Cycle Data Management," below). To fulfill their DAAC mission, however, they must also be responsive to scientific needs in a dynamic environment.
The ORNL DAAC neither manages satellite data nor works with EOS science and instrument teams, even though its in situ data sets are critical for calibration or validation purposes. Thus, by the definition given above, the ORNL DAAC operates more like a data center than a DAAC. Similarly, if the backup plans of the science teams are adopted, few DAACs will ingest or process EOS data. Those that do not will no longer be DAACs in the sense originally envisioned by NASA.
The DAACs have a dual role within the Earth Science Enterprise. Not only do they operate as discipline centers that serve the needs of a relatively small, specialized constituency, they cooperate as elements of a larger system, which serves the broader earth science community. The former must be a primary role—otherwise the DAACs cannot operate as effective data centers. The latter is an additional responsibility of the EOSDIS DAACs. Fulfilling the second of these roles is difficult because the DAACs are profoundly different from one another. Comparison of Chapters 3 through 9 indicates the following differences among the DAACs:
Their core constituencies are different. The discipline focus is different for each DAAC (Table 1.2), but even DAACs with overlapping disciplinary interests serve a distinctive set of users. For example, the ASF DAAC serves sea-ice scientists interested in synthetic aperture radar data, whereas the NSIDC DAAC serves the broader polar science community. Similarly, the EDC and ORNL DAACs serve terrestrial ecologists, but the EDC DAAC focuses on users of remote sensing imagery, and the ORNL DAAC focuses on users of in situ data from field campaigns and process studies.
Different disciplines place different demands on the information system. For example, the cryospheric studies facilitated by the NSIDC DAAC require polar projections, and the field-based data of the ORNL DAAC require a broader metadata model than would be developed for remote sensing data alone. In addition, the standard EOSDIS data format, HDF-EOS, is poorly suited for ASF and ORNL DAAC holdings, and the three HDF data structures supported by the ECS—point, swath, and grid—do not apply to all LaRC DAAC data.
They are hosted by a diverse array of institutions. The GSFC, LaRC, and EDC DAACs are housed in government-operated facilities, the ORNL DAAC and the PO.DAAC are located in facilities managed by private institutions, and the ASF and NSIDC DAACs are housed in universities (Table 1.2).
They vary in size. In terms of the size of the budget and the number of staff, GSFC is among the largest and ORNL is the smallest of the DAACs