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Portals to The Universe: The NASA Astronomy Science Centers 1 Introduction The astronomy science centers1 established by NASA to serve as interfaces between astronomy missions and the community of scientists who utilize the data from those missions have been enormously successful in enabling space-based telescopes to achieve their scientific potential. As described below, NASA science centers have transformed the conduct of much of astronomical research and set in place a new paradigm for the use of all large astronomical facilities. It is against this background of success that the committee that wrote this report had been charged by NASA with comparing the approaches taken by the science centers to the requirements they faced, drawing on experience for best practices from their experience, and making recommendations for future science centers. The NASA astronomy science centers perform a number of essential functions for the research community. It is through the centers that most scientists get to use the space-based telescopes. The centers construct the observing programs of the satellite/telescopes. Data gathered by the telescopes pass through the centers to the scientific community via an archive that preserves the data for future research. The centers construct and maintain the software necessary to carry out the preceding functions as well as the vital software for data reduction. They have taken over what was traditionally the NASA Headquarters role—namely, announcing opportunities for proposal submission and conducting proposal review, ranking, and award of observing time. NASA financial support to mission users in the form of data analysis grants typically, though not necessarily, passes through the science centers. The centers also interface with the public and conduct programs in science education and public affairs. 1 In this report, unless noted otherwise, “center” refers to an astronomy science center associated with a NASA astronomy mission, such as the Space Telescope Science Institute (STScI) or the Chandra X-ray Center (CXC), not to a NASA field center, such as NASA’s Goddard Space Flight Center (GSFC) or Marshall Space Flight Center (MSFC). In addition, the committee views astronomy science centers as including stand-alone centers such as the Space Telescope Science Institute as well as archival science centers, such as the Infrared Processing and Analysis Center (IPAC) and the High Energy Astrophysics Science Archive Research Center (HEASARC), which are umbrella institutions for certain mission-oriented science centers.
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Portals to The Universe: The NASA Astronomy Science Centers EXPANDING ACCESS TO SPACE ASTRONOMY DATA The early years of the space program were dominated by entrepreneurs who developed instruments for inclusion in rocket payloads and then on satellites. The data from those experiments belonged to the entrepreneurs, so there was no requirement to invest resources into making the data usable by other researchers. New data formats were invented for each new set of observations, and it was impossible for researchers to use the data without the expert assistance of the primary investigators. Although the data were formally deposited in NASA’s National Space Science Data Center (NSSDC), the archive was effectively inaccessible without an invitation to visit the home institution of the principal investigator (PI). NASA and the astronomy community took several steps to remedy what had become an insular culture for accessing space astronomy data by expanding the number of users and increasing the use of the data. These steps included but were not limited to (1) the introduction of a new institutional model for NASA astronomy science centers, as exemplified by the STScI; (2) informal and formal measures to provide access to archival data from space astronomy missions; (3) NASA requirements to expand use of space astronomy observatories through guest-observer programs; (4) standardization of data formats; and (5) expansion of the role and functions of astronomy science centers to include proposal reviews and education and outreach. An Institutional Arrangement for NASA Astronomy Science Centers A milestone in the emergence of NASA astronomy science centers was reached with the planning in the early 1970s for the Large Space Telescope, renamed the Hubble Space Telescope (HST) after launch. A mission of this scale clearly had to be considered a national if not an international resource, and NASA and the astronomy community were anxious to engage a larger fraction of the community as users of the data. To do this, the Hornig Committee2 was chartered to “undertake a study of the possible institutional arrangements for the use of the ST [Space Telescope].”3 The Hornig Committee report, released in 1976, recommended the creation of an independent, nongovernmental institution for archiving the data and supporting the telescope users. Although the report was meant to be published just in time to provide a scientific management model for the Hubble Space Telescope, the spacecraft was not launched until 14 years later. At the same time, during the late 1970s, NASA had also become aware that a larger community of scientists was eager to participate in the entire enterprise of space astronomy. In response to this growing community interest, mission groups such as the International Ultraviolet Explorer (IUE) and the Einstein Observatory, which were operating at the time, took steps to increase access to the data. The IUE, launched in January 1978 and operated out of the Goddard Space Flight Center (GSFC) and the Vilspa satellite-tracking center in Villafranca, Spain, was essentially an all-guest-investigator facility that was modeled on a typical ground-based mountain observatory. Investigators went to Goddard or Vilspa and gave first-hand instructions to a satellite operator for their observations. They could immediately access first-level processed data to utilize simple analysis programs and to develop their own specialized analysis software. IUE operated in this mode for 18 years, servicing astronomers capable of “going to the mountain” to do their observations and of developing their own software for detailed analysis. In addition, the Einstein Observatory, launched in 1978 as the first true x-ray observatory, represented a revolution- 2 National Research Council, 1976, Institutional Arrangements for the Space Telescope—Report of a Study at Woods Hole, Massachusetts, July 19-30. 3 Ibid., p. iv.
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Portals to The Universe: The NASA Astronomy Science Centers ary increase in x-ray astronomical capability and was an important step forward in the manner in which nonexperts could access data from NASA missions. As in the case of IUE, guests could plan observations, although the preparation of the detailed Einstein observational program required the assistance of specialists. Unlike IUE, which recorded the spectra of individual objects, the Einstein Observatory made x-ray images of the sky. Guests were provided with extensive data analysis support by members of the Einstein team, with the standard scenario involving a weeklong visit to the Einstein Center at the Harvard-Smithsonian Center for Astrophysics in order to learn how to utilize the data and the analysis software. The imaging data lent themselves to large archival survey studies, which were conducted almost exclusively by the members of the Einstein team, who could easily access the data and develop the necessary software. Although the data format was unique to the Einstein mission and the analysis software was not easily exported or externally maintained, the processed Einstein Observatory imaging data were made available for archival research to an extent not previously achieved for astronomical data from space. The availability of archival data expanded the range of users of IUE and Einstein data to include non-x-ray astronomers who sought to augment their understanding of astronomical objects by analyzing x-ray observations of the same objects. Finding: The International Ultraviolet Explorer and Einstein missions demonstrated for the first time that NASA astronomy science centers could expand the number of users of NASA astronomy data, including researchers new to those wavelength bands. By 1980, NASA required that observatory-class space astronomy missions set aside a portion of their observing time for guest investigators during the operations phase of the mission. Further, all investigators were formally obliged to provide documentation to accompany the data deposited in the NSSDC. The documentation would allow archival researchers to use the data without the intervention of the PIs. Although this requirement has always been in place, it has not been consistently enforced until now. For example, in 1983, NASA launched the Infrared Astronomy Satellite (IRAS), which mapped the entire sky in several infrared bands. No guest investigations were included in the mission operations, and no data were released until about a year after the 10-month mission was completed. The initial data processing was carried out entirely by the PI team. In 1986, NASA established the IPAC on the campus of the California Institute of Technology (Caltech) to make the IRAS database available to the astronomy community, and IPAC continues to maintain the IRAS data and to provide access to additional archives and services. Standardized Data Formats During the early 1980s, standardized data formats also contributed to expanding the use of data from space astronomy missions. The advantages of standardized formats became so obvious that in 1982 the International Astronomical Union endorsed the use of the Flexible Imaging Transport System (FITS) by all observatories. (FITS had been developed to handle the interchangeability of images obtained with the telescopes of the National Optical Astronomy Observatories and those of the National Radio Astronomy Observatory.) The NASA-commissioned Astrophysics Data Operations Study of 1986,4 chaired by Franklin Martin, noted that “the standardization of data formats required for analysis is already well advanced; largely through the efforts of National Science Foundation, the FITS format has become a 4 F. Martin, 1986, Astrophysics Data Operations, Greenbelt, Md.: NASA Goddard Space Flight Center.
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Portals to The Universe: The NASA Astronomy Science Centers world standard for astronomical data.” NASA formally endorsed the utilization of FITS and created a FITS standards office at the NSSDC. Nevertheless, space astronomy mission centers continued to develop their own brand of data management and analysis tools outside the FITS environment. The NASA-commissioned Squibb Report5 not only endorsed FITS as the standard format but also suggested the establishment of wavelength-based archival centers to be responsible for the archiving and accessibility of NASA data. The first such assignment, in 1990, was HEASARC at GSFC, for NASA’s x- and gamma-ray data resources. NASA subsequently assigned responsibility for archiving ultraviolet and optical data from space and from digitized ground-based images to the Multimission Archive at the Space Telescope Science Institute (MAST) in 1997 and for infrared and submillimeter data to IPAC in the mid-1990s. Since those original wavelength designations, the centers have become more general and include other wavelength databases in their archives. While the data archived for the long term were required to be stored in multimission FITS format, data in standardized format were not always immediately available to users. For example, data from the German Roentgen satellite (ROSAT; launched in 1990) were processed and analyzed in Germany in their own binary format, reprocessed at GSFC, analyzed with multimission HEASARC-generated software in FITS format, and then reanalyzed in accordance with a third set of protocols under the Post-reduction Offline Software (PROS) developed at the Smithsonian Astrophysical Observatory (SAO) in an effort to be compatible with the Image Reduction and Analysis Facility (IRAF) shell utilized at STScI for Hubble data. In fact, it was not until 1995 that STScI modified its tables software package to directly support FITS tables, and IRAF support for directly reading and writing FITS format data (limited to images, not tables) was not provided until 1997. These processing challenges presented obstacles for users and limited the impact of the data. Guest Observer Data Access and the Internet The two NASA support centers for U.S. users of ROSAT data (at GSFC and the Smithsonian Astrophysical Observatory) provided NASA with experience in the utilization of guest observer facilities (GOFs) during the transitional period, when the Internet was becoming a prime resource for scientific data transmission and analysis. The original plan for ROSAT was that users would first visit SAO to receive some training and experience in analysis software with the help of resident SAO users, who could leverage their very successful experience with the Einstein Observatory. The users could then obtain ROSAT (and other spacecraft) data remotely from Goddard, which they could then analyze from their home institutions. This was a great leap forward in providing service related to non-U.S. missions to U.S. scientists. In earlier missions such as the European X-ray Observatory Satellite and the Japanese Ginga, U.S. scientists had to arrange extensive visits to the home centers of these missions in order to learn how to utilize their data. Soon after the ROSAT data became available, Goddard also made the data from the Japanese Advanced Satellite for Cosmology and Astrophysics (ASCA) x-ray observatory available in the same FITS format and made them amenable to analysis with the multimission tools that were being developed at the HEASARC for ROSAT. As time went on, more and more users preferred to obtain their data remotely without having to visit, sometimes more than once, the mission-specific host facility for training. 5 G.F. Squibb and C. Cheung, 1988, “NASA astrophysics data system study,” in Astronomy from Large Databases: Scientific Objectives and Methodological Approaches, A. Heck and F. Murtagh, eds., European Southern Observatory Proceedings No. 28, pp. 489-496.
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Portals to The Universe: The NASA Astronomy Science Centers EXPANDING THE ROLES AND FUNCTIONS OF SCIENCE CENTERS Proposal Support The science centers all ultimately assumed the management and support of guest observer proposals to NASA and requests for time on their observatories. The idea of centers actually helping users write their proposals evolved gradually. For instance, the user guides for instruments onboard the Einstein Observatory helped proposers understand the capability of the instruments—that is, what could be observed—and was a first step in proposal support services offered by science centers. By 1990 virtually all centers and GOFs provided realistic simulation software for their observers. At that time, STScI also started selecting the proposals, a function that NASA Headquarters had always managed itself. Space astronomy mission centers had always been responsible for the technical evaluation of proposals and their implementation once selected, but NASA Headquarters had always managed the actual proposal collection, the establishment of peer evaluation panels, and final decisions, including funding level. STScI was able to provide all of those functions under general guidelines from NASA Headquarters, and NASA Headquarters asked STScI to handle proposal selection for HST observations, for HST archival data analysis, and for data analysis in MAST. As a result of STScI’s success, virtually all mission-specific proposal reviews are now conducted by the mission science centers. Education and Public Outreach Finally, a function common to all centers is a program of education and public outreach (EPO). NASA mandated an EPO program for the HST and included this activity within the STScI. Part of this EPO program was the dissemination of data and research results beyond the research community to students and interested members of the public (see Chapter 5). The STScI approach to EPO allowed for the integration of research results, supported researchers who could discuss the results in various forums, and enabled EPO specialists to work together to greatly raise the visibility of research results and bring the wonder and excitement of astronomic exploration into the homes of all Americans. Since that mandate, NASA has made EPO an essential feature of all NASA science missions, and by extension an essential feature of the astronomy science center. Finding: The NASA astronomy science centers have transformed the conduct of astronomical research worldwide by allowing remote access to and utilization of NASA astronomy data by researchers, students, and the interested public. In so doing, the centers have been essential to the realization of the scientific potential of NASA astronomy missions. Finding: The Space Telescope Science Institute provided the community with new standards for user support in proposals and data analysis, established a new paradigm for communicating to the public the discoveries of the NASA astronomy program, and set the first example of a program in science education that was an integral part of science center operations.
Representative terms from entire chapter: