Voyagers to the Outer Planets 1: Uranus/VoyagerstotheOuterPlanetsVol1.cdr/aareadme.txt

Text File | 1988-09-15 | 5.5 KB | 105 lines

NJPL1I00PDS100000000 = SFDU_LABEL
RECORD_TYPE          = STREAM
OBJECT               = TEXT
  NOTE               = "Introduction to this CD-ROM volume."
END_OBJECT
END


                     Voyagers to the Outer Planets

                           Volume 1 - Uranus

            Images 24476.54 to 26439.58 in Compressed Format


This compact read-only optical disk (CD-ROM) is the first of three CD-ROM
volumes containing the images returned by NASA's Voyager 2 spacecraft
during its encounter with the planet Uranus. The images on this first
volume were taken during Voyager 2's approach to Uranus starting in
November 1985 and running through January 1986. They are the full
resolution (800 pixels by 800 scan lines) digital images returned by
the Voyager cameras.  No additional processing has been performed to
enhance the images. The images are compressed to permit us to pack more
data onto each volume but the images can be restored to their full
resolution using algorithms described in documentation on this disk.
Image decompression software in several programming languages is also
included on the disk.

When completed, the "Voyagers to the Outer Planets" CD-ROM set will contain
images from all the planets visited by the two Voyager spacecraft. This is
the first volume in the set. The second and third volumes will complete the
collection of Voyager Uranus images. The second volume will pick up in time
where this volume leaves off and continue up through the closest approach
to Uranus. The third volume will contain post-encounter images plus a
complete set of Uranus images in 'browse' format.  Browse images consist
of every fourth pixel of every fourth scan line, producing an image of 200
pixels by 200 scan lines.  You can use browse images to quickly locate an
image of interest to you and then go back to the compressed version of the
image to get the full 800 pixel by 800 scan line resolution.

As you may have noticed, the file that you are reading now is one of only
two files located in the main directory (the other file, VOLDESC.SFD,
contains general information similar to what you reading now but in a
format that is easier for computer programs to access). All other files
are located in directories below the main directory. The directory named
DOCUMENT contains a document file named VOLINFO.TXT that describes in
detail the organization of this disk and the format and content of the
Voyager Uranus images. It is highly recommended that you read the VOLINFO
document before trying to process image files.

The directory named INDEX contains a file IMGINDEX.TAB which is an index
to all of the Uranus images. The index table is human and machine readable.
While you can locate images by simply searching through the index yourself,
the table has been designed so that it can be easily loaded into most
database managers for fast and efficient searching.  The file named
INDXINFO.TXT in the INDEX directory describes the index table in detail.

The directory named SOFTWARE contains source and executable versions of
image decompression software written in Fortran, C and VAX Macro assembly
language.  There is one executable decompression program for IBM PCs and
another for VAX VMS systems. The file named SOFTINFO.TXT in the SOFTWARE
directory describes the software in detail.

The image files themselves are contained in directories named after the
principal target of the image.  In alphabetical order the image
directories for the Uranus volumes are:

  ARIEL            - Images of satellite Ariel
  MIRANDA        - Images of satellite Miranda
  OBERON        - Images of satellite Oberon
  TITANIA        - Images of satellite Titania
  UMBRIEL        - Images of satellite Umbriel
  URANUS        - Images of Uranus
  U_RINGS        - Images of the rings of Uranus

In addition there are two catch-all directories containing images:

  CALIB                 - Calibration images
  OTHER                 - Images that don't fit in any other category

If there are no images of a target on a particular volume then the target's
directory is omitted.  If there are more than about 100 images of a target
on a volume, the images are further divided into subdirectories based upon
their image number. Each image subdirectory has a name of the form CnnnnXXX,
where nnnn is the first four digits of the seven-digit image number.  All
images of the target with image numbers that have those first four digits
will appear in the subdirectory.

Most files on this disk have a label encoded in the Object Description
Language (ODL).  A file's ODL label is readable by both humans and
computers and it provides a formal description of the format and
content of the file.  For most files the ODL label appears at the
beginning of the file (this is the case for the file that you are
currently reading).  All image files have such an embedded ODL label
preceding the data in the file.  For files where labels can't be easily
included, a separate label file is provided that contains the ODL label
and a pointer to the file that the label describes.  These external
label files all have a .LBL file extension.  An example of an external
label is the file IMGINDX.LBL in the INDEX directory which contains
the ODL label for the index file IMGINDEX.TAB.  The LABEL directory
contains two files with external ODL labels that describe the format
and content of the engineering information that is contained within
each image file. For a description of the Object Description Language,
see the document file VOLINFO.TXT in the DOCUMENT directory.