A new Fabry-Perot interferometer was built and later deployed at Resolute, Canada (75° N), the future site of the National Science Foundation Advanced Modular Incoherent Scatter Radar (AMISR). The new instrument is designed to measure mesospheric and lower thermospheric tidal waves and the upper thermosphere polar cap convection pattern using OH, O 5577 Å and 6300 Å emissions. The wind errors for these emissions are 6 m/s (3 minute integration), 1 m/s (3 minute) and 2-6 m/s (5 minute), respectively. The instrument was tested in Boulder, Colorado and measurement results are compared with nearby LIDAR mesospheric neutral wind measurements. The comparison showed good agreement between the two instruments. Neutral wind data obtained at Resolute also demonstrate that the instrument meets the design goal and is able to provide high quality data for future studies of mesospheric and lower thermospheric dynamics as well as magnetospheric-ionospheric coupling, along with ion-neutral coupling in the upper atmosphere of the polar cap. This report describes the basic design and initial results from this instrument.
Wilbert Skinner, Rick Niciejewski, Timothy Killeen, Stanley Solomon, Daniel Gablehouse, Qian Wu, David Ortland, David Gell, Alan Marshall, Edwin Wolfe, Marie Cooper, Julie Kafkalidis
The TIMED Doppler Interferometer (TIDI) is a Fabry-Perot interferometer designed to measure winds in the mesosphere and thermosphere (60-180 km) as part of the TIMED mission. TIDI is a limb viewer and observes emissions from OI 557.7 nm and rotational lines in the O2(0-0) Atmospheric band. Wind measurement accuracies approach 3 ms-1 in the mesosphere and 15 ms-1 in the thermosphere. The TIDI instrument’s performance during the first year and a half of operation is discussed in this paper. Many subsystems are working as designed. The thermal control system is holding the instrument temperatures at
their desired set-points. The CCD detector is working as expected with no changes observed in the gain, bias or read noise. The instrument suffers from a light leak that causes the background to be elevated and increases the uncertainty in the wind measurement. Nothing can be done to eliminate this problem but modeling of the background has eliminated any systematic effect. Water outgassing from the spacecraft or instrument has deposited as ice on some part of the optics and reduced the instrument’s sensitivity. This
problem has been reduced by two spacecraft rolls which pointed the TIDI radiator to view more of the earth causing the optics to warm up and sublimate much of the ice.
Timothy Killeen, Wilbert Skinner, Roberta Johnson, Charles Edmonson, Qian Wu, Rick Niciejewski, Heinz Grassl, David Gell, Peter Hansen, Jon Harvey, Julie Kafkalidis
The TIMED Doppler Interferometer (TIDI) is a Fabry-Perot interferometer designed to measure winds, temperatures, and constituents in the mesosphere and thermosphere (60 - 300 km) region of the atmosphere as part of the TIMED mission. TIDI is a limb viewer and observes emissions from OI 557.7 nm, OI 630.0 nm, OII 732.0 nm, O2(0-0), O2(0-1), Na D, OI 844.6 nm, and OH in the spectral region 550 - 900 nm. Wind measurement accuracies will approach 3 ms-1 in the mesosphere and 15 ms-1 in the thermosphere. The TIDI instrument has several novel features that allow high measurement accuracies in a modest-sized instrument. These include: an optical system that simultaneously feeds the views from four scanning telescopes which are pointed at plus or minus 45 degrees and plus or minus 135 degrees to the spacecraft velocity vector into a high-resolution interferometer, the first spaceflight application of the circle-to-line imaging optic (CLIO), and a high quantum efficiency, low noise CCD.
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