product is available for the Global Land Survey 2000, 2005, and 2010 collections and is generated on demand from Landsat 4-5 TM and Landsat 7 ETM+ data.9 The concept would gain additional utility through a formal but open mechanism for identifying candidate products and the resources needed to produce them.

Although the concept of a climate data record (CDR) has surfaced numerous times in recent National Research Council reports,10 the climate research and policy communities continue to struggle with an exact approach to meet this need (i.e., one that is both sufficient and cost effective). In addition, satellite-based CDRs have been further segmented into the following:

Fundamental climate data records (FCDRs) are calibrated and quality-controlled sensor data together with documentation for the data used to calibrate them.

Thematic climate data records (TCDRs) are geophysical variables derived from the FCDRs that have well-defined levels of uncertainty, with an ongoing program of correlative in situ measurements required for validation.

Essential climate variables (ECVs) are atmosphere, ocean, and land measurements derived from FCDRs and TCDRs. They have to be technically and economically feasible for systematic observation and sufficient to meet the needs of the United Nations Framework Convention on Climate Change and the Intergovernmental Panel on Climate Change (IPCC). To be useful, the ECVs must be a time series with sufficient length, consistency, and continuity to identify climate variability and change.

This report has looked at observations that would be available from SELIP from the perspective of the needs of users and engineering units (spectral, radiometric, spatial and temporal resolutions, and so on). The committee recognizes both the challenge and the need for SELIP to work with key related communities to develop an agreedon set of FCDRs, TCDRs, and ECVs based on moderate-resolution sensors. That will mean going beyond the engineering units, such as calibrated radiance, in the existing Landsat archive, embracing more broad units—such as surface reflectance, surface temperature, cloud, and cloud shadow—and eventually evolving to more application-oriented products (i.e., ECVs). These products will also need to meet the Global Climate Observing System, First National Climate Change Communication, and IPCC requirements and be technically and economically feasible systematic observations. The Landsat Surface Reflectance product is an excellent example; it is produced routinely for selected time periods but is also available on demand for specific Landsat scenes.

ALGORITHM DEVELOPMENT AND CALIBRATION/VALIDATION

As the focus in Landsat and other space or airborne data acquisition systems evolves from providing imagery to providing higher-level data products derived from those images, a set of consequent activities becomes necessary. The first step is to develop a rigorous process for determining the required data products, similar to NASA’s elicitation of requirements for Moderate Resolution Imaging Spectroradiometer (MODIS) data products or the development of the essential climate variables. Once a set of desired standard data products has been determined, the algorithm for producing the data product is selected, reviewed, and implemented. Models for this process exist in the federal and private sectors—ranging from proprietary development in house to open, competitively selected development. Regardless of the model, the selection, development, and distribution of algorithms are best achieved with freely and openly available data. Transparency of algorithms provides credibility and allows a larger community to participate in evaluation and continuous improvement.

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9 U.S. Geological Survey, Product Guide: Landsat Climate Data Record (CDR) Surface Reflectance, Version 2.0, 2013, available at http://landsat.usgs.gov/documents/cdr_sr_product_guide.pdf.

10 See the following National Research Council (NRC) reports: Climate Data Records from Environmental Satellites (2004); Adequacy of Climate Observing Systems (1999); Ensuring the Climate Record from the NPOESS and GOES-R Spacecraft: Elements of a Strategy to Recover Measurement Capabilities Lost in Program Restructuring (2008); Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond (2007). Each report was published by National Academy Press (after mid-2002 The National Academies Press), Washington, D.C.



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