Thermal Infrared Imaging Spectrometer (TIRIS) Status Report Nahum Gat a , Suresh Subramanian a , Steve Ross a , Clayton LaBaw b , Jeff Bond c a Opto-Knowledge Systems Inc. (OKSI), 4030 Spencer St, Suite 108, Torrance CA 90503-2442 b Jet Propulsion Laboratory, Pasadena, CA 91109 c U.S. Army SSDC, Huntsville, AL 35807-3801 ABSTRACT The TIRIS is a pushbroom long wave infrared imaging spectrometer designed to operate in the 7.5-14.0 μm spectral region from an airborne platform, using uncooled optics. The focal plane array is a 64x20 extrinsic Si:As detector operating at 10K, provid- ing 64 spectral bands with 0.1 μm spectral resolution, and 20 spatial pixels with 3.6 milliradians spatial resolution. A custom linear variable filter mounted over the focal plane acts to suppress near field radiation from the uncooled external optics. This dual-use sensor is developed to demonstrate the detection of plumes of toxic gases and pollutants in a downlooking mode. Keywords: Imaging Spectrometer, Hyperspectral, Thermal IR, Linear Variable Filter, Uncooled Optics, Plume Tracking, Chemi- cal Detection, TIRIS. 1. INTRODUCTION The TIRIS 1 , Fig. 1, is a long wavelength infrared (LWIR, 7.5 to 14.0 μm) imaging spectrometer designed to demonstrate opera- tions using uncooled optics for dual use applications that include the detection of airborne toxic gases and pollutants, and target detection. 2-5 The concept of using uncooled optics represents an important advancement in design of long wave-length infrared (LWIR) spectral imaging systems that results in much smaller systems. The sensor uses a 64x20 focal plane array (FPA), and operates in a pushbroom mode, to generate image cubes with 20 pixels in the cross-track direction and 64 spectral bands. The spatial resolution of the system is about 3.6 milliradians while the spectral resolution is about 0.1 μm. Figure 1. TIRIS-II laboratory calibration and characterization test setup. Since the spectral signature of most organic compounds encompasses a wide range in the infrared (IR), an extrinsic silicon FPA was selected to allow operations across the entire LWIR atmospheric window. Alternative matrix arrays such as HgCdTe do not provide coverage over the entire range up to 14 μm. The downside of extrinsic silicon FPAs is that they are very expensive and they operate at 10K. The 10K operations introduces operational logistics problem: liquid helium is not readily Infrared Technology & Applications XXIII SPIE Vol. 3061, April 1997; Orlando, FL Pg. 1 Further author information: OKSI: Phone 310/371-4445; E-mail: nahum@oksi.com; URL: http://www.oksi.com C.LB.: Phone 818/354-6248; E-mail: clayton.C.labaw@jpl.nasa.gov J.B.: Phone 205/955-1670; E-mail: bondj@ssdch-usassdc.army.mil