Data Set Overview
    =================
    Raw Image Data and Label Parameters
    -----------------------------------
      Each raw image consists of an array of 8-bit picture elements or
      'pixels'. Each vidicon scan line consists of 768 pixels or 'samples'
      obtained in minor frame units of 96 pixels; 768 such scan lines
      compose the entire image. Line 1, sample 1 is at the upper left
      corner of the image; line 768, sample 768 is at the lower right
      corner of the image.  Each raw pixel value lies in the range 0 to
      255 (integers only). The units of raw pixel values are data numbers
      (DN), which are proportional (up to the telemetry system limit of
      255) to the integrated charge read out from the SEC Vidicon target
      in the camera scanning process. Since the telemetry system saturates
      at 255, the DN/charge proportionality breaks down at that level.
 
      Associated with each raw image is a set of 20 header, or label,
      records.  Each record is 360 8-bit bytes long (a concatenation of
      five 72-byte logical records). This set of 20 label records is
      generated by the Operations Control Center (OCC) software during
      image acquisition and contains various identifying parameters and
      scientific/engineering data pertinent to the image.
 
      Raw images must be corrected for the instrumental effects of the SEC
      Vidicon camera system before quantitatively meaningful data can be
      extracted from them. The methods of compensation for the radiometric
      (photometric) non-linearities and non-uniformities and the geometric
      distortion introduced by the vidicon system are described in the
      NEWSIPS Manual, Chapters 5 - 8 (Nichols-Bohlin et al., 1993
      [NICHOLS-BOHETAL1993]).  In addition, figures 2.1-15 of the same
      manual illustrate schematically the spectral formats in both
      dispersion modes, for both apertures and for all operational
      cameras.
 
    IUE Final Archive Data Products for SL9/Jupiter Events
    ------------------------------------------------------
      The output files for the Final Archive are fundamentally different
      in content, quantity, size, and format from those of the current
      reduction package (IUESIPS).  A brief description of each file is
      given below along with a definition of the associated FITS format.
      All output data from the Final Archive were translated from FITS
      format. The Table below lists the output files that are available
      only for low-dispersion data. All output data from the SL9/Jupiter
      Archive were translated from FITS format using a program developed
      at the PDS - Small Bodies Node (described in the file IUE_DOC).
 
      ---------------------------------------------------------------------
 
      *  IUE File Naming Conventions
      *  Resampled Image (SILO)
      *  Resampled Flag Image (SFLO)
      *  Extracted Low-Dispersion Spectra (MXLO)
 
      ---------------------------------------------------------------------
 
    IUE File Naming Conventions
    ---------------------------
      The file names are defined so as to allow the unique identification
      of the information stored in the file.
 
      The IUE file name is formed by the concatenation of the following
      codes:
 
      *  Camera: 3 letter code (LWP).
      *  Image number: 5 digits.
      *  File type: 2 letter code as:
        RI
          raw image
        VD
          vector displacement
        XC
          cross correlation coefficients (binary table extension of the VD
          file)
        LI
          linearized image
        LF
          flags associated with the linearized image (image extension of
          the LI file)
        SI
          resampled image
        SF
          flags associated with the resampled image (image extension of the
          SI file)
        SW
          wavelengths associated with the high-dispersion resampled image
        MX
          merged extracted spectrum (large, small or both apertures)
        WH
          whole high-dispersion extracted spectrum
 
      *  Dispersion: 2 letter code (HI, LO).
 
    Resampled Image (SILO)
    ----------------------
      The resampled image is a primary array produced by resampling the
      photometrically corrected portion of the LILO/LIHI image using the
      modified Shepard algorithm taken from the Numerical Algorithms Group
      (NAG) software package. Each pixel is resampled to the position
      determined by the summation of the vectors needed for:
 
       1. shift to photometric correction (ITF) raw space,
       2. shift from ITF space to geometrically-rectified space,
       3. rotation such that orders are horizontal,
       4. wavelength linearization,
       5. detilting of large-aperture spectra for low-dispersion extended
          sources only,
       6. alignment of the low-dispersion apertures for constant wavelength
          in the line direction,
       7. adjustment so that both LW cameras provide coverage of the same
          spectral range,
       8. adjustment to maintain the spectrum at approximately the same
          location in the file in the spatial direction (low dispersion
          only),
       9. adjustment to LWP data to put the large-aperture data at the top
          of the file,
      10. corrections for the spatial deviations (cross-dispersion wiggles)
          for the LWP and LWR low-dispersion data,
      11. heliocentric velocity correction for high dispersion,
      12. de-splaying correction for high-dispersion data, and
      13. order centroiding for high-dispersion data.
 
      The resampled image (SILO) is I*2, in scaled FN units, with the one
      coordinate in pixels and the other coordinate in angstroms (A).
      Starting wavelength and wavelength increment are stored in the FITS
      header for low dispersion. Both large- and small-aperture data are
      present in one resampled image for low-dispersion data. The FITS
      header will indicate predicted line center for large-aperture and
      for small-aperture data.
 
      The SILO image is stored as a two-dimensional primary array
      consisting of pixels, while the SIHI is also pixels. Each pixel
      represents a flux number (FN) scaled by a factor of 32 for storage
      purposes. The pixels are coded as 16 bits, two's complement
      integers, with the bits stored in decreasing order of significance.
      The associated pixel quality flags are stored as an image extension
      which has the same dimensions as the primary array. Table 11.6 in
      the NEWSIPS Manual (Nichols-Bohlin et al., 1993
      [NICHOLS-BOHETAL1993]) shows the basic FITS keywords for the main
      header and the image extension header.
 
    Resampled Flag Image (SFLO)
    ---------------------------
      This image extension is the same size as the resampled image. Like
      the linearized flag image, it contains the flag for specific error
      conditions for the corresponding pixel in the SILO/SIHI image. The
      values are stored as I*2.
 
    Extracted Low-Dispersion Spectra (MXLO)
    ---------------------------------------
      The extracted low-dispersion file uses the binary 3-D table
      extension with fixed-length floating point vectors to contain the
      extracted fluxes and associated data quality flags. Since no primary
      data are included, the extension header immediately follows the
      primary FITS header. Each row of the binary table includes the
      following columns:
 
       1. Aperture designation as 'LARGE' or 'SMALL', stored in 5 ASCII
          characters.
       2. Number of extracted points, one 16-bit integer. The number of
          extracted points is 640.
       3. Starting wavelength, one single precision floating point value.
       4. Wavelength increment, one single precision floating point value.
       5. Net flux spectrum, array with 640 single precision floating point
          values.
       6. Background flux spectrum, array with 640 single precision
          floating point values.
       7. Sigma vector, array with 640 single precision floating point
          values.
       8. Data quality flags, array of 640 16-bit integers.
       9. Absolutely calibrated net flux spectrum, array with 640 single
          precision floating point values.
 
      Wavelengths are linearly sampled, and referenced to vacuum. Double
      aperture low-dispersion spectra will contain two rows in the above
      format, with one row for each aperture. Table 11.8 in the NEWSIPS
      Manual (Nichols-Bohlin et al., 1993 [NICHOLS-BOHETAL1993]) shows the
      basic FITS keywords for the MXLO file.
 
      Note: The keyword NAXIS1 in the table extension defines the number
      of bytes per row in the table.

N/A