Towards a National Virtual Observatory
Alexander Szalay, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore

Paradigm Shift Coming

Astronomy will experience a major paradigm shift in the next few years, driven by large, systematic sky surveys at multiple wavelengths. We believe that these digital archives will soon be the astronomical community's main avenue for accessing data. Systematic exploration and discovery in these databases will play a central role in the day-to-day research activities of most astronomers. This Data Avalanche --- the flood of Terabytes of data --- is happening, whether we like it or not! The first mega-surveys, like 2MASS, SDSS, and MACHO, are already in progress.

This transition is driven by advances in technology. The last decade has witnessed a thousand-fold increase in computer speed, a significant increase in detector size and performance, a dramatic decrease in the cost of computing and data storage capabilities, and widespread access to high-speed networks. Despite these advances, the environment to exploit these huge data sets does not exist today. In order to efficiently handle Terabytes of data, one needs database engines with fast I/O speeds and advanced query engines, that can access databases spread throughout the country. Existing analysis tools do not scale to Terabyte datasets. These combined factors make a new initiative, the National Virtual Observatory (NVO) both feasible and compelling.

New Astronomy

The NVO will help the astronomer preparing for the next observing run, the theorist analyzing large-scale structure, or the phenomenologist searching for extremely rare objects. The NVO will link the major astronomical data assets into an integrated, but virtual system, to allow automated multi-wavelength search and discovery among all known catalogued astronomical objects. The NVO will initially provide access to tens of Terabytes of catalog and image data, growing to multiple Petabytes by the end of the decade. The NVO will provide a powerful and novel data analysis and exploration environment for the astronomical community, and will enable a qualitatively new and different type of astronomical research: multi-wavelength exploration and discovery over the entire sky using all known catalogued astronomical objects simultaneously. The NVO will influence all disciplines of astronomy and astrophysics, from X-rays to optical/IR through the radio wavelengths, and it will be essential for confronting theories with observations. The discovery process will be accelerated through the application of advanced visualization, data mining, and statistical tools.

The Components

The NVO is National, because it serves the needs on a national scale; it is Virtual, since it supports observations on digital representations of the sky, and it is an Observatory, since it is a general-purpose observational facility, just like a traditional observatory.

The major elements of the NVO include

(i) integration of major data archives;
(ii) advanced services for the astronomical community;
(iii) standards and tool development;
(iv) education.

The NVO will involve a coordinated---but distributed---effort of universities and national centers to develop an integrated data architecture for astronomical research. Such standards and coordination will play a key role in linking the multiple archives and service providers; without them, astronomy will be unable to exploit its data fully and efficiently.

The NVO will be a powerful resource for public education and outreach at many levels. A digital representation of the sky easily accessible via the web has the potential to excite the imagination of future scientists and allow them to participate in the astronomical discovery process. Educators will draw on the NVO to develop educational materials, and public institutions such as planetariums will use the NVO to develop presentations and displays.

The software and standards developed as the core of the NVO will be relevant to other fields of research, and should attract the attention of researchers in computer science, statistics, bio-informatics, earth sciences, and other fields. NVO developers will participate in exchanges with their counterparts working in bio-informatics and earth/planetary sciences. The NVO supports many of the goals of the recent IT2 federal initiative, and is particularly appropriate for multi-agency funding. International collaborations will be an essential component.