E. The Modern WDC System: Opportunities and Problems
Experience has shown that many features of the original IGY WDC system are still useful, while others are obsolete. As the WDC system evolved and data holdings grew, the principle of multiple data sets had to be modified. Routine exchange of data between WDCs continued in a few disciplines in which it was well established and not particularly burdensome, but it ceased to be general practice and could not be extended to newer types of data, for several reasons.
First, it became impracticable to duplicate the large data sets obtained from spacecraft, because of the physical size of the archives, and the fact that the cost would be well outside the WDCs' budgets. This outweighed concerns about possible catastrophic loss. Second, many spacecraft and some other data sets carry privileges of "first use" by the experimenters whose instruments acquired the data, at least for a specified period of time. Third, it is often more practical for large data sets to be archived at the experimenters' home institutions. In this case, the WDC system can often act in a "referral mode," by holding information about data sets, though not the actual data. This extension of WDC services benefits experimenters and users by increasing the flow of information, and enables the WDC staff to serve the community more effectively.
Some of the problems have been solved by establishing National Data Centers, which may be collocated with a WDC and share the same staff. The data in such Centers are generally available to the international community, though their use may be subject to certain rules, and they carry no rights of free or cheap copying to other WDCs.
WDCs have developed new activities to support their basic purpose of providing data. They need to maintain contact with their user communities. Personal visits by users are encouraged, and some WDCs have guest scientist programs for extended visits. Some WDCs organize workshops to discuss data-related topics or undertake cooperative analysis of particular data sets by groups of scientists, e.g., the Coordinated Data Analysis Workshops (CDAW) of WDC-A. Such workshops are effective in promoting scientific interaction and good use of data.
Some WDCs have expertise for data processing services and compilation of data products. An example is the derivation of the much-used Auroral Electrojet (AE) magnetic index, originally undertaken by WDCA and later transferred to WDCC2, which also derives the equatorial Dst index. Another development is the production of joint catalogs in several disciplines. This was initiated in a joint WDCA and WDCB catalog for Geomagnetism, Report UAG86 of 1982, later replaced by Report UAG92 of 1985 which catalogued the holdings of the A, B, C1 and C2 Centers. A similar catalog was issued for ionospheric data, Report UAG91 of 1985 for Ionospheric Vertical Soundings data at A, B, C1 and C2. The catalogs are widely available on-line, and WDC information is increasingly available on the Worldwide Web (Section F). The success of these developments, and indeed the quality of all WDC services, depend on the work of the WDCs' scientific staff. The staff may engage in personal scientific research using the data, often in cooperation with the outside user community.
In general, WDCs do not provide operational services such as short-term forecasting or real-time reporting of geophysical or environmental conditions (e.g., of geomagnetic disturbances). These are undertaken by FAGS services or other organizations, though some WDCs do contribute to these activities.
Today's WDC system faces many challenges. It has to serve international research programs that aim to describe the complex and interactive Earth system, with the ultimate goal of predicting its evolution and future state. The major ICSU programs are the Solar-Terrestrial Energy Program (STEP, 1990-1995), the International Geosphere-Biosphere Program (IGBP, 1991-2000), and the International Decade for Natural Disaster Reduction (IDNDR, 1990-1999). Of these, STEP is in a field long served by WDCs and will provide work for WDCs long after the experimental phase has ended. The others embrace disciplines and types of data not hitherto familiar to the WDC system, such as the biospheric and humanactivity data needed for global change studies (e.g., maps of soil types, vegetation types and landuse), that may be non-numerical and non-continuous and thus require new analysis techniques.
The ICSU programs require the unrestricted exchange of solar, geophysical and environmental data, in order to describe the present state of Earth's climate and biospheric systems, to understand the workings of myriad individual physical and biospheric processes involved in the global system, and to monitor the progressive effects of those processes. The WDC community must always be on guard against attempts by national or commercial interests to restrict the flow of data. There is increasing difficulty, which is by no means confined to developing countries with their special problems, in maintaining the flow of data from the regular monitoring networks (e.g., geomagnetic, ionospheric and cosmic ray monitors). Even where networks are maintained for operational needs, as in meteorology, difficulties may arise in acquiring and preserving their data for long-term research.