Earth’s resources. These groups typically require custom data sets and comprehensive user services. Some of these users are served by the Distributed Active Archive Centers (DAACs), but increasing numbers are served by short-term, focused programs such as Earth Science Information Partners (ESIPs) and Regional Earth Science Applications Centers (RESACs).

Tables 2.2 and 2.5 in Chapter 2 indicate that both the earth and space science active archives serve a large user community. The DAACs supplied data to more than 104,000 unique users in FY 2000,2 greatly exceeding even NASA’s original expectations. The number of space science users is more difficult to determine, because some of the active archives only count Web site hits, which are considerably higher than the number of data requests. Nevertheless, it is clear that there are many tens of thousands of space science users. Using the membership of the American Geophysical Union as a proxy for the size of the earth and space science community (38,000 members from 115 countries),3 it is apparent that the data facilities and services serve more than just NASA investigators.

As noted above, the user community—especially of the DAACs—is quite diverse and thus is challenging to characterize in detail. All DAACs track electronic address extensions (e.g., .com, .edu, and so on) as a general measure of who accesses a site or obtains data. Figure 3.1 shows that scientists and government agencies—the highest-priority users—make up only a small fraction of total DAAC users. This observation highlights the importance of paying significant attention to the needs of the nonscientific community. Although the DAACs are aware of the broad characteristics of their user communities, a recent National Research Council (NRC) report found that few DAACs have a detailed understanding of their user profiles.4 The task group’s survey (see Appendix C) found the same still to be true.

The task group was unable to obtain user statistics on most of the space science active archives. However, based on the response of these archives to the task group’s survey, they appear to use similarly inadequate metrics to characterize their user communities. Some centers (e.g., Solar Data Analysis Center [SDAC]) do not even keep track of IP addresses and thus do not know the size or composition of their user community. All of the centers should know this basic information. A better understanding of their user profile would help them know whether it is scientifically necessary to expand the user base or provide new specialized services. The task group recognizes, however, that obtaining this information would increase operational costs and would require a re-evaluation of priorities by the supporting NASA office.

In the earth sciences, some specialized products and services are provided by ESIPs. The ESIPs were created in 1998 in part to develop value-added products from EOS and related data and to provide data services that are not being provided by the DAACs.5 Like the DAACs, the ESIPs track users by electronic address extensions, which provides only limited information about users. Using this categorization, the breakdown of users in the first quarter of 2001 was as follows: 33 percent education, 17 percent government, 14 percent commercial, 0.2 percent


The actual number of users might be slightly lower, since many scientists use more than one DAAC (see the results of a user survey in National Research Council, 1998, Review of NASA’s Distributed Active Archive Centers, National Academy Press, Washington, D.C., p. 215–229).


American Geophysical Union members represent the fields of atmospheric and ocean sciences, solid-earth sciences, hydrologic sciences, and space sciences. See < >.


National Research Council, 1998, Review of NASA’s Distributed Active Archive Centers, National Academy Press, Washington, D.C., 233 pp.


For a list of ESIP products and services, see < >.

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