<title>Long Wave Infrared Testing At NBS</title>

Abstract

At present, National Bureau of Standards (NBS) work in the Long Wave Infrared (LWIR) spectral region is performed using three calibration facilities. These facilities are: 1) a spectral calibration facility for "medium temperature" (350-1300 K) blackbodies, 2) a broadband facility for calibrating blackbodies (-50 - +150°C) against a room temperature background and 3) a facility for calibrating blackbodies (150-600 K) in a cryogenic environment. Two recent calibrations for the LWIR community will be described to illustrate the features and limitations of the present NBS facilities: for the first calibration [in facility (3)] the total radiant output at a source in a small, well-defined solid angle was measured using an electrically calibrated absolute radiometer; for the second [in facility (2)], a source was radiometrically compared with a high-quality, variable temperature blackbody using an IR radiometer with a variable wavelength filter. Future plans to enlarge and upgrade the cryogenic facility to provide increased sensitivity will be described. Systematic studies of the errors due to diffraction, polarization, and attenuation are planned. Future work to explore the possibility of basing calibrations on self-calibration techniques with LWIR detectors will also be described.