Instruments:mtm

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USU CEDAR Mesospheric Temperature Mapper (Imager)

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Acknowledgments

The Utah State University CCD Imager is operated by the Utah State University with support from the National Science Foundation.

Instrument/Model Description

The Utah State University (USU) CEDAR Mesospheric Temperature Mapper (MTM) is a mobile CCD imager that has been operated in several mid and low latitude locations since its construction was completed in 1996. The imager was built to investigate mesospheric temperature and wave induced variability using the [OH] emission (mean altitude 87 km). In March of 1996 it was tested at Bear Lake Observatory (BLO) (41.933N, 111.417W, 1981 m) and took data at BLO between 7-18 Oct 1996, 4-15 May 1997, and 4 Aug - 24 Sep, 1998. For a year between 11 June 1997 and 2 June 1998, the MTM took data alongside the Colorado State University Na Temperature lidar at Fort Collins, Colorado (40.590N, 105.140W, 1570 m). It was moved to the Starfire Optical Range (SOR) near Albuquerque, New Mexico (34.9639N, 106.4619W), and took data from October 1998 to Dec 1999 alongside the University of Illinois Wind Temperature lidar and all-sky imager and University of Western Ontario Meteor radar. The MTM was then upgraded at USU to include a capability to measure mesospheric temperature using the [O2] nightglow emission (mean altitude 94 km) as well as the [OH] emission. It was then tested and operated at BLO during the period Oct 2000-June 2001. Most recently it was deployed to Maui, Hawaii (20.75N, 156.24W) to take data from October 2001 until the present. The latter data (KINDAT=17087 for OH and KINDAT=17094 for O2) are currently available as nightly mean determinations of [OH] and [O2] rotational temperatures centered at 87 and 94 km, respectively. These data also provide relative band intensities. Higher temporal resolution data are available on request to USU. They start in 2002 to coincide with the TIMED satellite instrumentation deployment.

The USU MTM is a CCD imager that measures the hydroxyl [OH] Meinel nightglow in the (6,2) rotational band and the o2 (0,1) molecular oxygen band, both emissions occurring in the near infrared (NIR). The [OH] rotational temperature is derived from the intensity ratio of the P1(4)/P1(2) lines within the (6,2) rotational band. The rotational temperature should be close to the atmospheric temperature under normal equilibrium conditions. The [OH] emission layer is centered near 87 km (+/-2 km) with a thickness of about 8 km. The O2 emission originates at somewhat higher mean altitude of 94 km but has a similar effective layer thickness (FWHM) of about 8 km. Together these measurements permit the investigation of mesospheric temperature variability at two closely spaced but separate regions important for wave-induced (gravity wave, tides and planetary wave) as well as seasonal and longer term variations.

The MTM has a 75 deg circular field of view which corresponds to a region of about 115 km in diameter at ~90 km. The image data format are 1024 x 1024 pixels, and are binned 8 x 8 to produce a final resolution of 128 x 128 pixels. This results in a spatial resolution of 0.6 deg x 0.6 deg which corresponds to a 'superpixel' footprint of 0.9 km x 0.9 km at upper mesospheric heights. The [OH] P1(2) and P1(4) doublet lines are located at 840.0 nm and 846.5 nm respectively. The O2 emission spectrum is sampled at 866.0 nm and 868.0 nm. To monitor sky conditions and measure any background contribution a separate backgroung measurements is made at 857.0 nm. Exposures for each emission sampled are typically 60 s, with about 4 s inbetween each measurement for data storage. Measurements are made sequentially resulting in a cyclic determination of temperature for [OH] and [O2] with a periodicity of about 5-min for each emission. Occasionally, a dark image is also taken to monitor the camera diagnostics.

Measured parameters are the hydroxyl Meinel (6,2) band rotational temperature (Code 812) in tenths of Kelvin. The "error bar" in the temperature (Code -812) is the standard deviation over the night, and reflects geophysical variability. The precision for each 3 min measurement is typically 1-2 K depending on the signal level. The [O2] nightly mean temperature data (Code 812) and standard deviation (Code -812) are obtained with similar precision to the OH data. Nightly mean data include an averaging time, which can be as little as 1 hour.

For 2002 data, the relative band intensity (Code 2505) is derived from the rotational lines for OH(6,2) and O2(0,1). The standard deviation over the night is given in Code -2505. The original relative intensities have been multiplied by a factor of 0.1 so that the nighttime average relative intensities are less than 32767. Thus, the precision lost in these relative intensities is no more than 5 original units (0.5 in Code 2505).

The measurements are taken during the night during the new moon period, about 20 days per month. Cloudy periods are eliminated during the data analysis. The nominal time for measurements to start and stop are when the sun is 12 degrees below the horizon. The number of good hours (Code 61) are the number of minutes used to find the nighttime average. When the temperatures are not calculated due to fog or cloud the nighttime temperatures are set to missing to indicate data were taken. Days where data were not taken (full moon or instrumental problems) are not included in this set. Higher time resolution (one measurement every ~5 min for each emission) temperature data and relative intensity estimates for the OH(6,2) and O2(0,1) bands are available on request to USU: e-mail: mtaylor@cc.usu.edu. MTM data from previous measurements listed above are also available on request.

For the 2002 data set, when the temperatures are not calculated due to fog or cloud, the nighttime temperatures are set to missing to indicate data were taken. Days where data were not taken (full moon or instrumental problems) are not included in this set.

References for the instrument and data processing procedures

M. J. Taylor and W. R. Pendleton, CEDAR Mesospheric Temperature Mapper for Investigating Short Period Gravity Waves, The CEDAR Post, No. 29, pp 31-32, Oct 1996.
W. R. Pendleton, M. J. Taylor and L. C. Gardner, Terdiurnal oscillations in OH Meinel rotational temperatures for fall conditions at northern mid-latitude sites, Geophys. Res. Lett., 27, No.12, pp 1799-1802, 2000.
M.J. Taylor, L.C. Gardner, and W.R. Pendleton, Jr., Long-period wave signatures in mesospheric OH Meinel (6,2) band intensity and rotational temperatures at mid-latitudes, Adv. Space. Sci., 27, Nos 607, pp. 11171-1179, 2001.
M.J. Taylor, W.R. Pendleton, Jr., H.-L. Liu, C.Y. She, L.C. Gardner, R.G. Roble, and V. Vasoil, Large amplitude perturbations in mesospheric OH Meinel and 87-km Na lidar temperatures around the autumnal equinox, Geophys. Res. Let., 28, No. 9, pp. 1899-1902, 2001.
J. W. Meriwether, High latitude airglow observations of correlated short-term fluctuations in the hydroxyl Meinel 8-3 band intensity and rotational temperature, Planet. Space Sci, 43, pp 1211-1221, 1975.
D.E. Osterbrock, J.P. Fulbright, A.R. Martel, M.J. Keane, S.C. Trager, and G. Basri, Night-sky high-resolution spectral atlas of OH and O2 emission lines for echelle spectrograph wavelength calibration, Pub. Astron. Soc. Pacific, 108, 277, 1996.

Summary Plots for MTM [OH] ~87 km Nightly Temperatures over Ft Collins, Colorado

Summary Plots for MTM [OH]=x ~87 km and [O2]=+ ~94 km Nightly Temperatures over Maui, Hawaii

NOTE: Data for Jan-Jun, 2002 are being reprocessed (05/24/03). The University of Illinois lidar data at Maui are also available at http://eosl.csl.uiuc.edu/Research/Maui/.


-Revised 13 Jun 2004 by Barbara Emery