DU's TEN AND TWENTY MICRON ARRAY CAMERA (TNTCAM)

Denver University, Department of Physics and Astronomy

Denver, Colorado 80208 USA

News about TNTCAM Mark 2

9/96 Info pertinent to TNTCAM data (LaTex formatted)

TNTCAM is Denver University's Ten aNd Twenty micron mid-IR array CAMera. TNTCAM utilizes a Rockwell HF-16 Si:As focal plane array, 128 x 128 in size, with 75$\mu$m pixels and 16 channel outputs, and efficiently detects wavelenghts from shortward of 4 microns to longward of 26 microns, with a quantum efficiency ranging between 5 and 50\% (Klebe et al. 1996). The camera incorporates a compact optical design, wherein the entrance aperture is placed at the rotation axis of the filter wheel, which minimizes off-axis angles from the spherical collimating and re-imaging mirrors. This optical configuration produces diffraction limited images at the Mt. Jelm (WIRO) 92 inch and the Mt.Lemmon (MLOF) 60 inch telescopes. The filters are located at the Lyot stop, thereby minimizing the effects of inhomogeneities within the filters on photometric results. The collimating and re-imaging mirrors are housed in separate compartments, thereby shielding the array from unwanted stray radiation. TNTCAM has demonstrated background noise limited performance (not due to electronics) at both WIRO and MLOF. The array, optics and filter wheel are housed in a LN2/LHe dewar provided by the University of Minnesota IR Astronomy group, and has an operational hold time of 18 hours. \\

Reference: Klebe, D., Dahm, M. and Stencel, R. 1996 in Polarimetry of the Interstellar Medium, eds. W.Roberge and D.Whittet, Astron. Soc. Pacific Conf. Series Vol. 97, pp. 79-84. \\

We are currently using the following filter set (installed 8/96):\\ 4.8 microns +/- 0.3 OCLI std. "M" band filter 7.8 um +/- 0.39, "methane band" filter (Jupiter observations);\\ 10.3 um +/- 0.18, OCLI std. silicate band;\\ 11.6 um +/- 0.58, OCLI std. silicate band;\\ 12.0 um +/- 0.20, special silicate band (in-house item);\\ 17.9 um +/- 0.21, Q1 (Klebe et al. 1994 BAAS 26:896;)\\ 20.8 um +/- 0.76, Q3 ( " );\\ 24.5 um +/- 0.32, Q5 ( " ),\\ Previous runs have used an infrared-opaque disk to provide a dark current measurement, but the stability has allowed us to remove this for an active filter in the 8 element filter wheel.\\

This selection of filters provides the opportunity to monitor changes in silicate emission feature(s) plus the shape of the dust continuum. Note that the 7.8 micron filter overlaps the 8 micron PAH line. If it is concluded that alternative filters would be preferable for the particular case of the proposed observations, these can be readily swapped into place. For instance, to better establish the IR continuum, a "K" band (2.2 microns) might replace the Q3 band (which is affected by water). \\

There is a long tradition of infrared atmospheric spectroscopy at Denver University (DU) and this provides an infrastructure upon which we have been building. For example, we have access to a substantial inventory of of special infrared filters and optical components that assure equipment redundancy and field success.\\

TNTCAM has a proven track record, with the following observing record:\\ First light, WIRO, 5/14/95;\\ WIRO, Nov.1995, 4 nights, 400Mb data;\\ WIRO, Jan.1996, 5 nights, 500Mb data;\\ WIRO, Mar.1996, 4 nights, 500Mb data;\\ Mt.Lemmon 60in, Apr.1996, 6 nights, 750Mb data;\\ IRTF, May/June 1996, 3 partial nights, 400 Mb data; WIRO, Jun.1996, 5 nights, 500 Mb data, \\ where a typical nod pair requires 0.14Mb per FITS file. \\

Noteworthy observations to date have included:\\ Jupiter, monitoring in support of the NASA/JPL Galileo probe and related Io events at WIRO and IRTF (G.Orton, R.Howell);\\ Long period variables (PhD thesis data for M.Creech-Eakman, DU);\\ Trapezium region imaging (Masters' thesis data for M. Dahm, DU);\\ Vega disk star observations (in support of ISO observations, RStencel);\\ Star-froming regions and star-burst galaxies (DKlebe);\\ Comet Hyakutake (4/13/96 at MLOF, in collaboration with Minnesota);\\ Comet Hale-Bopp (5/31/96 at IRTF, in collaboration with Minnesota).\\ Although we've been saying : 'Have camera, will travel' since we have become experienced with successfully using TNTCAM at a variety of observing facilities, the installation later this year of DU's new twin 0.7 meter telescopes at our nearby extreme high altitude Mt.Evans observatory (14,125 ft elev) will add to the telescope time possible for TNTCAM, although we will opt to use the largest apertures available for the proposed observations. \\

Additionally, we imaged the Trapezium, comet Hyakutake and Jupiter, obtained with TNTCAM during 1996 at WIRO, MLOF and IRTF. These were reduced and analyzed using IRAF and IDL on our Sun workstation at DU.\\

For reference, the DU-TNTCAM image specs are as follows:\\ \begin{tabular}{lrrrr} \hline Telescope: & MBT & Lemmon & WIRO & IRTF\\ \hline \hline Aper (m) & 0.72 & 1.52 & 2.33 & 3.00\\ CAM int f/number & 15 & 15 & 15 & 15\\ f.l.(m) & 10.8 & 22.8 & 35.0 & 45.0 \\ \hline Tel.Resolution (arcsec) & & & &\\ 0.5 $\mu$m & 0.17 & 0.08 & 0.05 & 0.04\\ 5 $\mu$m & 1.74 & 0.83 & 0.54 & 0.42\\ 10 $\mu$m & 3.48 & 1.65 & 1.08 & 0.85\\ 20 $\mu$m & 6.95 & 3.30 & 2.15 & 1.69\\ \hline Cam.Resolution (arcsec) & & & &\\ Per 75 $\mu$m pixel & 1.42 & 0.68 & 0.44 & 0.35\\ Total fov = 128 pixels & 182.36 & 86.62 & 56.49 & 44.42\\ AU/pxl at 10 pc & 14 & 7 & 4 & 3 \\ \hline \hline \end{tabular} \\ \\

TNTCAM will be used at our new Mt. Evans Meyer-Binocular telescope, which is being installed at DU's Mt.Evans Observatory located at 14,125 ft above sea level. We are seeking partners interested in developing a 4 meter optical-IR telescope for the site as well (email rstencel@du.edu). }

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