NJPL1I00PDS100000000 = SFDU_LABEL RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "Introduction to this CD-ROM volume." END_OBJECT END Voyagers to the Outer Planets Volume 2 - Uranus Images 26440.04 to 26949.43 in Compressed Format This compact read-only optical disk (CD-ROM) is the second of three CD-ROM volumes containing the images returned by NASA's Voyager 2 spacecraft during its encounter with the planet Uranus. The next volume in the "Voyagers to the Outer Planets" series will complete the collection of images from Uranus. There will be additional volumes in the series containing images from the other planets visited by the twin Voyager spacecraft. This disk contains images taken during the near encounter phase, when Voyager 2 made its closest approach to Uranus in January 1986. The disk contains the best images of the rings and the satellites of Uranus. The images on this disk 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 they can be restored to their original resolution using algorithms described in documentation on this disk. Image decompression software in several programming languages is also included on the disk. 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 are 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. Each compressed full-resolution image is contained in a file and the image files are located in directories named after the principal target of the image. In alphabetical order the directories containing compressed images on 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 compressed 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 IMGINDEX.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. Please be aware that there are several problems with the first Voyager Uranus CD-ROM volume. Firstly, 76 images of Uranus were placed into the wrong subdirectory: these images all have image numbers beginning with the digits 2624 and hence they should have been placed into a subdirectory named C2624XXX under the URANUS directory; but due to a juxtaposition of digits they are instead located in the subdirectory C2264XXX. Secondly the image file C2625405.IMQ is missing from the disk. Thirdly, the image file C2449031.IMQ was truncated during processing and the image cannot be decompressed. We have updated the IMGINDEX.TAB file on this second volume to point to the actual location of the 76 misplaced files on the first volume. We have also placed the missing file and the truncated file onto this volume and updated the IMGINDEX.TAB file to reflect this. We suggest that you use the index file found on this volume in preference to the index file on the first volume.