Introduction to ISIS

The planetary research community has moved into a phase in which virtually all scientists and cartographers must have access to basic planetary data in digital form. Technological developments now permit the dissemination of nearly the entire collection of planetary digital data to the community. As part of the Planetary Data System (PDS), the vast majority of the data are distributed on CD-ROM discs in raw form; no processing is performed other than organizing the original digital data into raster-formatted image files. In addition to expected enhancements in data quality and availability as a result of future space missions, continual improvements in techniques for image processing, geometric information on spacecraft position and pointing, and calibration data are anticipated. The highest level of data processing quality can be maintained by making continually improving image processing capabilities available to researchers. Here we describe the ISIS (Integrated Software for Imagers and Spectrometers) software system. ISIS is under development by the Astrogeology Program (AP) of the USGS in Flagstaff, AZ for use by the planetary science community. ISIS combines basic capabilities of image processing, analysis, and display of 2- and 3-dimensional (multispectral and hyperspectral) data with the specialized planetary cartographic functionality required for a variety of planetary science applications.

A Brief History of ISIS

The workhorse of the USGS Planetary Cartography effort over the last 20 years has been PICS (Planetary Image Cartography System), which is VMS-based software tailored for planetary digital cartographic production. Examples of major cartographic projects completed at the USGS using PICS are the Viking-based Mars Digital Image Mosaics (MDIMs), Venus Magellan Radar Maps (or "F-Maps"), Voyager-based controlled digital mosaics for all satellites of Jupiter, Saturn, Uranus, and Neptune, irregular satellite image bases including Phobos, Deimos, Gaspra, and Ida, as well as special products such as globes and wall charts.

ISIS was originally developed for the VAX/VMS operating environment, with interactive display capabilities requiring the use of an International Imaging Systems IVAS image display device. The original ISIS was intended to extend our expertise in data processing and analysis beyond the standard two (x,y) dimensions of PICS to the third (z) or spectral dimension. The VAX/VMS ISIS combines elements of classical image processing and spectral analysis with new techniques developed specifically for the analysis of image cubes. ISIS was specifically designed to facilitate analysis of data from hyperspectral NASA instruments such as the Galileo Near Infrared Mapping Spectrometer (NIMS) and the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS). Like the PICS software, the VAX/VMS version of ISIS is still available to users.

Beginning in the early 1990s, there has been a major effort within the AP to combine PICS functionality with that of ISIS, and to increase the efficiency and portability of the unified system by making it available on a variety of lower cost, UNIX-based computer platforms. The new software system retains the ISIS name but offers enhanced capabilities for interactive cartographic and scientific processing of monochromatic, multispectral, and hyperspectral image data or "cubes" (single-band images are viewed as single-band image cubes). ISIS provides an extremely powerful, user-friendly tool for processing, analyzing, and displaying digital remote sensing data. The data may be of virtually any size, and data types from a variety of Earth and space science missions are supported. Data are processed as image cubes in which a single spatial (X,Y) scene is represented in one or more spectral (Z) dimensions. The unique data storage capabilities of ISIS, in which additional data (image or non-image) may be stored as cube backplanes, sideplanes, and bottomplanes, also permit straightforward storage, display, and modification of ancillary information. ISIS will handle with equal ease the multiband spectral data from Clementine (11 bands) and Imager for Mars Pathfinder (15 bands), as well as the hyperspectral data of the Galileo NIMS instrument (408 bands).

ISIS Programming Priorities

The USGS Astrogeology Program is a major contributor of software for digital data processing in support of a variety of NASA programs, including the Planetary Cartography and Geologic Mapping (PCGM) Program, Code SL Flight Programs, Research and Data Analysis Projects, and the Planetary Data System (PDS). In planning and implementing the software development for ISIS, emphasis is placed on supporting data processing and analysis tasks for current and future NASA missions. Many ISIS programming efforts are in direct support of the PCGM Program and they focus on software development for cartographic data processing by the USGS and for science-oriented image processing by Planetary Geology Principal Investigators at their home institutions. Additional ISIS software development priorities include (1) ingestion and analysis of data from current and near-future NASA missions; (2) incorporation and refinement of programs and procedures from our older VAX/VMS-based PICS (Planetary Image Cartography System) software on an as-needed basis; and (3) data transfer and processing software to facilitate photogrammetric data processing with our Digital Photogrammetric Workstation. As a result of our involvement as cartographers and scientists in a variety of current and future NASA programs, the PCGM program and members of the Planetary Geology community enjoy the benefits of an integrated software system for sophisticated processing, display, and analysis of planetary remote sensing data.