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Session 85 - Instruments, Databases and Techniques.
Oral session, Thursday, June 13
We present a brief overview of the design and construction of a Two Grating Infrared Spectrometer (TGIRS), a new mid-IR array, dual grating spectrometer for the 7.0-13.8 \mum region built at the University of Denver (DU). This instrument has been designed to monitor silicate features in evolved stars, but is flexible enough to accomodate a variety of astrophysical investigations. The instrument uses diamond-turned aluminum optics to allow warm optical alignment and eliminate differential contraction of the optics while operating at 6.5 K. Two gratings are used in the optical design to provide a resolution of about 800. The first grating cross disperses the flux into several orders, 8-14. The second grating is the high resolution grating which disperses the flux into each of the above orders over the wavelength range of the instrument. This second grating has two position settings controlled by a swing arm device to allow for both maximum spectral coverage and efficient use of the array detector with the least amount of moving hardware. The entire assembly is cooled with a Gifford-McMahon refrigerator so that it may later be adapted for use during remote observing. The array is a Rockwell 128X128 Si:As BIB Hybrid Focal Plane Array sensitive to 26 \mum. The dewar is being custom built by J. K. Henricksen and Assoc. in Vista, CA. Short wavelength IR and optical radiation is blocked with a long pass filter. The slit of the instrument is 1"X 4" allowing for both spectral and spatial coverage of the objects being studied. The electronics package and software for readout were developed by Wallace Instruments and are already in use on our TNTCAM at DU. With "first light" scheduled for summer '96, we expect to have photographs of the instrument for display and data by year's end. We acknowledge partial support under NASA grant NGT-51290.
Program listing for Thursday