MISR: In-Flight Radiometric Calibration and Characterization Plan

laboratory measurements. In order to account for surface inhomogeneities over the MISR field-ofview,measurements need to be made over a 3x3 pixel area.As this technique is the easiest to implement, it will be the first operational VC techniqueutilized by the MISR team. Although the uncertainty in the reflective-based VC are welldocumented for the nadir-view case 10 , an analysis for MISR’s off-nadir view angles will benecessary. Table 5.4 details the error budget for MISR calibration, using the reflectance-basedcalibration methodology.Table 5.4. Surface reflectance-based uncertainties, ρ eq =1.0SourceReflectance knowledge of field reflectancestandardUncertainty (%)for the D cameraUncertainty (%) forthe A cameraBudget Actual Budget Actual1.0 1.0Field radiometer stability 0.5 0.5Differences in radiometer/ MISR spectralprofileScene spatial sampling (averaging toMISR field-of-view1.0 1.01.0 1.0Scene relative spectral knowledge 1.0 0.5Scene relative BRF knowledge 1.0 1.0Atmospheric correction 4.0 2.0Spectral integration of TOA radiances toMISR band-averaged value0.5 0.5Total Uncertainty (Root Sum of Squares) 4.6 3.05.3 HISTOGRAM EQUALIZATIONThe absolute calibration of a pixel can be considered the product of the at-launch arrayresponse, array degradation, and relative pixel response. The first two of these is reported at themost responsive pixel of the array, and the third parameter is normalized to this pixel. There are1504 relative calibration coefficients per band. The relative response refines the measure of thearray response to account for local deviations in response, as occur due to filter and detector smallscale imperfections, field angle variations, and broad scale transmittance variations of the filter.The latter effect is particularly large for those few filters which were cut along radial lines, ascompared to the filter deposition center. Without a relative calibration adjustment, artificial north/south stripes would appear in the MISR images. Although the OBC can be used to provide bothIn-flight Radiometric Calibration and Characterization Plan, JPL D-1331549