NJPL1I00PDS100000000 = SFDU_LABEL RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "Introduction to this CD-ROM volume." END_OBJECT END Voyagers to the Outer Planets Volume 6 - Jupiter Selected Images in Range 13854.55 - 17574.27 in Compressed Format This compact read-only optical disk (CD-ROM) is the first of three CD-ROM volumes containing selected images taken by NASA's twin Voyager spacecraft during their encounters with the planet Jupiter. These are 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 sixth volume in the set. The seventh and eighth volumes will contain additional selected images of Jupiter. The eighth volume will also contain all of the selected Jupiter 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 a few files located in the main directory (another 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 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 the selected Jupiter 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 compressed image files are contained in directories named after the principal target of the image. In alphabetical order, the image directories for the Jupiter volumes are: AMALTHEA - Images of satellite Amalthea CALLISTO - Images of satellite Callisto EUROPA - Images of satellite Europa GANYMEDE - Images of satellite Ganymede IO - Images of satellite Io JUPITER - Images of Jupiter J_RINGS - Images of the rings of Jupiter In addition there are two catch-all directories containing images: CALIB - Calibration images OTHER - Images of stars and the sky background 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. See the document in file VOLINFO.TXT for further information about image numbers. 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.