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On-the-Fly Pathology Screening

The fluxes on and off the echelle orders are used in Pass 1 to determine representative order heights and to estimate a PSF scaling factor unique to every swath of the image processed. Checks are made at this point to clip aberrant background flux values not flagged by RAW_SCREEN (e.g., from negative flux extrapolations or undetected cosmic rays). Anomalous interorder flux values in such cases are replaced with local means. The same procedure is repeated if necessary to substitute highly anomalous interorder fluxes with the means of the four neighboring interorder fluxes. This procedure was adopted to cope with small pixel clusters in the long-wavelength cameras that are prone to excessive negative extrapolations.

Last updated: 29 July 1997