Detector-based absolute radiometric calibration of lamps and reflectance panels

The absolute calibration of remote sensing systems is based upon radiometric standards. The irradiance standards are currently 1000-watt quartz tungsten-halogen lamps that are traced to National Institute of Standards and Technology standards by a middle party at a significant cost. Lamp instability, short lifetime and calibration inaccuracy present problems. A detector-based absolute calibration technique is described here to replace the lamp calibration in the visible portion of the spectrum (approximately 400 to 700 nm). The system utilizes a quantum efficient QED-200 trap detector in an automated facility to absolutely characterize lamp spectral irradiances or reflectance panel spectral radiances. The measured irradiance of a directly-viewed standard lamp compared favorably (within 0.8%) to the original calibration. Standard-reflectance-panel radiance measurements could not be accurately compared (within 5%) to the illuminating standard lamp irradiance because of excessive stray light in the calibration facility