NASA Satellite Systems for the Non-renewable Resource Sector
By James Ellis
NASA's Earth Observation System's best kept secret is that two satellites, scheduled for launch in 1999, offer truly superior spatial and spectral resolution, pricing, and sensor calibration for the non-renewable resources sector (oil & gas and minerals). These satellites are Landsat 7 and ASTER. In addition, three other NASA missions offer new mapping capabilities to the non-renewable sector: a space shuttle radar mission in September 1999 will generate a near-global digital elevation map (DEM), the EO-1 spacecraft is to be launched in December 1999 and will carry new test instruments designed to reduce future costs and expand spectral range, and a radar satellite (LightSAR) is to be launched 2002 that offers exceptional geological information.
The MapFactory, through its professional services and production subsidiary, HJW, will be using these satellite systems to generate basemaps, improve geologic maps, plan field operations, monitor environments, and minimize impact for the non-renewable resource sector. These satellite sensors will also help focus airborne photographic, multispectral, and hyperspectral surveys for a variety of applications.
Enhanced Landsat 5 TM imagery of Asia showing remarkable geology. These color images were created by combining on visible-light band with two reflected-infrared light bands (TM bands 7, 4, 2 as red, green, blue).
Commercial satellite systems such as Landsat 5, RADARSAT, SPOT, IRS, and ERS; plus IKONOS, OrbView, and Quickbird (upon successful launching) will have a fundamental role in building up-to-date and accurate basemaps, databases, and interpretations for the non-renewable resource sector. These satellites enable managers, geologists, engineers, and environmental specialists to reduce risk, improve maps, and enhance communications with shareholders, partners, agencies, and landowners.
The oil & gas and minerals industries have relied heavily on the global coverage of Landsat Thematic Mappers (TM) 4 & 5. The MapFactory recently utilized over 85 Landsat TM scenes to generate an up-to-date and accurate foundation for a country-wide GIS of Mongolia. There are, however, limitations with the remaining TM system, Landsat 5, which are significant, including a perceived high cost for imagery less than 10 years old, gaps in recent global coverage, spatial resolution limitations (improving it requires imagery from other satellites), spectral limitations (one short wave IR [SWIR] band and one thermal IR [TIR] band) that limit interpretation of geology, and a lack of DEMs.
The Landsat series offers some stereoscopic overlap in higher latitudes, but other satellite, aircraft, or topographic maps have to be utilized to develop DEMs. SPOT has a DEM-generating capability that is globally limited by cloud-cover. The radar satellites are being used to generate DEMs, but the cost for many companies in the non-renewable resource sector is excessive. A consistent, global, high-resolution DEM is not available to improve interpretations, modeling, and basemaps.
The limitations of Landsat 5 and the lack of a global, high-resolution DEM will be addressed with successful launches of Landsat 7, ASTER, and Space Shuttle Atlantis radar during 1999.
Landsat 7 will have the same 7 bands as previous TM sensors. However, it will also have a new black-and-white band with 15 meter spatial resolution that can be readily used for sharpening 30m color composites acquired at the same time. Landsat 7 will be able to acquire images globally without need for the satellite being in sight of a receiving station. Landsat 7 is not "privatized" as Landsats 4 and 5 were, therefore, the cost of Landsat 7 imagery will be significantly less. Landsat 7 data will be made available to all users through the U.S. Geological Surveys' EROS Data Center (EDC) at the cost of fulfilling user request. Value-added providers for the non-renewable sector will have significant opportunity to furnish enhancements, interpretations, and specialty products without fear that the government will undercut their offerings.
Landsat 7 applications will be similar to Landsats 4 and 5 in mapping regional geological features, interpreting near shore hazards and bathymetry, planning pipelines, establishing environmental baselines, and monitoring impact.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer satellite is scheduled for launch 15 July 1999. The ASTER instrument is on the EOS AM-1 platform that hosts four other sensors. ASTER is heavily publicized as an integrated calibration sensor onboard the EOS AM-1 platform. That being true, however, it is obvious from examining the spectral channels that ASTER was designed by remote sensing geologists for geology. ASTER offers an entirely new satellite-based capability. ASTER images will be collected in 14 channels-four span the visible, near IR (VNIR with 15m spatial resolution), five cover the SWIR (with 30m spatial resolution), and five cover the TIR (with 90m spatial resolution). ASTER is a unique breakthrough for spaceborne geologic mapping. SWIR Imagery Five ASTER bands (#5-9) cover the SWIR range. Band 6 is centered on a clay absorption feature (often associated with hydrothermal alteration and improved mineral potential). Band 8 is centered on a carbonate feature, allowing global discrimination of limestones and dolomites from other rocks. Information contained within the 5 bands can be enhanced through band ratioing, principal components, and other image processing manipulations.
Landsat 7 and ASTER, along with the space shuttle DEM, will improve upon color images like this, providing increased spectral, spatial, and elevation information.
Five ASTER bands (#10-14) cover the TIR range. Bands 10, 11, and 12 are designed for detection of sulfates and silica spectral features. Evaluating reflectance patterns seen in SWIR band 6 with TIR band 10 will allow discrimination between common minerals such as alunite, a sulfate mineral important to precious metal deposits, and anhydrite, an evaporative sulfate common in arid regions. Band 14 is centered on a carbonate spectral feature, complementing information in SWIR band 8. Together the TIR bands are capable of discriminating lithologies, compositional variations among rock types, and areas of hydothermal alteration. Unlike Landsat TM, ASTER will also be available for night-time TIR acquisitions that would markedly improve interpretations.
Near-infrared, black-and-white stereo images with 15m spatial resolution can be acquired by ASTER's band 3. These stereo images are obtained along the orbital track and can be interpreted with stereoscopes as the base-to-height ratio is a very favorable 0.6. The stereo pairs can also be used to produce DEMs with 10m to 50m accuracy in x,y,z dimensions using commercial photogrammetric/image processing software. Topographic maps with scales of 1:100,000 and perhaps 1:50,000 will be supported by ASTER DEMs. However, it is estimated that only 1 DEM will be produced out of the approximately 310 images that will be processed daily. Users should be able to acquire stereo images from EOSDIS and build their own DEMs using commercial software, opening up opportunities for value-added providers in the natural resource sector.
ASTER will have a revisit time between 4-16 days. Day and night imagery is planned, enhancing the value of TIR capability. Each scene will cover approximately 60 x 60km. The instrument can collect data for an average of only 8 minutes per orbit. Over its 5 year mission, this translates into approximately 1/2 million stereo pairs. ASTER will be capable of acquiring the 45,000 cloud-free, digital stereo pairs required to cover the entire land surface of the Earth. The non-renewable resource sector's need for SWIR, TIR, and DEMs will be addressed with this remarkable global coverage.
The data should be free from EOSDIS. Imagery is scheduled to become available 6 months after launch, approximately 15 January 2001. The commercial remote sensing community needs to be able to successfully and easily access ASTER data through EOSDIS if the satellite is to be useful for the non-renewable resource sector.
ASTER applications will be numerous, including: mapping hydrothermal alteration zones, upgrading geologic maps created from other multispectral satellite sensors, stereoscopic interpretation of sophisticated and complex geological images, generation of high-resolution DEMs for structural geology altitude determinations (strike, dip, and plunge) and for corridor planning, as well as new research and development on environmental uses of this unique imagery.
Space Shuttle Radar
The most complete high-resolution DEM of the Earth is to be acquired between 16-27 September 1999 by STS-99 Shuttle Atlantis. It will take about 1 year for the DEM to be produced. The DEM will span the globe between 60 N to 56 S latitude. The vertical accuracy should approach 10m relative and 20m absolute.
The full resolution DEM grid is 30m. This will be available across the U.S. However, outside the U.S. access to the full resolution DEM is under the control of the Department of Defense. Guidelines about archiving and use are provided in a NASA/NIMA memorandum of understanding. A 90m grid will be available globally without restrictions.
The near-global DEM will have several applications, which will include: serving as the 3D base upon which enhanced multispectral imagery can be draped to create highly informative perspective and stereoscopic views of the Earth's surface, enhancing structural geology and subtle topographic features through artificial illumination, integration with bathymetric datasets to improve understanding of the entire Earth's surface.
In December 1999 the EO-1 spacecraft is to be launched with two instruments of interest to the non-renewable resource sector-the Advanced Land Imager and Hyperion.
The Advanced Land Imager will test new concepts that reduce cost, mass, and complexity for future replacements to Landsat 7. The satellite will image the same ground area as Landsat 7 once or twice a day. It will mimic the 6- 30m Landsat 7 bands, but will also record 3 more bands. One is a very short, blue light wavelength band that could improve penetration of water and bathymetric mapping, if not overly susceptible to atmospheric scattering. The other 2 bands are in the SWIR range.
The Hyperion instrument is a hyperspectral sensor with 220 bands recording reflectance between visible blue and SWIR light (0.4-2.5 micrometers). Each scene will cover 7.5km x 100km.
An all weather, day-night radar sensor, LightSAR is to be launched sometime in 2002. This satellite may be able to measure features 1m to 3m across with a revisit interval of 8 to 10 days. The system will use a relatively long radar wavelength (L) compared with most radar sensors, enabling new information to be extracted from the imagery. LightSAR will have a 25m spatial resolution. Most importantly, it will be capable of multiple polarizations, including "quad" polarization that will significantly improve interpretation of geologic features.
Applications for the non-renewable resource sector will include: offshore oil seep and spill detection, reinterpreting geology on a global scale to account for characteristics detected by L-band radar that are not detected with conventional imaging and mapping tools, and establishing an environmental baseline and monitoring changes in areas covered with clouds, haze, and smoke.
When Landsat 7 and ASTER are operational, and the geologic remote sensing community has access to the archives, significant improvements will be made in non-renewable resource planning, minimizing the environmental impact of field operations, mapping, and interpretations. Landsat 7 and ASTER greatly improve the spatial and spectral resolution currently available to geologists. Both systems promote opportunities for value-added providers through minimal data cost and minimal government enhancement of data. The availability of Landsat 7 and ASTER data will help focus airborne multispectral and hyperspectral surveys for a variety of applications, including mapping of non-renewable resources.
STS-99's near-global DEM mission will provide geologists and environmentalists working in the non-renewable resource sector a uniform, high resolution DEM for improving interpretations, modeling, and basemaps beginning in mid-2000. It is hoped that the exciting data from the EO-1 sensors will be made available to the industry beginning in 2000. LightSAR imagery will significantly improve geologic mapping when it is available sometime in 2002.
The prospect of integrating data derived from these new NASA satellite systems with imagery purchased from commercial satellite systems such as RADARSAT, SPOT, IRS, ERS, IKONOS, OrbView, and Quickbird will improve the available data for mapping, databases, and interpretations. Both government and commercial satellite systems will be needed to fully address the needs and requirements of the diverse and global non-renewable resource sector.
About the Author:
James Ellis provided remote sensing solutions for 15 years with an international petroleum company prior to helping start-up The MapFactory in 1997. He is focused on broadening the customer base for satellite and airborne remote sensing technology and teaming with his company's professional services partner, HJW.