1.  Introduction

In the fall of 1997 the leads of the major NASA astrophysics data centers were charged by Guenter Riegler and Joe Bredekamp of NASA HQ with developing a plan for the long term support of the EUVE mission archive which would demonstrate a high level of interoperability among the astrophysics data services and would serve as a pathfinder for improving the interoperability of data services for all of space science. Such integrated data services would allow users to easily search, locate, and retrieve data of interest regardless of where the data are physically stored. The EUVE mission data serves as an ideal test case in that it serves a continuum of science interests that span several disciplines within the space science community (astrophysics, planetary atmospheres, etc.).

Specifically, we were challenged to achieve the following goals:

Statement of Work:

The representatives of the five principal astrophysics archive centers, in close collaboration with the EUVE Science Center (Roger Malina) develop a coordinated and consensus plan and schedule for making EUVE archive data products accessible in compatible fashion across the variety of user entry points and interfaces, independent of the particular physical placement of the archive. This five-way coordination should come up with features (e.g., cross-archive search capability) to be incorporated into the archive infrastructure, and when, with specific applicability to the EUVE datasets. Further functionality leading toward integrated access and presentation should be discussed, along with corresponding priorities and target dates.

Scope:

Items which should be searchable and retrievable for any mission dataset in any of the five centers through any of the center-specific user front ends are:

• Catalog listings (object name, coordinates, major parameters like classifications, brightness/standard flux units, etc.)
• Images (``postage stamps'')
• Spectra
• Tabular data

In response to these challenges several coordination and planning meetings were held in November and December 1997. Two meetings focussed specifically on the EUVE archive and one was broader in scope, dealing with archive interoperability issues in general. The results of these meetings, both in terms of technical infrastructure, user interfaces, and management plans, are presented in this report.

2.  Astrophysics Data Centers Executive Council

A December 17, 1997 meeting at Goddard Space Flight Center was the first to bring together the leads of all of the astrophysics data centers to discuss explicit plans for improving the integration and interoperability of their respective data services. Detailed minutes of this minute are available elsewhere, however the major actions from this meeting include:

• The formation of the Astrophysics Data Centers Executive Council, comprising the leads and key scientific and technical staff of the various NASA-sponsored astrophysics data centers, which will meet quarterly to plan and verify the integration and interoperability of their data services. The primary organizations involved in the ADEC are the NSSDC, HEASARC, IPAC, STScI, and SAO/ASC.
• The primary new service we need to implement is one that enables easy cross-archival searches for data of interest to the user. We will complete the development of the AstroBrowse prototype in order to provide this fundamental search and discovery mechanism. AstroBrowse will enable scientists entering the data systems through any of the existing access points to locate data of interest, independent of where that data is physically stored.
• Several user interfaces will be developed for AstroBrowse in order to demonstrate the flexibility of the approach. A splinter group is coordinating the technical developments of AstroBrowse (Hanisch and Kimball, STScI; McGlynn, HEASARC; and McGrath, Plante, and Futrelle, NCSA), including a full specification of the query profile and incorporation of the CDS ``GLU'' system for maintaining a distributed database of archive and catalog metadata.
• The AstroBrowse system will be enhanced in the longer term to provide some level of standard delivery of data products, and integration of those data products for the user. These facilities will need careful design and development in order to avoid imposing excessive requirements on data providers to modify their internal systems.
• Astrophysics data services must function in concert with the Space Science Data System. As the AstroBrowse data locator tool is developed further, we will work with the PDS and SPDS communities to help generalize it's use to these other disciplines. We will arrange a joint meeting with representatives of PDS in the spring of 1998 in order to start work on astrophysics/planetary science interoperability issues.
• We will work with the ground-based astronomy community and other information services (e.g., catalog services, on-line journals) to enable better integration of all astrophysics resources.

3.  EUVE Archive

Two meetings and several telecons were held in November and December 1997 to develop a plan for providing long term support for the EUVE mission archive. The EUVE data span the technical and scientific interests and expertise of two of the major data centers: HEASARC and STScI. As a UV mission many of EUVE's scientific programs are closely related to IUE, HST, and FUSE programs, and researchers familiar with optical/UV missions will expect access to these data from the STScI archive environment. EUVE can also rightly be called a very soft X-ray mission, and its data formats are identical to those from other high energy missions (time-tagged photon event lists). There is an overlap in the science programs of EUVE and the science programs based on the lower energy detectors on the AXAF mission. Thus, the HEASARC is also a natural point of entry into the EUVE archive.

We have agreed that both STScI and HEASARC will function as primary entry points to the EUVE archive. Having been funded already to provide multi-mission archival support, the HEASARC has portions of the EUVE data already available. Initially both the STScI and HEASARC search and retrieval functions will direct users to the HEASARC copy of the data (which is available via public FTP). STScI will ingest the final science data products into its archive (the total data volume is under 100 GB) if the load on the HEASARC copy of the data proves to be excessive. STScI and HEASARC will work out filenaming conventions that are acceptable to both organizations.

A catalog of EUVE final archive products will need to be generated from the as-delivered FITS files. HEASARC staff will begin work on extracting the relevant header information into an observation catalog, and this catalog will be available at both STScI and HEASARC for search and retrieval purposes. Both STScI and HEASARC plan to support access to other EUVE data products, such as the all-sky survey and spectral atlas, which are quite modest in size. The EUVE catalog will also be made available from within the ADF's catalog viewer tools.

HEASARC also agreed to review the preview images and spectra and, if necessary, to regenerate the previews to be consistent with the final archive data (the previews created at CEA several years ago were based on earlier versions of the data and do not correspond on a one-to-one basis with the data sets in the final archive).

The NSSDC will store all EUVE telemetry data. The EUVE project does not have portable software for re-extracting science data from the telemetry stream, thus it is expected that the telemetry data will not be of much direct utility to any except the most dedicated end-users. The telemetry processing software (the ESW package) will be archived at NSSDC but not actively supported. (EUVE Project personnel estimate that as much as six staff-months of effort would be required in order to modify the ESW software to be operable independent of the specific computing environment that was available at the CEA.) Requests for telemetry data received by HEASARC or STScI will be forwarded to NSSDC, as will any requests for large amounts of data. Requests for individual data sets will be handled directly by HEASARC and STScI using the export media available at those centers.

STScI will support and provide access to the EUVE data analysis software, the EUV package, which is an IRAF layered package. Support and access will commence after the CEA has completed and tested the modifications to EGOCS to make it compatible with the new release of IRAF, Version 2.11. STScI uses the IRAF system extensively, as this is the basis for the HST calibration and analysis software tools. Future support will consist of assuring the operability of the EUVE software against subsequent releases of IRAF and providing easy access to the software for user downloading and installation.