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12 October 1988 Calibration Of Satellite Shortwave Sensors Using Overcast Cloudlayer Targets
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A radiative transfer model is presented suitable for calibration of satellite instruments sensing in the solar spectrum. The model consists of two clear layers sandwiching a plane-parallel cloud layer. Clear-sky optical effects are treated with modified Beer's Law relationships and cloud optical effects are treated with the delta-Eddington method. A model inversion process is used to determine an effective cloud optical depth from surface measurements of global irradiance. The model is then used to calculate the corresponding upward irradiance at the top of the atmosphere. Upward irradiances are converted into directional radiances using empirical bidirectional reflectance factors. For sensor calibration, the model radiances are then compared to simultaneous satellite measurements of radiances from the cloud tops over the surface site. This technique has been tested by using observations of the GOES Visible and Infrared Spin Scan Radiometer. Results indicate that the VISSR-band (0.55-0.75 pm) radiance is close to nominal (slope 0.9601 compared to the expected 1.0). Significant, approximately cubic-form non-linearity of response is found (consistent with the amount of non-linearity exhibited on pre-launch calibrations). Equivalent broad-band radiance also suffers from the same type of non-linear response, with the best linear slope being about 80% of nominal, a result consistent with that anticipated for narrow-band to broad-band conversion. Observed root-mean-square errors for sensor calibration results are comparable to those found in direct comparison between uncalibrated and calibrated sensors on different satellites, indicating that the cloud-calibration approach has merit as a means of quantitative satellite sensor calibration.
© (1988) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
C G Justus "Calibration Of Satellite Shortwave Sensors Using Overcast Cloudlayer Targets", Proc. SPIE 0924, Recent Advances in Sensors, Radiometry, and Data Processing for Remote Sensing, (12 October 1988);


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