10.2.5 EXTRACT Output

The main output data product produced during EXTRACT is the high-dispersion MX FITS file (MXHI). The MXHI contains the net (background-subtracted) integrated flux spectrum, the Chebyshev-characterized background spectrum scaled up to the extraction slit area, the $\nu$ flag spectrum, the ripple-corrected spectrum, the absolutely-calibrated and ripple-corrected net flux spectrum, and the noise spectrum stored in a FITS binary table extension. The net flux, background, ripple, and noise spectra are in units of FN, the flag spectrum is in bit-encoded unitless values, and the calibrated flux spectrum is in physical units of ergs sec^-1 cm^-2 Å^-1. See Chapter 11 for details concerning the process of absolute flux calibration and ripple correction.

The background values for locations before the short-wavelength ends or past the long-wavelength ends of the orders are replications of the first (or last) valid background value. The net flux and noise spectra are computed over the entire wavelength space of the high-dispersion SI, but locations that are outside the camera target area will have net fluxes equal to zero because these regions do not contain any valid image data. The absolute calibrations are valid over wavelength limits of 1150-1980Å for SWP and 1850-3350Å for LWP and LWR. Beyond these limits the calibrated net fluxes are set to a value of 0 and and have a $\nu$ flag value of -2. The valid wavelength limits of the calibrated spectra are consequently somewhat truncated as compared to the net flux spectrum.

The EXTRACT module writes the following information to the HISTORY portion of the image label:

• noise model version number,
• aperture-dependent extraction/calibration information:
  • slit height information,
  • found line position for a representative ``checkpoint'' echelle order (i.e., order 100 for the SWP or order 90 for the LWP and LWR). The LWP processing HISTORY initially reported the line position for order 100. This was subsequently changed to order 90 after the start of the processing effort, as this order is a region of higher sensitivity than order 100 for the LWP and LWR. This change only affects LWP and LWR images processed after July 28, 1997.
  • order centroiding warnings (if applicable),
  • ripple calibration version number,
  • absolute flux calibration derivation information,
  • absolute flux calibration version number,
  • absolute calibration mode (i.e., point or trailed),
  • absolute calibration epoch,
  • camera rise time,
  • effective exposure time,
  • THDA of image,
  • reference THDA,
  • temperature-dependent sensitivity correction coefficient,
  • temperature correction factor,
  • time-dependent sensitivity degradation correction version number,
  • time-dependent sensitivity degradation correction mode,
  • sensitivity degradation calibration epoch, and
  • observation date.