The Thermal Infrared Imaging Spectrometer(TIRIS)

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TIRIS system

The TIRIS is a demonstration system of a thermal infrared imaging spectrometer operating with uncooled optics.

Target applications include investigating the detection of plume of various compounds from air or space borne hyperspectral sensors for environmental monitoring and for CW applications.

TIRIS It is a pushbroom wedge spectrometer based on an extrinsic silicon (Si:As) 64×20 FPA, with 100 µm square pixels, hybridized to a Si ROIC. The FPA is a HYWAYS device produced by Hughes (an Aerojet PATHS FPA was used initially). As all extrinsic devices, the FPA operates at 10K.

General description:
Linear Variable Filter (LVF, or wedge filter): a custom multi-layer interference filter stack designed to match the pixel size of the FPA
Cooling: a closed cycle 2-stage Gifford MacMahon He refrigerator with 1 watt capacity at 10K
LVF mount: mechanically mounted ~300 µm over the FPA with external screws for fine position adjustment (translation and rotation)
64 Spectral bands ~0.1 µm resolution (along track direction)
20 spatial pixels (cross track direction)
Spectral range 7.5 to 14 µm
Optics: Cassagrain all-reflective uncooled telescope
Internal, cooled (10K) filter wheel with 8 positions for spectral calibration narrow band pass filters
Out of band blockage achieved with a cooled BaF filter
ZnS uncooled window
Prototype electronics:
Clocks and digital logic generated via an FPGA loaded from PROM
Biases generated via DACs
The FPA is designed such that all 20 columns are read simultaneously
Current Status
TIRIS functions in the laboratory
It is used for the study of gas plume detection
Plumes of various compounds are simulated by containing the target compound in a KBr windowed cell within the FOV of the TIRIS
For general approach to plume detection, please view the "Hyperspectrum Newsletter" and also some of the algorithms development program listed herein.

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