PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM SPACECRAFT_NAME = GALILEO_ORBITER INSTRUMENT_NAME = "NEAR INFRARED MAPPING SPECTROMETER" INSTRUMENT_ID = NIMS OBJECT = TEXT NOTE = "Introduction to the GO_1112 CD-ROM volume." PUBLICATION_DATE = 1999-10-06 END_OBJECT = TEXT END 1. Overview GO_1112 is the twelfth CD-ROM volume to contain Galileo Near Infrared Mapping Spectrometer (NIMS) Spectral Image Cubes and associated browse products. It was generated by the NIMS team in collaboration with the Planetary Data System (PDS) and the Multimission Image Processing Subsystem (MIPS) for distribution to the various Galileo project investigators, and to the community of planetary scientists. This volume is the result of systematic processing of Experiment Data Records (EDRs) derived from NIMS instrument data of Jupiter during Galileo's ninth encounter with the Jupiter system: the Callisto 9 (C9) encounter. (C9 data of Jupiter's satellites are on the previous volume in this series.) Earlier volumes covered the preceding Jupiter encounters and the cruise encounters with Venus and the Earth & Moon. Later volumes will contain cubes from subsequent encounters of Jupiter and its satellites. (NIMS EDRs are archived in a separate CD-ROM series: GO_10xx.) The Galileo NIMS instrument is an imaging spectrometer which covers the spectral range 0.7 to 5.2 micrometers, measuring both reflected sunlight and emitted thermal radiation in a region incompletely studied by the Pioneer and Voyager spacecraft. Seventeen detectors and a diffraction grating operate to produce spectra over as many as 408 wavelengths. A secondary mirror scans through 20 positions in the cross-track direction at each grating step to produce a swath of data. The scan platform on which the instrument is mounted is commanded in two dimensions to conduct extensive mapping observations over the target. A complete description of the NIMS instrument and scientific objectives is provided in the article "NEAR-INFRARED MAPPING SPECTROMETER EXPERIMENT ON GALILEO", R. W. Carlson et al., Space Science Reviews v. 60 p. 457-502, 1992. A digital preprint of this article is included on this CD-ROM in the DOCUMENT.NIMSINST directory. Additional information about NIMS may be found on the NIMS web site (http://jumpy.igpp.ucla.edu/~nims) which is also linked from the Galileo web site (http://www.jpl.nasa.gov/galileo/). WARNING: The long-term existence and location of the Galileo and NIMS web sites is uncertain. The natural form of imaging spectrometer data is the spectral image cube. It is normally in band sequential format, but has a dual nature. It is a series of "images" of the target, each in a different wavelength. It is also a set of spectra, each at a particular line and sample, over the area observed. Each spectrum describes a small portion of the area. When transformed into cubes, the data may be analyzed spatially, an image at a time, or spectrally, a spectrum at a time, or in more complex spatial-spectral fashion. Software for generating cubes from NIMS EDRs exists in the MIPS/VICAR and ISIS systems. (The MIPS and ISIS cubes are similar in structure but somewhat different in detailed content and type of processing.) The principal systematic processing products generated by MIPS for each successful observation of a target are calibrated spectral image g-cubes and/or tubes, as appropriate. In NIMS terminology, a g-cube contains data which have been resampled and projected on the target, while a tube only has unresampled and unprojected data in NIMS instrument space -- mirror position versus time. Structurally, both are cubes (see VOLINFO.TXT for details). G-cubes are generated for most observations, but they are not generated for flight calibrations, limb scans, and ride-along observations with other scan platform instruments, in which NIMS coverage is sparse. Tubes are generated for ALL observations, even when g-cubes are made; they most accurately reflect the original unresampled data. Both g-cubes and tubes are generated in two forms for the convenience of users, with data in units of radiance, and in units of I/F. Both also contain "backplanes" of geometry and other related information. Tubes additionally have backplanes of projection co-ordinates on the target, though the datasets themselves are still in instrument space. A secondary hardcopy "mask" is also produced and serves as a "browse" product. It contains a summary 3-band RGB image (if a g-cube has been made) or footprint plot (if it has not), up to six selected spectra keyed to it, various histograms and annotation. The browse products on this CD may also be found in the PDS Imaging Node web site's Planetary Image Atlas (http://www-pdsimage.jpl.nasa.gov/PDS/public/Atlas/Atlas.html). CAUTIONARY NOTE: Users of NIMS products from Galileo Jupiter operations are warned of (1) the imperfect nature of the calibration used to produce them, particularly the wavelength calibration, (2) the effect of pointing errors on their geometry and (3) the presence of radiation-induced noise in the data, and attempts to remove it in some products. [See sections 6A-C of VOLINFO.TXT for detailed discussions of these topics.] Also, an unusual instrument anomaly during part of the G1 orbit required special processing of the affected data. [See SPECPROC.TXT.] Users are encouraged to examine the readable labels and histories which begin each g-cube and tube for information on the data and its processing. UPDATES ON THE NIMS CALIBRATION WILL BE POSTED ON THE NIMS WEB SITE. NOTE ON USE OF NIMS MASKS: Users should understand that NIMS masks (browse products) are not intended as products for scientific analysis. They serve only as a guide to the spatial and spectral contents of the tube or mosaic. Browse the masks to discover which observations are of interest, then display and analyze the tubes and mosaics. (Just as a lower resolution image serves as a browse product for a higher resolution one, the NIMS mask serves as a browse product for a spectral image cube.) 2. Summary of Disk Contents This CD-ROM consists principally of radiance & I/F g-cubes of most NIMS observations, and radiance & I/F tubes -- and browse images of one or the other kind of mask -- for all observations. Ancillary files provide information about the NIMS instrument, detailed descriptions of the structure and content of the product labels, NIMS Guide(s) to the encounter(s) covered by the CD, and an index file containing selected descriptive and geometric information about each product. Directory contents are summarized below; detailed contents are available in the VOLINFO.TXT file in the DOCUMENT directory, which should be read by any prospective user of the data. Files named *INFO.TXT in most directories describe their contents in greater detail. The file you are reading (AAREADME.TXT) and ERRATA.TXT are also provided in printed form. ROOT directory -- basic introductory files: AAREADME.TXT, AAREADME.VMS, ERRATA.TXT, VOLDESC.CAT, plus WELCOME.HTM which is the base HTML file for examining the NIMS masks on this CD with a web browser. CATALOG directory -- mission, instrument and dataset descriptions which are duplicated in the PDS higher-level catalog: MISSION.CAT, INSTHOST.CAT, INST.CAT, JUPTDS.CAT, JUPMDS.CAT and REF.CAT. DOCUMENT directory -- basic documentation: VOLINFO.TXT and a brief descriptive file pointed to from the cube labels. The HTML subdirectory contains miscellaneous HTML documentation files (and a few GIF image files) subsidiary to WELCOME.HTM. The NIMSINST subdirectory contains a detailed description of the NIMS instrument, a preprint of the instrument paper. xxNIMSGD subdirectories contain detailed "NIMS Guides" to all observations in the period covered by this CD-ROM. INDEX directory -- various index tables for the data files on this CD-ROM: principally INDEX.TAB (an index of cubes) and OBSCAT.TAB (an index of observations) as well as cumulative versions of each. Each table is accompanied by a detached PDS label. CALIB directory -- Calibration data, or information about where it may be found: NIMS instrument calibration and dark value files. CALINFO.TXT presently points to a future NIMS CD-ROM which will contain the calibration and dark value files. GEOMETRY directory -- information about SPICE files, which describe spacecraft, planet, scan platform and instrument geometry and timing: GEOMINFO.TXT presently points to a future NIMS CD-ROM which will contain most of these files. Only the I-kernel and boom file are present on this CD. SOFTWARE directory -- information about how to obtain software to display NIMS cube contents: SOFTINFO.TXT. {target directories} -- a root directory for each target for which data is present on this CD-ROM: some or all of JUPITER, IO, EUROPA, GANYMEDE, CALLISTO, MISC (for ring and small satellite data), FLTCAL (for calibration, dark and star data). Each contains g-cubes and tubes of NIMS observations of that target. BROWSE directory -- contains subdirectories for each target (see above) which in turn contain JPEG versions of the masks (browse products) for observations of that target, plus associated GIF thumbnail images and ASCII labels. A target.HTM file in each links these products. See also BROWINFO.TXT in the BROWSE directory itself. 3. File Formats Most files on this disk have labels encoded in the Object Description Language (ODL) developed by PDS. An ODL label is readable by both humans and computers. It provides a formal description of the format and content of a file. For most files the ODL label appears at the beginning of the file (as is the case for this file). The cube, mask and ancillary file formats are described or referenced in the VOLINFO.TXT file in the DOCUMENT directory. Each cube file contains an attached PDS/ISIS label which describes the objects in the file. The principal object (the cube itself) conforms to the PDS and ISIS standards for the "qube" object, as defined in the PDS Standards Reference and ISIS System Design documents. Both tube and g-cube files have the extension .QUB reflecting their similar structure. Mask files come in two forms: a full JPEG image (extension .JPG) and a GIF thumbprint of the summary RGB image (extension .GIF). They are accompanied by a detached PDS label (extension .LBL). PDS label formats and documentation conform to standards as defined by the Planetary Data System Standards Reference (JPL D-7669, Part 2, November 1992, Version 3.0) and the Planetary Science Data Dictionary (JPL D-7116, November 1992, Rev. C) with the following exceptions. Labels for NIMS cube products were approved prior to the release of the Version 3.0 Standards Reference, so do not strictly conform to the Data Product Label standard in Ch. 5 of the PDS Standards Reference, Version 3.0. In particular, the Standard Formatted Data Unit (SFDU) standard from Chapter 17 of the Planetary Data System Data Preparation Workbook - Volume 2, Standards, May 3, 1991, Version 2.0 is used. 4. Software All cubes can be accessed by the ISIS (Integrated Software for Imaging Spectrometers) system, which includes software for generating, manipulating and displaying spectral image cubes. ISIS is available currently in VMS and Unix versions. More information about ISIS and how to obtain it may be found in the VOLINFO.TXT document. Simple multi-platform software for examining the cubes and masks may be included on later volumes in this series of CD-ROMs. This software is known as NASAview and is under development by PDS. Versions which access image files are available now from the PDS web site (http://pds.jpl.nasa.gov). A version which accesses cube files, and which displays spectra as well as images from them, should be available soon. 5. Disk Format This disk has been formatted so that a variety of computer systems (e.g. IBM PC, Macintosh, Sun, DEC VAX and DEC Alpha) may access the data. Specifically, the disk is formatted according to the ISO 9660 level 1 Interchange Standard, and most file attributes are specified by Extended Attribute Records (XARs). An exception is that ordinary ASCII text files (*.TXT, *.CAT, *.LBL, *.HTM) are in stream format and do *not* have XARs. For computer software that fully supports XARs, access to the CD-ROM volume will be straightforward; the disk will appear to the user to be identical to a file system of directories, sub- directories, and data files. Some computer systems that do not support XARs will ignore them; others will append the XAR to the beginning of the file. In the latter case the user must ignore the first 512 bytes of the file. For further information, refer to the ISO 9660 Standard Document: RF# ISO 9660-1988, 15 April 1988. Some older versions of the SunOS operating system cannot properly handle files with XARs, however patches are available that correct this problem. If these are not easily obtainable from Sun, contact the PDS Data Distribution Laboratory (see below) and specify the version you are running. Some older versions of the DEC VMS operating system (pre-VMS_6.0) require special software to read files *without* XARs. And more recent versions have special mount commands that allow convenient access to such files. See the file AAREADME.VMS, which is itself in VMS-standard variable-length-record format. 6. Whom to Contact for Information Information about CD-ROM Hardware and Software and general assistance in CD-ROM use: Data Distribution Laboratory MS 171-264 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 (818) 354-9343 DDL@stargate.jpl.nasa.gov Information about obtaining NIMS CD-ROMs: Helen Mortensen Multimission Image Processing Subsystem MS 168-514 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 (818) 354-0002 Helen.Mortensen@jpl.nasa.gov Information about contents and structure of NIMS CD-ROMs: Bob Mehlman UCLA/IGPP Los Angeles, CA 90095-1567 (310) 825-2434 rmehlman@igpp.ucla.edu Detailed acknowledgment of contributors to this CD-ROM may be found in Section 12 of the VOLINFO.TXT file in the DOCUMENT directory.