NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

GALILEO NIMS SPECTRAL IMAGE CUBES: JUPITER OPERATIONS (PDS)

NSSDCA ID: PSPG-00816

Availability: Data Identified but not Received

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview ================= 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, in ascending order. It is also a set of spectra, each at a particular line and sample, over the target area. 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. NIMS Spectral Image Cubes are derived from NIMS Experiment Data Records (EDRs), which contain raw data from the Galileo Orbiter's Near Infrared Mapping Spectrometer [CARLSONETAL1992]. The instrument covers the spectral range 0.7 to 5.2 micrometers, measuring both reflected sunlight and emitted thermal radiation. The cubes are of two kinds. TUBES contain data which have been converted to science units (radiance or I/F) and rearranged into band sequential form, but are unresampled and in NIMS instrument space. Tubes are made for all NIMS observations during Jupiter operations, and form a separate dataset. Data from most observations are *also* binned and resampled while being projected onto the target. These resampled products comprise this dataset. Geometric and other information is stored in backplanes of both kinds of cubes. This dataset includes radiance and I/F mosaics of most Galileo NIMS observations of Jupiter and its satellites, excluding calibrations, limb scans, ring observations, sparse ridealong observations designed for other instruments, spectrometer-mode observations and any otherwise unsuitable for projection onto the target. Observations began in June, 1996 and will continue until the (unknown) end of the mission. Spacecraft clock (SCLK) times begin at 3496645:00. The mosaics are archived in volumes beginning with GO_1104, each of which contains both tubes and mosaics from (usually) a single orbit of Jupiter, as well as browse products (masks) which provide an overview of the data. (Earlier volumes in this series contain data from Galileo flybys of Venus, the Earth and the Moon.)

Parameters ========== A band in a NIMS mosaic is generated for each of the 17 detectors at each grating step. (The detectors cover the range 0.7 to 5.2 microns.) The motion of the grating is determined by the commanded instrument mode: Mode Grating Grating Bands Samples/RIM steps increment Fixed Map/Spectrometer 1 0 17 182 Short Map/Spectrometer 6 4 102 26 Full Map/Spectrometer 12 2 204 14 Long Map/Spectrometer 24 1 408 7 A secondary mirror moves through twenty cross-track positions in the map modes, or is fixed near the center of its scan in the spectrometer modes. After the data is binned and resampled and projected, the resulting mosaic (or g-cube) has image dimensions determined by the motions of the secondary mirror, the scan platform and the spacecraft. The approximate wavelengths of the bands are determined by the mode, and by offset and start grating positions. The true wavelengths are functions of the temperature of the grating and parameters determined from the ground calibration and frequent optical flight calibrations. Known absorptions on some targets are also useful in determining these parameters. The commanded gain state is one of four sets of gains for the 14 non-thermal detectors. The three thermal detectors have two gains, automatically switching to the lower one near the mid-point of their range. Raw data values of each detector and grating step are functions of the gain state and the temperature of the focal plane assembly (FPA). Radiances are determined from raw data values using sensitivities based on the original ground calibration corrected by frequent photometric and radiometric flight calibrations. I/F values are simply radiances divided by the solar absorption at the target's distance from the sun for the wavelength in question. The NIMS grating motion capability failed prior to the I24 encounter. Subsequently, NIMS returned only 12 useful wavelengths instead of original 408. Obviously, this reduced the usefulness of the NIMS data in certain respects. However the resulting data redundancy turned out to have noise reduction advantages in the high radiation environment of Jupiter, and very useful products were generated. Further details may be found in VOLINFO.TXT in the DOCUMENT directory of the archive volume, and in the instrument paper [CARLSONETAL1992].

Processing ========== Mosaics in this dataset were generated by the Multimission Image Processing System (MIPS) at the Jet Propulsion Laboratory (JPL) from raw NIMS data on EDRs, which are available in a separate volume series (GO_10xx). For each planned observation, raw 10-bit data numbers have been re-arranged into band sequential form, converted to spectral radiance and I/F units using the best calibration available at the time of processing, and projected onto the target according to spacecraft and target position and scan platform orientation, using a complex binning and resampling procedure. Wavelength values are based on wavelength calibrations described above. Radiance values are derived from 10-bit NIMS raw data numbers by first subtracting average dark values (determined for each detector and mirror position and for each gain state), then dividing by band-dependent sensitivities, determined as described above. I/F values are derived from radiances by dividing each NIMS spectrum by the solar spectrum at the target's distance from the sun. Backplanes of geometric information are based on the position of the target and spacecraft and the orientation of its scan platform, derived from SPICE information from the Navigation Ancillary Information Facility (NAIF) at JPL. A secondary hardcopy mask (and its digital image for the volume) were also generated, based on the mosaic (if one was produced) or the tube (if not). In the former case, the mask includes an RGB summary image formed from three NIMS bands, or functions of bands, averaged spectra from one to six selected areas keyed to the image, a 2-D histogram and annotation. The masks serve as browse products for the cubes.

Data structure ============== The mosaic files follow PDS structure and labeling conventions. A PDS/ISIS label begins each file, and describes all the 'objects' within using ASCII keyword=value statements. The first object is an ISIS history object which describes the various steps of the generation process. The second object is a 2-D histogram of the cube. A third object is a 'sample spectrum qube': a 'stack' of six spectral plots, each an average over a selected area of the g-cube. (These also appear on the hardcopy and digital 'masks'.) The fourth and principal object is the actual NIMS spectral image g-cube. Spectral image cube structure follows PDS and ISIS 'qube' object standards. The 'core' of the qube is a 3-dimensional array of 32-bit VAX floating-point pixels arranged in band sequential order: sample, line and band. The pixels are in radiance or I/F units. Attached labels describe the structure and units of the cube and include vectors containing wavelengths and sensitivities of the bands. The core is followed by a set of backplanes, or 'extra' bands, with 32-bit VAX floating-point pixels. The backplanes contain a number of geometric parameters, native time, projected line and sample and 0 to 10 'spectral index' bands, each a user-specified function of the data bands. (The latter might be ratios of bands, or band depths.) The geometric backplanes are of latitude, longitude, incidence, emission and phase angles, slant distance and 'intercept altitude' (for off-limb data). (See comments in the label for details.)

Ancillary Data ============== A Postscript-format Guide to the planned observations, including footprint plots on the target, instrument parameters, etc. is included in the data set, as are tables of parameters for each observation. (Most of these parameters are also present in the cube labels. A preprint of the NIMS instrument paper [CARLSONETAL1992] is also included. Calibration files, average dark value files and SPICE files (spacecraft positions, planetary positions and constants, processed pointing geometry, spacecraft clock versus universal time, etc.) were used in generating the cubes from EDRs but are not included in this dataset. (They will be published in a separate volume at a later time.) However calibration information is present in the cube labels as vectors of sensitivity (for each wavelength) and of average dark value (for each detector). Some of the geometric information is implicitly contained in the projected 'images'; the rest is explicitly present in backplanes.

Software ======== NIMS cubes were designed to be accessed by the ISIS system, which includes extensive software for generating, manipulating, analyzing and displaying spectral image cubes. ISIS exists in VMS and Unix versions, which must be obtained independently, as described in the documentation of this data set. Other software has since been developed for displaying spectral image cubes, notably the ENVI system, written in the IDL language and available from RSI, Inc. for Unix and Windows systems. Simple multi-platform software for displaying bands, backplanes and spectra of cubes is being developed as an enhancement to the NASAVIEW image display program by PDS. NASAVIEW supports Unix, PC and Mac systems.

Media/Format ============ The NIMS mosaics and 'mask' images are archived on CD-ROM for distribution by the Planetary Data System (PDS). Formats are based on standards for such products established by PDS. Specifically, the discs are formatted according to the ISO 9660 level 1 Interchange Standard, and file attributes are specified by Extended Attribute Records (XARs).

Data Set Overview ================= 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, in ascending order. It is also a set of spectra, each at a particular line and sample, over the target area. 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. NIMS Spectral Image Cubes are derived from NIMS Experiment Data Records (EDRs), which contain raw data from the Galileo Orbiter's Near Infrared Mapping Spectrometer [CARLSONETAL1992]. The instrument covers the spectral range 0.7 to 5.2 micrometers, measuring both reflected sunlight and emitted thermal radiation. The cubes are of two kinds. TUBES contain data which have been converted to science units (radiance or I/F) and rearranged into band sequential form, but are unresampled and in NIMS instrument space. Tubes are made for all NIMS observations during Jupiter operations, and form this dataset. Data from most observations are *also* binned and resampled while being projected onto the target, forming MOSAICS (or G-CUBES) which comprise the separate MOSAIC dataset. Geometric and other information is stored in backplanes of both kinds of cubes. This dataset includes radiance and I/F tubes of all Galileo NIMS observations of Jupiter and its satellites, and associated flight calibration data. Observations began in June, 1996 and will continue until the (unknown) end of the mission. Spacecraft clock (SCLK) times begin at 3449820:00. The tubes are archived in volumes beginning with GO_1104, each of which contains both tubes and mosaics from (usually) a single orbit of Jupiter, as well as browse products (masks) which provide an overview of the data. (Earlier volumes in this series contain data from Galileo flybys of Venus, the Earth and the Moon.) Parameters ========== A band in a NIMS tube is generated for each of the 17 detectors at each grating step. (The detectors cover the range 0.7 to 5.2 microns.) The motion of the grating is determined by the commanded instrument mode: Mode Grating Grating Bands Samples/RIM steps increment Fixed Map/Spectrometer 1 0 17 182 Short Map/Spectrometer 6 4 102 26 Full Map/Spectrometer 12 2 204 14 Long Map/Spectrometer 24 1 408 7 A secondary mirror moves through twenty cross-track positions in the map modes, or is fixed near the center of its scan in the spectrometer modes. The number of lines in each image of a tube is always twenty, whether or not the mirror is moving. The number of samples is determined by the mode and the duration of the observation. (In the mosaic dataset, the image dimensions are determined by the pattern created by the motions of the secondary mirror and the scan platform.) The approximate wavelengths of the bands are determined by the mode, and by offset and start grating positions. The true wavelengths are functions of the temperature of the grating and parameters determined from the ground calibration and frequent optical flight calibrations. Known absorptions on some targets are also useful in determining these parameters. The commanded gain state is one of four sets of gains for the 14 non-thermal detectors. The three thermal detectors have two gains, automatically switching to the lower one near the mid-point of their range. Raw data values of each detector and grating step are functions of the gain state and the temperature of the focal plane assembly (FPA). Radiances are determined from raw data values using sensitivities based on the original ground calibration corrected by frequent photometric and radiometric flight calibrations. I/F values are simply radiances divided by the solar absorption at the target's distance from the sun for the wavelength in question. The NIMS grating motion capability failed prior to the I24 encounter. Subsequently, NIMS returned only 12 useful wavelengths instead of the original 408. Obviously, this reduced the usefulness of the NIMS data in certain respects. However the resulting data redundancy turned out to have noise reduction advantages in the high radiation environment of Jupiter, and very useful products were generated. Further details may be found in VOLINFO.TXT in the DOCUMENT directory of the archive volume, and in the instrument paper [CARLSONETAL1992].

Processing ========== Tube files in this dataset were generated by the Multimission Image Processing System (MIPS) at the Jet Propulsion Laboratory (JPL) from raw NIMS data on EDRs, which are available in a separate volume series (GO_10xx). For each planned observation, raw 10-bit data numbers have been re-arranged into band sequential form and converted to spectral radiance and I/F units using the best calibration available at the time of processing. Wavelength values are based on wavelength calibrations described above. Radiance values are derived from 10-bit NIMS raw data numbers by first subtracting average dark values (determined for each detector and mirror position and for each gain state), then dividing by band-dependent sensitivities, determined as described above. I/F values are derived from radiances by dividing each NIMS spectrum by the solar spectrum at the target's distance from the sun. Backplanes of geometric information and projection co-ordinates are based on the position of the target and spacecraft and the orientation of its scan platform, derived from SPICE information from the Navigation Ancillary Information Facility (NAIF) at JPL. A secondary hardcopy mask and its digital image (for the volume) were also generated, based on the mosaic (if one was produced) or the tube (if not). In the latter case, the mask includes a footprint plot of the observation on the target, averaged spectra from one to six selected areas keyed to the plot, a 2-D histogram and annotation. The masks serve as browse products for the cubes.

Data structure ============== The tube files follow PDS structure and labeling conventions. A PDS/ISIS label begins each file, and describes all the 'objects' within using ASCII keyword=value statements. The first object is an ISIS history object which describes the various steps of the generation process. The second object is a 2-D histogram of the tube. A third object is a 'sample spectrum qube': a 'stack' of six spectral plots, each an average over a selected area of the tube. (These also appear on the hardcopy and digital 'masks'.) The fourth and principal object is the actual NIMS spectral image tube. Spectral image tube structure follows PDS and ISIS 'qube' object standards. The 'core' of the qube is a 3-dimensional array of 32-bit VAX floating-point pixels arranged in band sequential order: sample, line and band. The pixels are in radiance or I/F units. Attached labels describe the structure and units of the tube and include vectors containing wavelengths and sensitivities of the bands. The core is followed by a set of backplanes, or 'extra' bands, with 32-bit VAX floating-point pixels. The backplanes contain a number of geometric parameters, native time, projected line and sample and 0 to 10 'spectral index' bands, each a user-specified function of the data bands. (The latter might be ratios of bands, or band depths.) The geometric backplanes are of latitude, longitude, incidence, emission and phase angles, slant distance and 'intercept altitude'. Projected line and sample backplanes describe the position of each pixel had the data been actually projected on the target, which, in a tube, it has not. Due to the way NIMS acquires spectra in modes with multiple grating steps, there are multiple backplanes of each of latitude, longitude and several projection co-ordinates, one backplane for each grating position (up to 24) in the instrument mode. (See comments in the tube label for details.)

Ancillary Data ============== A Postscript-format Guide to the planned observations, including footprint plots on the target, instrument parameters, etc. is included in the data set, as are tables of parameters for each observation. (Most of these parameters are also present in the tube labels.) A preprint of the NIMS instrument paper [CARLSONETAL1992] is also included. Calibration files, average dark value files and SPICE files (spacecraft positions, planetary positions and constants, processed pointing geometry, spacecraft clock versus universal time, etc.) were used in generating the tubes from EDRs but are not included in this dataset. (They will be published in a separate volume at a later time.) However calibration information is present in the tube labels as vectors of sensitivity (for each wavelength) and of average dark value (for each detector). Much of the geometric information is present as backplanes of the tube.

Software ======== NIMS tubes were designed to be accessed by the ISIS system, which includes extensive software for generating, manipulating, analyzing and displaying spectral image cubes. ISIS exists in VMS and Unix versions, which must be obtained independently, as described in the documentation of this data set. Other software has since been developed for displaying spectral image cubes, notably the ENVI system, written in the IDL language and available from RSI, Inc. for Unix and Windows systems. Simple multi-platform software for displaying bands, backplanes and spectra of cubes is being developed as an enhancement to the NASAVIEW image display program by PDS. NASAVIEW supports Unix, PC and Mac systems.

Media/Format ============ The NIMS tubes and 'mask' images are archived on CD-ROM for distribution by the Planetary Data System (PDS). Formats are based on standards for such products established by PDS. Specifically, the discs are formatted according to the ISO 9660 level 1 Interchange Standard, and file attributes are specified by Extended Attribute Records (XARs). These data are available on-line from the Planetary Data System (PDS) at: ftp://pdsimage2.wr.usgs.gov/PDS_Archive/Galileo/NIMS/go_1101/ through /go_1120/

Alternate Names

  • GALILEO NIMS SPECTRAL IMAGE TUBES: JUPITER OPERATIONS (PDS)
  • GO-E-NIMS-3-TUBE-V1.0
  • GO-E-NIMS-4-MOSAIC-V1.0
  • GO-J-NIMS-3-TUBE-V1.0
  • GO-J-NIMS-4-MOSAIC-V1.0
  • GO-L-NIMS-3-TUBE-V1.0
  • GO-L-NIMS-4-MOSAIC-V1.0

Discipline

  • Planetary Science: Geology and Geophysics

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Robert W. CarlsonData ProviderNASA Jet Propulsion Laboratoryrcarlson@issac.jpl.nasa.gov
Dr. Robert W. CarlsonGeneral ContactNASA Jet Propulsion Laboratoryrcarlson@issac.jpl.nasa.gov
[USA.gov] NASA Logo - nasa.gov