Sensitivity of Total Ozone Mapping Spectrometer products to diffuse reflectance measurements

Total column ozone (O-3) amount and an aerosol index are among the geophysical properties currently retrieved from Total Ozone Mapping Spectrometer (TOMS) measurements. The accuracy with which each is retrieved depends in part on the characterization of diffuser plates used in the pre-launch instrument calibration. We present here the retrieval sensitivities to errors in the measured reflectance per steradian of these diffuser plates. In particular, errors in the wavelength dependence of the reflectance are much more important than absolute reflectance errors. We derive limits for the uncertainty of initial diffuser measurements based on reasonable goals for retrieval uncertainties: a relative standard uncertainty of 1% in total ozone and a standard uncertainty of 0.5 in aerosol optical depth. The maximum allowed la uncertainty in diffuser reflectance is 0.4% for ozone and 0.25% for optical depth, assuming that errors at different wavelengths are uncorrelated. We also examine TOMS diffuser measurements made at the Goddard Space Flight Center (GSFC) in an attempt to evaluate existing diffuser uncertainty components for O-3 and aerosol retrievals.