Inclusiveness of Major Research Foci to Which NASA Can Make a Unique Contribution

NASA is a proven leader in the development of imaging spectroscopy and is the U.S. civilian agency best suited to lead efforts for improved spaceborne IS. NASA’s strengths in developing new analytical techniques (e.g., to map subpixel compositional and temperature variations); processing terabytes of data rapidly; integrating derived data sets into numerical and statistical models; and distributing data, tools, and models to the community will also help the agency develop a capability to resolve spectral signals of interest and to monitor environmental changes continuously.

Strengths and Weaknesses of the SESWG Recommendations

The SESWG report recommends improving the precision and resolution of solar-reflected IS in the near term and continuous full-spectrum IS in the long term. However, the recommenddations are worded vaguely. We assume that the immediate objective includes continuation of the AVIRIS instrument, which is the only research-caliber aircraft system available. We also assume that the long-term mission is for a hyperspectral (less than 10-nanometer bandwidth) visible-near-infrared spaceborne IS. If these assumptions are true, implementation of the SESWG recommendations would yield the high spectral and high spatial resolution needed to address a wide range of applications. For example, doubling the spectral resolution to 5 nanometers in the solar-reflected part of the spectrum while maintaining a high signal-to-noise ratio (e.g., 1000) at other visible-near-infrared wavelengths could help detect constituents (e.g., organic material) or differentiate between mineral forms (e.g., fibrous versus nonfibrous) that are important for environmental monitoring and geologic mapping.46 Of course, improving spectral, spatial, or radiometric resolution would increase data volumes, so NASA will have to ensure that adequate resources are available to analyze these data.

On the other hand, not all science applications require high-spatial-resolution and high-spectral-resolution data. With 50 spectral bands MASTER (Moderate Resolution Imaging Spectro-radiometer [MODIS]/Advanced Spaceborne Thermal Emission and Reflection Radiometer [ASTER] Airborne Simulator)47 can meet at least some of the scientific objectives driving the immediate SESWG goal of an airborne capability in the thermal portion of the spectrum. Multispectral, moderate- to high-spatial-resolution instruments such as 30-meter Landsat are useful for broadly characterizing the land surface and for monitoring long-term trends on a global basis. A new Landsat mission would fall within the 1–5 year SESWG goal, yet NASA has no plans for continuing this capability in the immediate future.48 These instruments and the instruments proposed in the SESWG report would each meet different scientific objectives. However, if for financial reasons only one instrument could be flown, a hyperspectral instrument is the obvious choice because multispectral equivalent products can be extracted from hyperspectral data.

Another weakness of the SESWG report is the lack of specific recommendations for new technology and sensors; most of the discussion refers to refining existing techniques. For example, the thermal imaging spectrometer demonstration project recommended in the near term would require an order of magnitude improvement in spectral resolution. It is unrealistic to expect that the new sensor technologies needed for this mission will become available over the next five to ten years. Moreover, a technology demonstration mission could be expanded to include other technologies, such as microbolometer detectors that require no active cooling or constellation

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Clark, R.N., T.M. Hoefen, G.A. Swayze, K.E. Livo, G.P. Meeker, S.J. Sutley, S. Wilson, I.K. Brownfield, and J.S. Vance, Reflectance spectroscopy as a rapid assessment tool for the detection of amphiboles from the Libby, Montana Region, U.S. Geological Survey Open File Report 03-128, 2003, <http://pubs.usgs.gov/of/2003/ofr-03-128/ofr-03-128.html>.

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<http://masterweb.jpl.nasa.gov>.

48  

NASA cancelled its request for proposals for a Landsat data continuity mission, which will lead to a data gap. See <http://ldcm.nasa.gov/>.



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