This section provides an overview of the steps involved in SCANPI. For SUPERSCANPI the same steps are applied to each individual source, just as if SCANPI were being run on each of them. Then, all of the scans are stacked together and the template fitting and flux estimation steps are repeated.

SCANPI Processing Steps

  1. First, all scans passing within approximately 1.7' of the target position are identified and extracted from the Level 1 Archive.
  2. Then the data are interpolated using cubic splines and resampled at ten samples per arcminute in all bands (the detectors were actually sampled at about 4, 4, 2, and 1 samples per arcminute at 12, 25, 60 and 100 µm). The resampling is primarily to facilitate alignment of the scans.
  3. A baseline is fit to each individual scan.
  4. The residual noise outside of the signal range (an input parameter defaulting to 2',2',2.5' and 4' at 12, 25, 60, 100 µm) is computed.
  5. A point source template is fit to each scan, and a composite template is constructed for use in fitting the coadded strings.
  6. The scans are coadded four ways:
    1. straight mean
    2. noise-weighted mean
    3. median
    4. mean with noisy detectors half-weighted

  7. These coadded scans are analyzed to:
    1. find the peak
    2. determine if a believable signal exists
    3. find the zero-crossings (baseline crossings)
    4. compute the integrated fluxes
    5. fit a point-source template
    6. determine point-source template flux
    7. compute the full width at quarter and half maximum

SCANPI Default Output

The default output consists of plots of the baseline-subtracted coadded strings with any successful template fits indicated, and a scan track plot illustrating the geometry of the included scans. (All scans are coadded as if they were parallel, with their points of closest approach to the target position aligned. Scans which are nearly opposite in direction compared to the north-most scan are reversed before coaddition.) A table of widths and flux estimators is also printed. The flux estimators include the integral between the zero crossings, the integral between fixed points, an estimate based on the peak flux and the flux from the point source template as fit.

For SUPERSCANPI this is produced for each source as well as for the combined scans of all the sources.

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