some other fields that rely more on imaging data, where “lossy” data compression does not necessarily invalidate the data and may sometimes be desirable.
Federal data sets in the physical sciences that are candidates for long-term preservation can be classified into three generic types, for which illustrative examples are presented in this section:
Massive records and data from an original experiment, particularly a “mega-experiment,” that there is no realistic chance of replicating, even though it is, in principle, reproducible.
Critically evaluated compilations of data from a large number of original sources that represent tremendous accumulated effort.
Unique, perhaps time- and environment-dependent, engineering data collected at federal facilities or as part of a government project (that may or may not ever be completed), much of which never reaches the published literature.
Experiments carried out on a “grand scale” may become impossible to reproduce for many reasons, e.g., the sheer effort and cost involved, a change in societal circumstances, or the destruction of the apparatus (such as a unique particle accelerator).
Example 1: Atmospheric and Underground Nuclear Weapons Test Results
The Department of Defense (DOD) Nuclear Information Analysis Center —which goes by the acronym of its former name, DASIAC—is the Defense Nuclear Agency's (DNA) repository for information from nuclear weapons tests. Its holdings cover the entire era of nuclear weapons testing, including both atmospheric and underground tests, but only includes data that have been sent to DASIAC; which has no authority to claim data. DASIAC is not a mere repository, but rather has the explicit goal of keeping information in a form that is useful and accessible to interested parties.
DASIAC's data document the effects of nuclear explosions in contrast to the performance of the weapons per se. The latter information, which was the primary goal of the majority of tests, is the responsibility of the Department of Energy (DOE). Consequently, DASIAC's data holdings are just from those tests and experiments that were designed to evaluate the effects of nuclear explosions, perhaps 10 percent of the total number. Its holdings from atmospheric tests are currently more comprehensive than from underground tests.
The bibliographic citations of DASIAC's holdings (shelf lists) run to some 40 shelf feet. A more recent estimate was that the holdings, if all converted to electronic form, would require more than 2 terabytes of capacity. The collection is growing as people with long experience in nuclear effects testing retire, and the rate of accumulation is likely to accelerate with the end of the Cold War.
Some of the major blocks of the DASIAC holdings include some 300,000 pages of published reports (the definitive DNA documentation of tests in which that agency was involved); about 50,000 documents of historical literature; DNA research, still being added at a high rate; 9000 data sets resulting from tests for the semiconductor industry of the effects of nuclear explosions on electronic parts; 40,000 data sets related to electromagnetic pulses; 130,000 still photos and 17,000 motion pictures of blasts; and about 8000 cubic feet (a major bulk of DASIAC data) of data on thermal radiation and air blast shock waves. Many of the data are classified as restricted or formerly restricted so that, in accordance with the Atomic Energy Act, no automatic declassification is scheduled.
The data are stored on a variety of media in addition to the many paper records: silver disk, oscilloscope tracings, magnetic tape (not stored as required for good archiving practice), and photographic film. All the motion pictures are on safety film. Most of the holdings are in an environmentally controlled facility in Santa Barbara, California.
The data of interest to the physical science community cover such topics as:
Nuclear test detection, surveillance, control, weapon safety, and security.
Survival, vulnerability, hardness of military systems, civilian facilities, electronic and structural components.
Phenomena associated with the fireball, shock waves, fallout and radioactivity, electromagnetic pulse, atmospheric ionization, and electromagnetic propagation.