Calibration of pyroelectric radiometers for infrared flare measurements

This report describes a set of pyroelectric radiometers which have recently been set up, successfully checked out, and are now in use for infrared flare plume radiation measurements. These radiometers meet the criteria of system linearity, fast rise time, complete commercial availability (no modification of electronics required, for example), ambient temperature operation, and reasonably flat spectral response from the visible to mid-infrared (about 15 micrometers). The instruments are presently being used (with the addition of bandpass filters) in the 3.0-4.0, 3.0-5.0 and 4.3-5.0 micrometer regions. Calibration procedures for these radiometers are described. The basis of the calibration procedure is an Electrically Calibrated Pyroelectric Radiometer (ECPR) which is traceable to the National Bureau of Standards. The ECPR is used only as a laboratory calibration device, and is a different instrument than the set of pyroelectric radiometers used for measurement of flare radiation. The ECPR is used to calibrate a blackbody. The ECPR is fitted with the band filter identical to the filters to be used with each pyroelectric radiometer. The blackbody is then used to calibrate each pyroelectric radiometer. These measurements are plotted to obtain a voltage versus irradiance calibration curve for each band being used with the pyroelectric radiometer system.