Data Set Overview
      =================

      This data set contains products acquired by the Mastcam 
      instruments.  There are two cameras in this set with 34 
      and 100 mm focal lengths referred to as MAST_LEFT and 
      MAST_RIGHT, respectively.

      This data set uses the Committee on Data Management and
      Computation (CODMAC) data level numbering system. The MSL
      Mastcam RDRs are considered Level 4 or Resampled.  The RDRs
      are created from EDR images and contain irreversibly
      transformed data due to the nature of JPEG decompression.


      Processing
      ==========

      After extracting and decompressing (if needed) EDR products,
      2 RDR products are created for each EDR.  These are
      generated from validated data. The products are:

      (1) decompressed and radiometrically calibrated (16-bit),
      (2) decompressed, radiometrically calibrated, and color corrected
          (8-bit).


      Data 
      ====

      The RDRs produced have detached PDS-compliant labels.
      The Mast Camera (Mastcam), Mars Hand Lens Imager (MAHLI),
      and Mars Descent Imager (MARDI) Experiment Data Record (EDR)
      and Reduced Data Record (RDR) PDS Data Products Software
      Interface Specification contains a detailed description of
      the RDR formatted products.

      There are 2 zstack data types (1 image, 1 thumbnail) that can
      be wrapped into the original data format that is transferred
      from the cameras. Some of these are compressed in a format
      which can reproduce an image identical to the original image
      on the instrument (lossless compression), some are transferred
      in lossy format, some are full-scale and others sub-sampled
      (the only sub-sampled is by a factor of 8, used to produce
      thumbnail images). The RDR data file includes the camera
      mini-header generated by the camera, followed by original
      image data as formatted by the camera.

      Not including sub-framing, Mastcam can take a variety of image 
      data formats and accomplish this by internal processing. The 
      cameras always acquire raw 12-bit data. Normally, the 12-bit 
      raw data are converted from 12-to-8-bits through the use 
      of a variety of companding (compress/expand) lookup tables, 
      the most generally used being a modified square-root encoding 
      scheme that allocates additional values to low DNs. These 
      companded 8-bit images can then be processed either immediately,
      and stored into each camera's 8-Gbyte buffer, or they can be 
      stored unprocessed in the buffer, and then later processed in 
      response to downlink commands.  It is this flexibility that 
      leads to the complexities of the raw data format and its 
      description.

      Focus merge images are always JPEG 444 color images based on
      the 2 to 8 source images.

      In addition to the 12-to-8-bit companding, on-board processing
      includes the following capabilities: Bayer pattern interpolation,
      lossless compression, and JPEG compression. Except for
      thumbnails, the cameras do not support sub-sampling or
      resampling, but do support sub-framing.

      Thumbnails are produced by creating a scratch JPEG image, and
      extracting the lowest order coefficients of the discrete cosine
      transform 8x8 pixel compression block, or minimum compression
      unit (MCU), which is essentially the average of the 8x8 spatial
      domain MCU. These coefficients are then assembled into a smaller
      image which is then JPEG compressed.  The extraction of these
      coefficients is the only way Mastcam images are ever sub-sampled.

      The following is a table of the different zstack product types
      generated by Mastcam which are contained within the raw camera
      data record.
 
      Type  Product                 Format     Pixel bits
      -----------------------------------------------------
      R     Focus Merge Image       JPEG 444   48
      T     Focus Merge Thumbnail   JPEG 444   48


      Refer to the Mast Camera (Mastcam), Mars Hand Lens Imager (MAHLI),
      and Mars Descent Imager (MARDI) Experiment Data Record (EDR)
      and Reduced Data Record (RDR) PDS Data Products Software
      Interface Specification for further details on the Mastcam data
      products and RDR processing.

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