TIMED Doppler Interferometer: Overview and recent results

Abstract

[1] The Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite carries a limb-scanning Fabry-Perot interferometer designed to perform remotesensing measurements of upper atmosphere winds and temperatures globally. This instrument is called the TIMED Doppler Interferometer, or TIDI. This paper provides an overview of the TIDI instrument design, on-orbit performance, operational modes, data processing and inversion procedures, and a summary of wind results to date. Daytime and nighttime neutral winds in the mesosphere and lower thermosphere/ionosphere (MLTI) are measured on TIDI using four individual scanning telescopes that collect light from various upper atmosphere airglow layers on both the cold and warm sides of the highinclination TIMED spacecraft. The light is spectrally analyzed using an ultrastable plane etalon Fabry-Perot system with sufficient spectral resolution to determine the Doppler line characteristics of atomic and molecular emissions emanating from the MLTI. The light from all four telescopes and from an internal calibration field passes through the etalon and is combined on a single image plane detector using a Circle-to-Line Interferometer Optic (CLIO). The four geophysical fields provide orthogonal line-of-sight measurements to either side of the satellite's path and these are analyzed to produce altitude profiles of vector winds in the MLTI. The TIDI wind measurements presented here are from the molecular oxygen (0-0) band, covering the altitude region 85-105 km. The unique TIDI design allows for more extended local time coverage of wind structures than previous wind-measuring instruments from high-inclination satellites. The TIDI operational performance has been nominal except for two anomalies: (1) higher than expected background white light caused by a low-level light leak and (2) ice deposition on cold optical surfaces. Both anomalies are well understood and the instrumental modes and data analysis techniques have been adjusted to mitigate their effects on data quality. The analysis techniques used to derive winds are described. The TIDI wind measurements from multiple yaw cycles of TIMED have been used to extract migrating diurnal and semidiurnal tides. The migrating tide results are compared with predictions from the Global Scale Wave Model (GSWM), and results from the Upper Atmospheric Research Satellite, High Resolution Doppler Imager (HRDI) instrument. TIDI wind measurements are also compared with ground-based meteor radar observations, showing consistent results.

Simulation study for measurement of horizontal wind profiles in the polar stratosphere and mesosphere using ground-based observations of ozone and carbon monoxide lines in the 230–250 GHz region

“…Also on UARS, the limb-sounding WIND Imaging Interferometer (WINDII) observed O( 1 S) airglow emission to measure winds over 90-110 km (Gault et al, 1996b). Since 2002 the TIMED Doppler Interferometer (TIDI) has been making limb-scanning measurements of O( 1 S) and O 2 (0-0) band emissions for determining horizontal winds above 60 km (Killeen et al, 2006). Satellite measurements of mesospheric winds down to 80 km were determined from Aura Microwave Limb Sounder (MLS) observations of Doppler-shifted, Zeeman-split O 2 σ − and σ + lines around 118.75 GHz .…”

Global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide: 1. Migrating tide

“…The details of the instrument can be found in papers by Killeen et al [1999Killeen et al [ , 2006 and Skinner et al [2003]. In short, the instrument samples neutral winds on two sides of the satellite track; while one sampling track reaches the North Pole, the other flies over the South Pole.…”

“…This version (0307) of P9 line data is available online with a new zero wind implementation. More details about NCAR data are provided by Killeen et al [2006].…”

“…[4] Satellite observations from the HRDI and WINDII instruments on board the UARS satellite and the TIDI from the TIMED satellite have provided a global view of the diurnal tide [Burrage et al, 1995;Wu et al, 1995;Hays et al, 1994;Morton et al, 1993;McLandress et al, 1994McLandress et al, , 1996Lieberman and Hays, 1994;Khattatov et al, 1997a;1997b;Yudin et al, 1998;Wu et al, 2006;Killeen et al, 2006]. More significantly, satellite observations also enabled researchers to separate nonmigrating tides from migrating tides [e.g., Forbes et al, 2003aForbes et al, , 2003bOberheide et al, 2005Oberheide et al, , 2006.…”

The 5-8-Day Kelvin and Rossby Waves in the Tropics as Revealed by Ground and Satellite-Based Observations

“…TIDI views emissions from OI 557.7 nm and O 2 (0-0) to determine Doppler wind. An overview of the TIDI Doppler Interferometer can be found in Killeen et al (2006).…”