Trends in the Acquisition and Accessibility of Long-Term Solar-Terrestrial Data

Abstract

Solar-Terrestrial Physics (STP) programs involving global data acquisition have characterized international science in the 20th Century and made necessary the creation of a system of national and international data centers. Under aegis of the International Council of Scientific Unions, the World Data Center (WDC) system was established in 1957 to provide a voluntary mechanism for the collection, copying, exchange, and dissemination of geophysical and solar data taken by International Geophysical Year projects. At first, WDCs collected mainly analog data recorded by monitoring arrays of IGY instruments. In the three decades since IGY, techniques shifted from mainly analog recording to digital, and data centers shifted from mainly servicing analog images on film and publishing summary tables to providing numerical data on digital media for computer analysis.
In the 1960s, WDCs began to provide collection and dissemination of information and derived data products as well as original data. During the late 1970s, merged multi-component data sets were created on central host computers to support joint analysis projects by groups of scientists and individuals. A major trend in the late 1980's is acquisition and merger of large digital data sets from ground-based and satellite sensors. The data are made available on high density computer media (particularly CD-ROM optical discs) together with summary analog images and access software for browsing or moving data from the storage media to other computers. Tables and images are still published in the 1990s and are especially needed in places with limited access to personal computers and lacking easy connections to on-line central data collections.
The cumulative amount of STP data held by WDC-A has grown substantially since 1957. However, each year since the early 1960s has shown a decline in the global coverage of key types of data as monitoring networks diminished. The rise in cost to process large digital databases produced by modern instruments and the high cost of labor-intensive analog data reduction has contributed to the annual decline of some types of data deposited with the WDCs. Finally, there is a situation that is difficult to quantify; namely, some key geophysical observing sites are located in countries that seldom use their output. During periods of economic stress these facilities receive low priority for continued operation. Under current world conditions, it is difficult for some nations to justify the continued expense to continue operating basic monitoring sites, e.g., magnetic observatories, ionosondes, and other instruments that produce essential records needed as input for general models, planetary indices, or other often-used, basic global data products.