CCSD3ZF0000100000001NJPL3IF0PDS200000001 = SFDU_LABEL RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "Introduction to this CD-ROM volume." END_OBJECT END Voyagers to the Outer Planets Volume 28 - Saturn Images in Range 34476.32 - 34781.49 in Compressed Format Images in Range 34476.32 - 34781.49 in Browse Format This Compact Disk-Read Only Memory (CD-ROM) volume is one of the set of volumes containing all images taken by NASA's twin Voyager spacecraft during their encounters with the planet Saturn. The set of volumes which comprise the complete Saturn image data set begins with volume 26 of the "Voyagers to the Outer Planets" collection and proceeds chronologically through the data set. The earlier volumes in the collection contain: a complete Uranus image data set (volumes 1-3) a set of selected Saturn images (volumes 4-5) a set of selected Jupiter images (volumes 6-8) a complete Neptune image data set (volumes 9-12) a complete Jupiter image data set (volumes 13-25) The images on volumes 4-5 (selected image data) will be repeated somewhere on the complete image data set volumes. The image data will be unchanged, but corrections may have been made to descriptive information (in the label or the Index Table) such as TARGET or NOTE. In the case of corrected TARGET values, a repeated image may show up in a different directory than it did on volumes 4-5. The images 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. Sub-sampled "Browse" images consist of every fourth pixel of every fourth scan line, producing an image of 200 pixels by 200 scan lines. Browse images allow rapid location of images of interest, prior to retrieving and decompressing the compressed version of the image to get the full 800 pixel by 800 scan line resolution. Only a few files, including this one, are located in this volume's main directory. The file VOLDESC.SFD contains general information similar to what is in this file 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, as well as the format and content of the Voyager images. It is highly recommended that the VOLINFO document be read before trying to process image files. Also in the DOCUMENT directory is a file called ANOMALY.TXT which describes both missing data and known anomalies. Volumes 25 and 38 also contain a cumulative anomaly file called CUMANOM.TXT and an errata file called ERRATA.TXT. These files document the inconsistencies on volumes 13 - 25 and 26 - 38, respectively. The directory named INDEX contains a file IMGINDEX.TAB which is an index to the images on this volume. 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. Volumes 25 and 38 also contain a file, CUMINDEX.TAB, containing the complete set of images on the Jupiter and Saturn CDs respectively. The directory named SOFTWARE contains source and executable versions of image decompression software written in FORTRAN, C and VAX Macro assembly language. There are executable decompression programs for use with Macintosh, IBM PC, UNIX and VAX/VMS systems. The file named SOFTINFO.TXT in the SOFTWARE directory briefly describes the software. More detailed information is found in the .TXT files stored with the software modules in the MAC, PC, UNIX and VAX subdirectories. The compressed image files are contained in directories named after the principal target of the image. The image directories present on this Saturn volume are: SATURN - Images of Saturn S_RINGS - Images of rings of Saturn DIONE - Images of satellite Dione ENCELADU - Images of satellite Enceladus HYPERION - Images of satellite Hyperion IAPETUS - Images of satellite Iapetus MIMAS - Images of satellite Mimas RHEA - Images of satellite Rhea TETHYS - Images of satellite Tethys TITAN - Images of satellite Titan UNK_SAT - Images of unknown satellites CALIB - Unshuttered images in the DARK subdirectory OTHER - Sky background images in the SKY subdirectory Frames present in the RESTORED directory are the compressed versions of images which have been reconstructed from processed data because the raw data have been lost. Radiometrically corrected versions of the images have been reprocessed to approximate the dynamic range of the raw data. However, the background remains considerably flatter than that of raw data. These compressed reconstructed frames are named with .IRQ extensions. Their Browse counterparts are stored with the rest of the Browse data and have the standard .IBG extensions. Frames present in the FOUND directory are the compressed versions of images which should have been placed on a previous CD-ROM volume but could not be found at the time that the volume was created. These compressed frames are named with standard .IMQ extension. Their Browse counterparts are stored with the rest of the Browse data and have the standard .IBG extensions. 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 are 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 VOLINFO.TXT for further information about image numbers. The Browse image files are arranged into directories using the scheme outlined above for compressed images. The only difference is that all of the Browse image directories are located under the directory named BROWSE. Within the BROWSE directory for example, is a subdirectory named TITAN that contains all of the Browse format images of the satellite TITAN. 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. The Object Description Language is described in the document file VOLINFO.TXT in the DOCUMENT directory.