What Happens to the Data?



EOS Data and Informaiton System (EOSDIS)

The EOS Data and Information System (EOSDIS) is being developed to fulfill the role of compiling, archiving, and distributing the EOS data. At present, EOSDIS manages data from NASA's past and current Earth science research satellites and field measurement programs, providing data archiving, distribution, and information management services. During the EOS era, EOSDIS will command and control satellites and instruments and will generate useful products from orbital observations.

The Earth Observing System Data and Information System (EOSDIS) is a comprehensive data and information system designed to perform a wide variety of functions in support of a diverse national and international user community. The EOSDIS is a fundamental part of NASA's Earth Observing System, and will include data from instruments on EOS spacecraft, airborne and ground-based instruments, and existing data sets. EOSDIS services include: user support; data archive management and distribution; information management; data and information product generation; spacecraft command and control; and data capture and telemetry processing.

Data quality for EOS is ensured through activities in three areas: calibration, validation, and quality assurance. The primary objective of EOS calibration and validation activities is to characterize and document the accuracy and precision of EOS observations and derived biophysical and geophysical products over all relevant temporal and spatial scales.

Calibration activities will characterize and document measurement accuracy and precision of the EOS instruments.

Validation activities will determine the uncertainties associated with EOS geophysical data products. The uncertainty estimates are obtained primarily through comparisons with independent measurements of the same geophysical parameters. To obtain independent observations, EOS interdisciplinary and instrument investigators will utilize: 1) surface test sites; 2) field experiments involving land-based, ship, aircraft and satellite observations; and 3) existing national and international observation sites and measurement networks.

Quality assurance activities will identify and flag data products that clearly do not conform to the expected accuracy for the particular product. Automatic identification algorithms will be provided to detect data that fall outside of specified allowed ranges.

EOSDIS Data Processing & Archiving Centers, located throughout the United States, are responsible for distribution of all EOS-related data. World Wide Web homepages for these centers are located at http://eospso.gsfc.nasa.gov/eos_homepage/data.html.

Data go through many levels of processing before becoming useful to scientists. Following are the levels needed to make an image like you see in this CD-ROM.

Raw Data: Unprocessed data in their original packets (data streams), as received from the instrument on the satellite.

The following levels of data are pictured on the left:

Level O: Raw instrument data at original resolution, time ordered, with duplicate data removed.

Level 1: Time referenced instrument data at full resolution that has been radiometrically corrected with calibration coefficients, located by position on the Earth, and converted to a scale-line or image format.

Level 2: Derived geophysical parameters at the same resolution and location as the Level 1 data. At this point, the data are still in "strips" that trace the path of the satellite's orbit.

Level 3: Geophysical parameters that have been spatially and/or temporally resampled (i.e., derived from Level 1 or Level 2 data). This is a fully-processed product on a regular geographic grid and with consistent time slices.

Level 4: Model output and /or results of lower level data that have been processed to generate "value-added" products that are not directly derived from the measurements.

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