The data set described in this document is the best set of measurements possible with the personnel, equipment, methods, and calibration procedures available to us. We found that making continuous measurements with complex, sensitive equipment, and accounting for all sources of error in order to specify total measurement uncertainty were not trivial tasks. Total uncertainty is a combination of an estimated total spectral bias error and total spectral random error. The standard deviation of these measurements, multiplied by three, was converted to a percentage of the mean. Figure 5-3 shows the results obtained for one of these comparisons using the integrating spheres.
Similar results occur with the other configurations.
Temperature control of the spectroradiometers with silicon detectors was important. This resulted in amplifier millivolt drift errors and noise in some of the spectra. We achieved better temperature control by shielding the spectroradiometers with Mylar sheets supported by foam offsets to allow air flow. Measurement uncertainty for the broadband and meteorological data is based on the calibration histories provided by the measurement sites and characteristics of the instruments. Instruments used at FSEC were calibrated by FSEC, and nominal values for random and bias errors for these types of radiometers were used in the uncertainty analysis.