In 1996, the National Institute of Standards and Technology (NIST), with the support of the National Atmospheric and Oceanic Administration (NOAA), designed and built two single channel, dual mode radiometers. The radiometers are used to assess the accuracy and monitor the stability of the standards of spectral irradiance and radiance used to calibrate the various optical sensors in the Marine Optical Buoy (MOBY) Project. Each radiometer consists of two interchangeable input optical systems and a detector assembly. One input optical system is for the irradiance mode, and the other is for the radiance mode. The detector assembly in each radiometer consists of an interference filter, silicon photodiode, and a preamplifier with variable gain. The specifications of the interference filters were determined by consideration of planned ocean color satellite sensors and published protocols. For the first radiometer, the center wavelength and full width half maximum (specified to be 412nm and 12nm, respectively) was chosen so that the sources could be studied in the blue spectral region, where the radiant flux is more sensitive to systematic effects. For the second radiometer, the filter specifications were 875nm and 10nm. This provides an assessment of the change in the relative spectral shape of the source in addition to the assessment of the radiometric accuracy. The blue and short wave infrared channels of the dual mode radiometers complement the typical choice of commercial vendors to provide source monitoring near 550nm.
Proceedings Title: Poster Presentation: Oceans from Space
Conference Dates: October 9-13, 2000
Conference Location: Venice, IT
Conference Title: NASA Web Site
Pub Type: Conferences
MOBY, ocean color, radiometric calibration, spectroradiometry, transfer radiometers, VXR