• The establishment of traceability by national measurement institutions in addition to NIST should be considered to determine if improved accuracy, reduced uncertainty in the measurement chain, and/or better documentation might be achieved, perhaps even at a lower cost.

  • The results of sensitivity studies on the parameters in data product algorithms should be summarized in a requirements document that specifies the characterization measurements for each channel in a sensor. Blanket specifications covering all channels should be avoided unless justified by the sensitivity studies.

  • Quality assessment should be an intrinsic part of operational data production. It involves providing metadata on product quality along with the data product so as to give the user an indication of deviations from expected instrument and algorithm performance and the long-term stability of the data product.

  • Validation should be undertaken for each data product or data record to provide a quantitative estimate of the accuracy of the product over the range of environmental conditions for which the product is provided. It should involve independent correlative measurement of the geophysical variable derived from the satellite data. The guidelines and protocols that are being developed for validation will lead to more standardized measurements and will make comparing the accuracy of similar products from different instruments possible. Undertaking validation both once the instrument calibration is established and following significant changes to the algorithm will contribute to establishing product continuity.

  • Wavelengths and bandwidths of channels in the solar spectral region should be selected to avoid absorption features of the atmosphere, if possible.

  • The calibration of thermal sensing instruments such as CERES and the thermal bands of MODIS should continue to be traceable to the SI unit of temperature via Planckian radiator, blackbody technology. The accumulated uncertainty of calibrations traceable to the fundamental unit of electricity via a cryogenic electrical substitution radiometer is at present much larger than that of calibrations traceable to temperature.

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