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.