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 gaspra_nims_hires_radiance volume." PUBLICATION_DATE = 2012-07-23 END_OBJECT = TEXT END 1. Overview The gaspra_nims_hires_radiance data volume contains a radiometrically calibrated and spatially rectified Galileo Near Infrared Mapping Spectrometer (NIMS) spectral image cube and ancillary data files of the highest spatially observations of asteroid 951 Gaspra by that sensor. It was generated by Science Application International Corporation for the contract NNH10DC54C for the NASA Planetary Mission Data Analysis Program. 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 copy of this article is included on this data volume's DOCUMENT directory. 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. The gaspra_nims_hires_radiance data product contains a spectral image cube in a Flexible Image Transport System (FITS) file that enables it to be read by multiple astronomical software tools. The file contains a spectral image cube array of floating point (little endian) radiance values that can be converted into units of reflectance or emission. 2. Summary of the Data Volume Contents This data volume consists principally of radiance spectral image cube of the highest spatial resolution observation of asteroid 951 Gaspra by the Galileo NIMS sensor. Ancillary files provide calibration data, information about the NIMS instrument, the NIMS guide to the asteroid 951 Gaspra encounter, data file descriptions, software information, and an index file containing selected descriptive and geometric information about the data products contained in the data volume. 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, ERRATA.TXT, and VOLDESC.CAT. CATALOG directory -- mission, instrument and dataset descriptions which are duplicated in the PDS higher-level catalog: GALILEOMISSION.CAT, GOHOST.CAT, GONIMSINST.CAT, GASPRADS.CAT, PERSON.CAT, REF.CAT, and GASPRA.CAT. DOCUMENT directory -- basic documentation: VOLINFO.TXT, DOCINFO.TXT, GDINFO.TXT, NIMSINST.TXT provide an overview of the data volume, document file descriptions, 951 Gaspra asteroid observation descriptions, and NIMS instrument descriptions respectively. Detailed asteroid 951 Gaspra observation information is contained in the files nimsgd1.ps, nimsgd2.ps, nimsgd3.ps, nimsgd4.ps, nimsgd5.ps, nimsgd6.ps, nimsgda.ps, and nimsgd.lbl. Detailed NIMS instrument information is stored in the files instpub.asc, instpub.lbl, instfg01.ps, instfg02.ps, instfg03.ps, instfg04.ps, instfg05.ps, instfg06.ps, instfg07.ps, instfg08.ps, instfg09.ps, instfg10.ps, instfg11.ps, instfg12.ps, instfg13.ps, and instfg14.ps. INDEX directory -- an index table for the data files in this data volume - INDEX.TAB (an index of spectral image cube files). This table is accompanied by a detached PDS label file. CALIB directory -- a spectral image cube that contains the calibration and dark values employed to calibrate the gaspra_nims_hires_radiance data product. CALINFO.TXT is a pds label that describes the spectral image file and how it was used to produce the gaspra_nims_hires_radiance data product. EXTRAS directory -- contains TIFF image files of band 1 and two spectra plots from the gaspra_nims_hires_radiance data product. 3. File Formats The primary data file of the graspra_nims_hires_radiance data volume is packaged in the Flexible Image Transport System (FITS) file format as defined by the FITS Support Office at NASA Goddard Space Flight Center (http://fits.gsfc.nasa.gov). This file has a .FITS suffix. Many of the support files on this disk have labels encoded in the Object Description Language (ODL) developed by PDS. An ODL label is readable by both human 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). A calibration image spectral cube file contains an attached PDS/ISIS label which describes the objects in the file. The principal object (the spectral image 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. This file has a .QUB suffix. Other supporting files are formatted as ASCII, postscript, and as TIFF files. The American Standard Code for Information Interchange (ASCII) is the standard text file format as established in ISO/IEC 8859-1 by the International Standardization Organization (ISO) and the International Electricaltechnical Commission (IEC). Postscript is a file format that is defined by Adobe Systems for use in printing documents. The Tagged Image File Format (TIFF)is a standard image file format also defined by Adobe Systems. PDS label formats and documentation conform to standards as defined by the Planetary Data System Standards Reference (JPL D-7669, Part 2, February 27, 2009, Version 3.8) and the Planetary Science Data Dictionary (version 1r82, February, 2011). 4. Software The primary data product of the gaspra_nims_hires_radiance data volume can be read with astronomical image software packages that can ingest the FITS file format. This includes IDL, a product of ITTVIS (http://www.ittvis.com) with the IDL Astronomy User's Library at NASA Goddard Space Flight Center at http://idlastro.gsfc.nasa.gov . ISIS (Integrated Software for Imagers and Spectrometers) 3.0 may also be used to ingest the FITS file for analysis and is available from the USGS via http://isis.astrogeology.usgs.gov/ . 5. Whom to Contact for Information Information about contents and structure of the gaspra_nims_hires_radiance data volume: James Granahan SAIC 10932 Blake Lane Bealeton, VA 22712 (703) 400-1573 james.c.granahan@saic.com Detailed acknowledgment of contributors to this data volume may be found in Section 12 of the VOLINFO.TXT file in the DOCUMENT directory.