provided estimates of systematic and random error sources of the electric field instrument’s vector ion drift, electric field, and ion kinetic temperature measurements. An end-to-end instrument simulator, consisting of models of the TIIs on a prototypical Swarm satellite orbiting Earth with ionospheric plasma, electric field, and magnetic field inputs, was used to generate TII sensor data (level 0 instrument data). These data were processed with a prototype processor (the level 1b processor) to characterize theoretical measurement performance. We describe the methodology used to assess TII measurement uncertainty and present the main findings of the end-to-end measurement performance study. In addition, we assess the measurement performance achieved during approximately eight years of orbital operations. Example measurements demonstrate the quality of ion drift velocity. Unprocessed TII imagery reveals spurious signals which can affect measurement performance. Availability of such imagery has proven vital for diagnosing measurement anomalies associated with sensor operation and spacecraft–plasma interactions. Graphical Abstract

Calibration of Swarm Ion Density, Drift, and Effective Mass Measurements

“…There are other processes to consider, like those related to photoelectrons, both of satellite and ionospheric origins, energetic particle precipitation, magnetic field, surface chemistry and aging of components exposed to plasma and sunlight, as well as non‐OML satellite‐plasma interactions, that perhaps are not identified in the calibrations because of potentially large uncertainties in the parametric inputs like electron temperature and satellite floating potential. The biases in ion drift of order 100 m/s can be removed using the approach already used by SLIDEM based on detrending the high‐latitude flows (e.g., Burchill & Knudsen, 2022; Pakhotin et al., 2022).…”

Multi‐Scale Ionospheric Poynting Fluxes Using Ground and Space‐Based Observations

“…However, it minimizes avoidable errors in the Swarm electric field for the purpose of comparisons with SuperDARN convection patterns. Previous studies have carried out comprehensive validations of the ion‐drifts from Swarm, including comparisons with those from SuperDARN (Burchill & Knudsen, 2022; Fiori et al., 2016; Koustov et al., 2019; Lomidze et al., 2019).…”