/*============================================================================*/ /* Streamlined Data Set Template (combined EB and SC data sets) */ /*============================================================================*/ /* Template: Data Set Template Rev: 1993-09-24 */ /* Note: Complete one for each data set. Identify multiple targets */ /* associated with the data set by repeating the 3 lines for the */ /* DATA_SET_TARGET object. Identify multiple hosts associated */ /* with the data set by repeating the 4 lines for the */ /* DATA_SET_HOST object. Identify multiple references associated */ /* with the data set by repeating the 3 lines of the */ /* DATA_SET_REFERENCE_INFORMATION object. */ /* Hierarchy: DATA_SET */ /* DATA_SET_INFORMATION */ /* DATA_SET_TARGET */ /* DATA_SET_HOST */ /* DATA_SET_REFERENCE_INFORMATION */ OBJECT = DATA_SET DATA_SET_ID = "GO-V-NIMS-4-MOSAIC-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "NIMS Spectral Image Cubes of Venus" DATA_SET_COLLECTION_MEMBER_FLG = "Y" START_TIME = 1990-041T01:49:59 STOP_TIME = 1990-048T05:59:02 DATA_SET_RELEASE_DATE = 1996-02-15 DATA_OBJECT_TYPE = QUBE PRODUCER_FULL_NAME = "Dr. Robert W. Carlson" DETAILED_CATALOG_FLAG = "N" DATA_SET_DESC = " 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 target. 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 Cube files are derived from NIMS Experiment Data Records (EDRs), which contain raw data from the Galileo Orbiter Near Infrared Mapping Spectrometer (CARLSONETAL1992). The raw EDR data have been re-arranged into band sequential form, converted to spectral radiance units based on ground and flight calibration of the NIMS instrument, and (in most cases) projected onto the target based on the position of the spacecraft and target and the orientation of the spacecraft's scan platform. This dataset contains files of projected data ('mosaics') only. Another dataset contains files of unprojected data ('tubes'). Calibration and geometric information used are the best available at the time of publication of these files, but they are subject to continual improvements as data analysis proceeds. Thus better cubes may be generated in the future. Parameters A band in a NIMS cube is generated for each of the 17 detectors at each grating step. The motion of the grating is determined by the commanded instrument mode: Mode Grating Grating Bands steps increment Fixed Map/Spectrometer 1 0 17 Bandedge Map/Spectrometer 2 variable 34 Short Map/Spectrometer 6 4 102 Full Map/Spectrometer 12 2 204 Long Map/Spectrometer 24 1 408 The wavelengths of the bands are determined by the commanded start and offset grating positions, and by wavelength calibrations conducted on the ground and occasionally during flight. They are also weak functions of grating temperature. The pixels in a cube of a targeted observation are in (scaled) units of radiance, derived from the 10-bit raw data numbers by applying band-dependent sensitivities, which are in turn products of ground and flight calibrations, of the commanded gain state and chopper mode and of the focal-plane-assembly (FPA) temperature. The radiance scaling is band-dependent, and is specified by vectors of offset and multiplier values. Processing Cube 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 CD-ROM series (GO_10xx). For each planned observation, raw 10-bit data numbers have been re-arranged into band sequential form, converted to spectral radiance units according to ground and flight calibration of the NIMS instrument, and projected onto the target according to spacecraft and target position and scan platform orientation, using a complex binning procedure. A secondary 'browse' product of this procedure is a hardcopy 'mask', a digital image of which accompanies the cube. Data structure The cube 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 [8] 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 cube. (These also appear on the hardcopy and digital 'masks'.) The fourth and principal object is the actual NIMS spectral image cube. Spectral image cube structure follows PDS and ISIS 'qube' object standards. The 'core' of the qube is a 3-dimensional array of 16-bit signed integers, arranged in band sequential order: sample, line and band. (ISIS also supports 8-bit unsigned integers and 32-bit real values.) The core of NIMS cubes in this dataset contains scaled 16-bit radiance values, the result of applying the NIMS calibration to 10-bit raw data numbers. The scaling parameters (offset and multiplier) for each band are stored in the label, as are the wavelengths and other band-dependent quantities. The core is followed by a set of backplanes, or 'extra' bands, made up of 32-bit VAX floating point pixels. The backplanes contain seven geometric parameters, the standard deviation of one of them, the standard deviation of a selected data band, 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 latitude, longitude, incidence, emission and phase angle, slant distance and 'intercept altitude'. (See NOTEs in the cube 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 late version of the NIMS instrument paper (CARLSONETAL1992) is also included. Calibration files, spike 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. But much of the geometric information, transformed into 'images', is present as backplanes of the cube. Software NIMS cubes were designed to be accessed by the ISIS system, which includes extensive software for generating, manipulating, analyzing and displaying them. ISIS exists in VMS and Unix versions, which must be obtained independently, as described in the documentation of this data set. But simple software for displaying bands, backplanes and spectra of cubes will be available by soon as an enhancement to the NASAview image display program, under development by PDS. It will be included with later versions of this data set. Media/Format The NIMS cubes and 'mask' images are archived on CD-ROM for delivery to the Planetary Data System (PDS). Formats are based on standards for such products established by PDS." END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = VENUS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = GO INSTRUMENT_ID = NIMS END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CARLSONETAL1992" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END