Comparison of TIDI Line of Sight Winds with ICON-MIGHTI Measurements

TL;DR

This study compares TIDI satellite LOS wind measurements with ICON-MIGHTI data, revealing differences in telescope performance and providing metrics to evaluate measurement quality in the mesosphere-lower thermosphere region.

Contribution

It introduces a detailed comparison of TIDI and MIGHTI wind data, highlighting telescope-specific performance variations and establishing figures of merit for measurement quality assessment.

Findings

Coldside telescopes show better correlation with MIGHTI winds.

Tel2 has higher correlation coefficients than Tel1 across conditions.

Performance varies with satellite configuration and local solar zenith angle.

Abstract

The Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite has been making observations of the mesosphere and lower thermosphere (MLT) region for two decades. The TIMED Doppler Interferometer (TIDI) measures the neutral winds using four orthogonal telescopes. In this study, the line of sight (LOS) winds from individual telescopes are compared to the measurements from the Ionospheric Connection Explorer's (ICON's) Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument from 90-100 km altitude during 2020. With the MIGHTI vector winds projected onto the LOS direction of each TIDI telescope, coincidences of the two datasets are found. The four telescopes perform differently and the performance depends on the satellite configuration and local solar zenith angle. Measurements from the coldside telescopes, Telescope 1 (Tel1) and Telescope 2 (Tel2), are better correlated with the MIGHTI winds in general with Tel2 having higher correlation coefficients across all conditions. The performance of Tel1 is comparable to that of Tel2 during backward flight while showing systematic errors larger than the average wind speeds during forward flight. The warmside LOS winds from Telescope 3 (Tel3) and Telescope 4 (Tel4) vary widely in magnitude, especially on the nightside. Compared with MIGHTI winds, the Tel4 measurements have the weakest correlation, while the Tel3 performance is comparable to that of the coldside telescopes during the ascending phase but deteriorates during the descending phase. Based on the TIDI/MIGHTI comparisons, figures of merit are generated to quantify the quality of measurements from individual telescopes in different configurations.