CCSD3ZF0000100000001NJPL3IF0PDS200000001 = SFDU_LABEL
RECORD_TYPE                    = STREAM
OBJECT                         = TEXT
  NOTE                         = "Comments on Viking Orbiter image      
      CD-ROMs."
  PRODUCT_CREATION_TIME        = 1991-11-20
END_OBJECT
END


               COMMENTS ON VIKING ORBITER IMAGE CD-ROMS

1.  Purpose of This Document

    This document is a cumulative summary of comments and errors
concerning the Viking Orbiter images published so far on CD-ROMs.


2.  Comments on volume VO_1001, version 1

2.1  Format of two files in the software directory

    The files DCMPRS.MAR and MACDCOMP.HQX are stored on this CD-ROM in a
variable length record format instead of a stream file format.  This
problem is fixed on later CD-ROMs.  Copies of these two files should be
obtained from CD-ROM volumes other than volume VO_1001.


3.  Comments on volume VO_1003, version 1

3.1  Image files with wrong image data

    The top portion of two images (IMAGE_IDs 216S17 and 217S21) contain
data from the wrong image frame.  This problem exists on copies of these
images from both the EDR (Experiment Data Record) tapes and the
Planetary Archive tapes and was probably generated when the EDR images
were created.  Since most of the image data is correct in these two
images, they have been included on this CD-ROM without modification.  An
attempt will be made to recover the correct image data from the Master
Data Record tapes.  If the correct data is recovered, a new version of
these two images will be included on a later CD-ROM.


4.  Comments on volume VO_1004, version 1

4.1  PDS high-level catalog information

    The Planetary Data System high-level catalog information about the
Viking Orbiter image data sets has been revised.  The catalog
information is contained in the file CATALOG.LBL located in the LABEL
directory.  The entities that have been revised are the data set,
software, and data set processing entities.  The revisions were based on
comments from a peer review of the information.  The order of entities
in the file has also been changed.  The current order is descriptions of
the Viking Mission, the Viking Orbiter spacecraft, the Viking Orbiter
cameras, the compressed and browse image data sets, the software used to
generate the data sets, and data set processing.


5.  Comments on volume VO_1005, version 1

5.1  Image file with wrong image data

    The middle portion of image 353S01 contains data from the wrong
image frame.  This problem exists on copies of the image from both the
EDR (Experiment Data Record) tapes and the Planetary Archive tapes and
was probably generated when the EDR image was created.  Since most of
the image data is correct, it has been included on this CD-ROM without
modification.  An attempt will be made to recover the correct image data
from the Master Data Record tapes.  If the correct data is recovered, a
new version of the image will be included on a later CD-ROM.


6.  Comments on VDCOMP running on VAX/VMS systems

    The program VDCOMP.C in the SOFTWARE directory cannot be used on a
VAX/VMS system to read compressed image data directly from a CD-ROM.
The program will work if the data file is transferred to magnetic disk.
The image data can be read directly from the CD-ROM by using VAX/VMS
FORTRAN input/output routines with the DEC VFS prototype CD-ROM driver.
For more information, refer to the SOFTINFO.TXT file in the SOFTWARE
directory on this CD-ROM.