Data Format - Data types - Data Labels - NIMS Guides - Data Access - More info

Data Format

All data files have PDS labels. The raw data (EDR) file (on a different CD-ROM series: GO_10xx) contains time-sequential, 16 bit integers. Reduced data files (cubes of various kinds) may be viewed as images or spectra. They contain VAX real numbers, are band sequential (BSQ - the images are stacked in band order) and have geometry information appended as backplanes after the last NIMS band.

Data Types

Mask files contain summary images (3 band BSQ) and spectra of up to six selected regions that provide a quick indication of data location, data quality and spectral content. A Guide to understanding the NIMS mask is available.

G-cube (or Mosaic) files contain data that have been projected and resampled. The core data are band sequential (BSQ) - spatial in the first two dimensions, and spectral in the third. Cubes of the satellites are projected in point-of-view, and, with few exceptions have no photometric correction applied. Cubes of Jupiter are (generally) projected as simple cylindrical. Cubes of Europa, Ganymede, and Callisto have been despiked. The cubes are available both in radiance and I/F (intensity divided by flux) form.

Tube files contain data in (almost) time order and normally have a NIMS-instrument-related 20 pixel spatial dimension (20 x n or n x 20). Projection coordinates are contained in backplanes, but the data have not been resampled. Tubes are availiable in both radiance and I/F form. Despiking has NOT been applied. All data in cubes are also available in tube form. Some data (such as spatially undersampled data, limb scans and flight calibrations) appear in tube form only.

A spike file contains a list of pixels that have been identified as spikes, but not replaced, in the tube. Spike files can be used to remove spikes from both tube and EDR files.

EDR files contain the most primitive form of the data available. They should be used only for advanced data analysis. The format is complex and the files do not form images or spectra without prior processing

Data Labels

A data label (PDS form) is attached to the front of each file (except masks, which have a detached PDS label). The labels are in ASCII keyword=value format and contain pointers to various data objects in the file, descriptions of the data objects and descriptions of the observation associated with the file. A history object in similar format follows and describes the processing steps that produced the file. Much of this information is necessary for understanding and viewing the cube. In particular, the label contains the offset to the cube, the dimensions of the cube, axes labels, and explicit wavelength information.

NIMS Guides

NIMS Guides provide descriptive information about each orbit, the planned observations within each orbit and the data return. (Not all data from each planned observation could be returned.) The observation description includes planned geometry and observation intent. The guides on this CD-ROM are in postscript format, one file per chapter.

Data Access

Software for processing this data is called ISIS and is available for DEC VAX VMS, SUN Solaris, DEC Alpha Digital Unix, Silicon Graphics Unix and PC LINUX systems. Images from NIMS cubes and tubes can be viewed with any image display program which allows an offset from the beginning of the file to the selected image. Packages tested include ISIS, VICAR, ENVI, SAO IMAGE, and NASAVIEW. ISIS and ENVI (and soon NASAVIEW) additionally display spectra. The ISIS viewer is named CV (UNIX) or QL3 (VMS). (See CONTACTS for help in obtaining software.)

Labels may be displayed with some editors (eg DOS edit), and with most "type" and "search" functions. Some editors do not recognize the PDS line termination conventions. The label may be listed by the ISIS function LHLIST (VMS) or LABELS (UNIX).

Software for converting EDRs to cubes exist in both ISIS (DEC VAX VMS) and VICAR (DEC Alpha VMS) versions only. A primitive list of values in an EDR may be obtained with the program EDRDMP2, available from the NIMS team.

More Info

A much more complete description of the instrument, data formats, and data labels may be found in VOLINFO.TXT files on both EDR and CUBE CD-ROMs. It is strongly recommended that you read AAREADME.TXT and VOLINFO.TXT on this CD-ROM, plus the NIMS Guides to the relevant Galileo encounters with Jupiter, before requesting additional help. See CONTACTS if you still need help.