The Role of Small Satellites in NASA and NOAA Earth Observation Programs (2000) / Chapter Skim
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2 Core Observational Needs
2 Core Observational Needs
Pages 11-21
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From page 11... ...
On the other hand, some operational data sets do meet climate research needs, such as the NOAA POES and Geostationary Operational Environmental Satellites (GOES)
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From page 12... ...
Operational data also play an important role in numerical weather prediction lit is expected that the 24 EOS measurements discussed here a set maintained during several previous program rescopings will now change as NASA rethinks its plans beyond the first series of EOS spacecraft in light of this study's findings. 2See the sections on calibration and validation later in this chapter.
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From page 13... ...
In contrast to the Earth science missions, the primary users of operational data tend to rely on recently collected data rather than analyses of historical data. Moreover, the emphasis on specific application needs generally results in less interest in complex sensor suites to study a wide variety of Earth system processes.
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From page 14... ...
Suspended matter Total water content Cloud base height Cloud cover and layers Cloud effective particle size Cloud ice water path Cloud liquid water Cloud optical depth and transmittance Cloud top height Cloud top pressure Cloud top temperature Surface albedo Downward longwave radiation at the surface Insolation Net shortwave radiation at the top of the atmosphere Solar irradiance Total longwave radiation at the top of the atmosphere Land surface temperature Normalized difference vegetation index Snow cover and depth Vegetation and surface type Operational Requirements Document.3 For example, some of the service branches of the Department of Defense (DOD, which is NOAA's partner in the NPOESS program) require constant ground resolution imagery.
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From page 15... ...
Each measurement has its own set of performance and sampling requirements that are appropriate for a specific application. In general, sensor performance requirements for climate and global change research are more stringent than operational requirements, while the operational requirements for sampling and continuity are more stringent than the science requirements.
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From page 16... ...
For example, small increases in global sea surface temperature represent an enormous change in the heat content of the world ocean, and they are a valuable diagnostic of climate models. However, drift in sensor calibration or sensor performance could easily mask these changes.
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From page 17... ...
The committee notes, however, that satisfying many of the NPOESS operational requirements will necessitate comparisons between present measurements and climatologies derived from long-term observations. As undetected shifts in sensor performance may substantially reduce the quality of the operational product, regular assessments of instrument performance should be part of the calibration program.
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From page 18... ...
The complex challenge of how to achieve technical renewal while maintaining data continuity and quality can best be addressed by embracing a concept the committee calls dynamic continuity. Specifically, the quality and continuity of measurements must be transparent to three levels of changes: · Between successive flights of the same instrument design, · Between successive generations of instruments, and · Between similar instruments fielded by different countries.
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From page 19... ...
will provide nearly simultaneous observations in the infrared and visible portions of the spectrum for studies of cloud properties and illustrates the simplest level of integration necessary to achieve simultaneity. More difficult challenges in achieving simultaneity arise when data streams from multiple sensors must be combined either to derive a geophysical quantity or to study specific Earth processes.
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From page 20... ...
These include instrument calibration, prelaunch sensor characterization, data record continuity, simultaneity, and sampling strategies. All of these issues influence mission architectures for small satellites, although the research and operational user communities may assign differing importance to them.
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From page 21... ...
Although this chapter's discussion takes essentially a research perspective, the time sampling strategy of operational missions such as NPOESS could also be analyzed rigorously. If the EDRs were prioritized, a strategy different from the present small constellation of three medium-sized platforms might result.
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