individual investigators represent the most decentralized approach. Other efforts adopt a project-oriented, more centralized approach that involves neither individual investigations nor discipline data centers. For example, NASA has both centralized and decentralized approaches to archiving.

In planetary science, it is now customary for data first to flow from individual investigators and projects to distributed discipline data centers. These discipline data centers in turn provide data to the Planetary Data System, which manages the archiving process, fulfills data requests, develops standards, and provides directory information. Space physics is attempting to emulate this system, but other disciplines, such as the life sciences, seem to favor a more centralized approach, while astrophysics favors a hybrid approach with some centralized and some decentralized efforts. The data in NASA then traditionally flow to the National Space Science Data Center for more permanent archiving.

In other agencies the data pathways—dataways, in analogy to the nation's waterways—do not appear to be as highly developed as NASA's dendritic channels. For instance, NOAA's National Geophysical Data Center (NGDC) tends to work directly with investigators and not through intermediaries. Federal laboratories, such as Los Alamos National Laboratory (LANL) and Lawrence Livermore National Laboratory (LLNL), tend to produce their data internally and not seek them from external sources. Ultimately, the most important of this information should pass down the dataways to permanent archives, but little of it presently does. Thus, one of the panel's major objectives in this report is to provide some guidance on how the dataways can be opened.

2 OVERVIEW OF SPACE SCIENCE DATA

This section broadly characterizes the observational data collected in the three major space science disciplines: planetary sciences, astronomy and astrophysics, and space physics. It reviews the status of long-term data archiving in those disciplines and identifies the major issues associated with that process. In planetary science, most of the data archiving effort is carried out by the Planetary Data System. The procedures used by the Planetary Data System provide perhaps the best model for life-cycle data management and archiving in the space sciences. The Venus data acquired through the recent Magellan mission are described below as one such successful example.

In astronomy and astrophysics, observations are obtained by both ground-based and space-based instruments. Greater emphasis on data archiving has been given for space-based observations, especially in the Hubble Space Telescope project and within the high-energy astrophysics community. The Astrophysics Data System, however, is at an earlier stage of development than the Planetary Data System.

Most archiving of space physics data is done at two centers: the NASA National Space Science Data Center and the NOAA National Geophysical Data Center. A fledging Space Physics Data System has been initiated, but has not yet had sufficient time or resources to significantly influence the archiving efforts in this field.

Planetary Data

Planetary data are acquired by both ground-based and space-based observations. Planetary data include observations of the entire physical system and forces affecting a planet or other body, including the geology and geophysics, atmosphere, rings, and fields. The sensors used collect data across much of the electromagnetic spectrum. Currently, most planetary observations are supported by NASA, either as the direct result of planetary missions or ground-based observations that support a mission. Over the past three decades, NASA has sent robotic spacecraft to every planet in the solar system except Pluto, to two asteroids, and to three comets. Men have walked on the moon, performed experiments there, and returned samples. The knowledge we have about the bodies in the solar system, with the exception of our own planet, is due in large part to space missions. In some cases, such as the gas giants Jupiter, Saturn, Uranus, and Neptune, robotic space probes have provided almost all of our current knowledge. Many of the moons of the other planets were no more than points of light with minimal spectral and light-curve measurements before the Voyager mission. Now each is recognized as a separate world with highly individual characteristics.

The Planetary Data System (PDS) was created by NASA to provide a cost-effective system to preserve the scientific results of past and present planetary exploration missions and to make those data readily accessible to the planetary science research community. The PDS is supported by NASA's Office of Space Science (OSS)1.

1  

Called the Office of Space Science and Applications until March 1993.



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