Calibration and characterization of trap detector filter radiometers

We describe the development of a mechanically simple, radiometrically stable transfer radiometer designed for both radiance and irradiance measurements. The filter radiometer consists of a six-element Si trap detector, a temperature stabilized filter wheel with up to 5 filters, and two precision apertures in a Gershun tube arrangement. With the Gershun tube installed, the instrument operates in radiance mode; with the front aperture removed, in irradiance mode. Two trap detector filter radiometers have been designed and built by the National Institute of Standards and Technology (NIST) for use in remote sensing applications. The filter radiometers have been characterized for optical and electrical performance, and have been calibrated for responsivity using both narrow-band, tunable-laser-illuminated and broad-band, lamp-illuminated integrating sphere sources. This paper describes the filter radiometer design, characterization, and deployments for two remote sensing projects.