NSSDC/WDC-A-R&S 1999-01


Joseph H. King
National Space Science Data Center
Greenbelt, Maryland 20771

Table of Contents








4.1. NSSDC Information Systems

4.2. NASA/Science Office of Standards and Technology (NOST)

4.2.1. Consultative Committee for Space Data Systems (CCSDS)

4.2.2. Flexible Image Transport System (FITS) Technical Panel and Support Office

4.2.3. Common Data Format



Figures 1-4

Appendix - Selected 1998 research papers acknowledging NSSDC

1998 Annual Report of the National Space Science Data Center





The National Space Science Data Center is pleased to issue this 1998 Annual Report describing (1) the 1998 growth and evolution of NSSDC's data archives, access pathways, and other tools and services, and (2) the 1998 access to those data and services by NSSDC's customer communities. This report has been made WWW-accessible in the hope that readers will avail themselves of the opportunity to link to the services reported herein.

The scope of this report is that of the traditional NSSDC as defined by the NSSDC budget. It should be noted that some of the activities thereby supported are the responsibilities of the Astrophysics and Space Physics Data Facilities, organizational peers of the formal NSSDC within Goddard's Space Science Data Operations Office.

I welcome suggestions for user-benefiting improvements to this Annual Report and to NSSDC services.

Joseph H. King
Head, National Space Science Data Center



  2. This report characterizes NSSDC's data holdings, metadata holdings, access pathways, and value-added data products, tools, and services at the end of 1998, with a focus on the 1998 activities leading to that end-of-year state. In addition, this report characterizes the nature and amount of 1998 access to NSSDC's data and services by its multi-component customer community.

  4. The most important result of NSSDC’s 1998 activities is the continuing preservation of growing space science data volumes, ensuring their continuing and future accessibility to the space science, education, and general public communities. The statistics to follow reveal that NSSDC’s archive has now grown to 12.5 TB of space science data, and an additional 3.3 TB of Earth science data, being managed, with the addition of 2.7 TB to this archive in 1998. Approximately 80 GB of these data were moved to new media in 1998.

    Next, NSSDC continues to distribute large amounts of data by network to the space science community and general public, and by offline mailings to the general public. Again, following statistics detail the data volumes disseminated via various pathways to various communities. We note here that during 1998, NSSDC’s customers downloaded via network 1.03 million data files and received about 4 TB of data on mailed media.

    NSSDC’s data dissemination is leading to the publication of significant new science. The Appendix of this Annual Report lists 60 science papers acknowledging NSSDC data or services as contributing to their analyses. These are papers which have come to the attention of our staff; most science journals in which NSSDC-data may have been used are not reviewed by our staff routinely, so the list represent a lower limit on NSSDC-benefitting papers.

    Through its NASA/Science Office of Standards and Technology (NOST), NSSDC provides international leadership in providing increasingly effective digital data archiving. During 1998, the ISO/CCSDS-sponsored Archive Reference Model was exposed for wide review and was presented in various forums where it received strong endorsement. In addition, NOST defined and convened the Digital Archive Directions (DADs) workshop to define the next steps in digital archive definition. These achievements are further discussed in the NOST section of this Annual Report.

    NSSDC was active in the evolution of the distributed NASA/OSS data environment. In addition to participating as a member of the Space Science Data Service (SSDS) Technical Working Group, NSSDC reached agreement with the Multi-Mission Archive at the Space Telescope Science Institute (MAST) active archive for optical/UV data for the MAST to assume data distribution roles and for NSSDC to serve as permanent archive for such data. In keeping with a similar agreement reached with the High Energy Astrophysics Science Archive Research Center at Goddard, NSSDC received the first HEASARC data volumes for permanent archiving. In addition, NSSDC was active in developing, with others of the Sun Earth Connection (SEC) community, recommendations to NASA/OSS for implementation of a SEC Data System (SECDS).

    Emerging from the SSDS and SECDS deliberations is a clear recognition of NSSDC’s dual roles as the permanent archive for data from almost all NASA/OSS missions, and as the active archive (network dissemination, resident expertise, etc.) for data from many missions. NSSDC and many other OSS-supported sites constitute SSDS’s active archive component, each supporting mostly different suites of data.

    As an alternative approach to the centralized, CDF-based OMNIWeb, COHOWeb and CDAWeb systems providing browse and download functionalities to various magnetospheric and heliospheric data sets, NSSDC used JAVA and C to create ATMOWeb as a new retrieve/browse interface to atmospheric and ionospheric data which are held at NSSDC as ASCII tables and which are ftp-accessible from NSSDC. ATMOWeb promotes JAVA applet downloading along with data, such that the user’s computer uses its cycles in plotting data rather than cycles of NSSDC’s computers.

    NSSDC’s OMNI data set, holding virtually only IMP 8 data for the 1980’s and 1990’s until very recently, started to have many of its 1990’s data gaps filled by the addition of time-shifted data from the ISTP/Wind spacecraft. OMNI should eventually be essentially gap-free for the times after the Wind launch in September, 1994.

    The tools supporting both NSSDC and external-community use of the Common Data Format were made much more user effective through a conversion from command-line-based to GUI-based (GUI = Graphics User Interface.)

    A COBE-specific server environment was established to support anon/ftp COBE data access and to host the family of COBE WWW pages. This family of pages was enriched through the creation/addition of DIRBE and FIRAS data browsing tools, a COBE Educational Resources page, and 3-dimensional (VRML) COBE/DIRBE-based models of the interplanetary dust cloud and the Milky Way star distribution.

    At the request of the NASA Chief Information Officer, NSSDC played a central role in the development of a white paper on NASA science data retention. This paper will underlie a new Science Data Retention policy statement, which will, among other things, govern the relation between NASA and the National Archives and Records Administration (NARA) regarding what data come to be permanently archived at NARA. This is an area that had become somewhat confused.

    NSSDC brought many datasets to network accessibility for the first time in 1998. Particularly noteworthy was an effort whereby several IBM/binary (1973-1991 data) and VMS/binary (post-1991 data) NSSDC-archived tapes, holding 11-min resolution energetic particle rate data from the U. Maryland experiment on IMP 8, were read, and ASCII records were created containing a subset of words from the original binary records. These data were then made network-accessible from NSSDC/NDADS. Occasional interactions with the original U. Maryland team occurred during this effort.

    Among the items made network accessible from NSSDC during 1998 were: the current Guideline for Developing a Project Data Management Plan; a page listing and characterizing the 70+ Explorer spacecraft launched by NASA since the late 1950’s; an index page guiding users to NSSDC’s various WWW-accessible interfaces through which data from various SEC missions are available.

    A great deal of effort was expended on ensuring that NSSDC systems would run correctly in the year 2000. NSSDC’s general software environment was brought under much improved configuration management for this. Only minor renovations of NSSDC’s applications software were needed. One significant problem came up relative to NSSDC’s ability to continue creating new WORM optical platters for NDADS in the new millenium, but NSSDC anticipates having no further need for this as the NDADS optical disk jukeboxes, now approaching 10 years old, are expected to be supplemented in 1999 by new systems to which all new-data-writing will be done.

    NSSDC’s WWW home page received a new columnized look-and-feel. User access to this page and to the many pages in the NSSDC tree of WWW pages continues to grow, as detailed later in this Report.

    Readers are encouraged to exercise the multiple options on the hierarchical array of WWW pages starting with NSSDC's home page. There are several more functionalities beyond those called out in the preceding paragraphs.



    There are several ways to characterize the multi-disciplinary NSSDC archive. Byte counts are a common metric for modern archives, and will be reported herein. Numbers and diversity of media volumes managed, and numbers of distinct data sets, are also very important. (In NSSDC's terminology, a data set is typically all the data from a given instrument at a given processing level in a given format.) The diversity of data sets and of media types relate to the intellectual heterogeneity and technical heterogeneity of the archive, respectively, and we shall report on these also.

    At the end of 1998, NSSDC had 4,435 distinct data sets and accompanying documentation packages being managed. Table 1 indicates the disciplines from which these data sets come, and a breakout as to whether the data sets are digital or non-digital (film, etc.). The table shows that these data sets come from 1,346 experiments which have flown on 395 mostly-NASA spacecraft. By data set count, space physics is the dominant discipline, accounting for over half NSSDC's data sets. This reflects the fact that in its early years, NASA launched a preponderance of multi-experiment space physics missions and also that space physics spacecraft typically carry more independent experiments than do astrophysics missions.

    Note from the table that NSSDC manages roughly equal numbers of digital and non-digital (mostly film) data sets, although it should also be noted that NSSDC has been acquiring almost no non-digital data in recent years.

    Table 2 is a different characterization of the NSSDC archive, by byte counts and media volume counts. The table shows 15.8 TB of total data, a 2.7 TB subset which is network-accessible, and 70,271 digital media at NSSDC. The byte counts are estimates, involving for some data sets assumptions about the mean numbers of bytes on various media types.

    Note that only astrophysics data and space physics data are network-accessible from NSSDC. That planetary data are not network-accessible is the result of the emphasis of the Planetary Data System (through which virtually all planetary mission data has entered the NSSDC archive for the past several years) on CD-ROM production and dissemination, and because PDS nodes are now making the most important planetary data network-accessible from their nodes. [Exceptions are NSSDC's photo gallery and image catalog which are WWW-accessible from http://nssdc.gsfc.nasa.gov/planetary/; these are largely oriented towards the general public.] NSSDC's Earth science data are gradually being migrated to the EOSDIS data management infrastructure, hence are not good candidates for network-accessibility from NSSDC.

    Tables 3a and 3b better characterize NSSDC's network-accessible astrophysics and space physics data, by project and by whether the data are immediately accessible from magnetic disk (online) or from the robotics-based NDADS system (nearline). Data held online are typically of relatively small volume and high interest, although falling prices for magnetic disk is facilitating the expansion of NSSDC’s online data stores. Figure 1 shows the growth of the nearline data volume over the past five years, and indicates which projects' data ingest started in which years. It should be noted that NDADS reached ingest rates in the 80 GB/month range in the second half of 1997, but declined in 1998 as the conclusion of the IUE Final Archiving effort was reached.

    Figure 2 characterizes the data volumes made network accessible via NDADS during 1998. Most of these data first arrived at NSSDC during this year, while a small amount was promoted to network accessibility from NSSDC's offline archive. Data inflow to NSSDC during 1998 is discussed in more detail subsequently.

    Table 4 characterizes the digital media managed at NSSDC, not including back up copies. This table is an expansion of Table 2 in which total numbers of unique digital media volumes were given. It should be noted that most volumes are replicable and have one backup volume. However, for "CD-ROM (Titles)" which are not locally replicable, NSSDC typically holds between 20 and 200 copies of each title. For these, NSSDC must replenish stock through a commercial vendor as request activity drives NSSDC stock down. Note also that DLT (Digital Linear Tape) appears for the first time

    Table 5 identifies NSSDC's cumulative non-digital archive, by disciplines by form factor. Note that NSSDC has large volumes of non-digital data for each of the discipline areas it supports. It should be noted, however, that very little new data are arriving at NSSDC in non-digital form in recent years.


    2. Tables 6 and 7 characterize the inflow of digital data to NSSDC during 1998. In particular, Table 6 shows that NSSDC received approximately 2.7 TB of new data in 1998, via a combination of networks and hard media. This is approximately 30% more than in 1997. Table 6 shows data volumes by project, with the astrophysics (gamma rays) and space physics subsets of ISTP/Wind data attributed to their respective disciplines. Note the dominance of EUVE, IUE, FAST and ISTP missions. Table 7 characterizes the inflowing media types by discipline. CD-WO media are the dominant input media type overall.

      During 1998, NSSDC received approximately 280 GB of data electronically, in addition to the data arriving on the media reported in Table 7. The electronic inflow was dominated by the ISIS ionogram digitization effort (135 GB), with lesser amounts from a number of spaceflight projects. See Figure 2 for details.

      By data set count, which as noted earlier marks the intellectual heterogeneity of NSSDC, increments or totalities of 84 distinct data sets arrived at NSSDC during 1998. Of these 84 experiments, first data were received from 16 experiments, four on FAST, two each on Clementine, EUVE, and Ulysses, and one each on CRRES, Geotail, Hinotori, Mars Observer, Mars Pathfinder, and STP S81-1 (DOD).



    NSSDC provides user access to its data holdings through multiple electronic interfaces and, in addition, through a user support infrastructure for the mailing of offline digital and non-digital data volumes. Most electronic interfaces are accessible through NSSDC's WWW home page and include: (1) special WWW-based interfaces to specific data sets or groups thereof; (2) anonymous/FTP pathways to a range of data files maintained permanently on NSSDC magnetic disk as well as files staged from NSSDC's nearline mass storage environment; (3) WWW-based and other interfaces to that nearline environment for the purpose of selecting data files and having them staged or downloaded.

    The dominant special WWW-based data access interfaces NSSDC offers relate to ISTP key parameter and selected other space physics data (CDAWeb), the OMNI and uniformized-COHO solar wind datasets (through OMNIWeb and COHOWeb, respectively), IRAS, COBE, and the Astronomical Data Center astronomical source catalogs and journal tables.

    The OMNI data set is a 35+ year compilation of multi-spacecraft near-earth solar wind magnetic field and plasma data and energetic particle data, while the COHOWeb database is a uniformized set of files of merged magnetic field, plasma, and position data for each of many deep space spacecraft. Table 8 shows annual statistics for the CDAWeb, OMNIWeb, and COHOWeb systems. Note the continuing strong growth in CDAWeb usage (200+ user-created plots, lists, or files daily in 1998), the slowing growth in OMNIWeb usage (30+ such items daily), and the plateau in COHOWeb usage (5 such items daily). These are all major community assets.

    In the Astronomical Data Center, 2600 astronomical source catalogs and journal tables are maintained online for easy access. Entire catalogs and tables can be retrieved via FTP. New WWW based tools are available for browsing, plotting, and subsetting the contents of the catalogs and tables before download. To enable interoperability with other data facilities, a programmer's interface has been developed to allow external software to directly access the ADC catalogs without going through the Web browser. During 1998, the system experienced approximately 30,000 accesses per month. This was nearly double the access rate of the previous year.

    A great many NSSDC data sets and other information services are held permanently on magnetic disk for Anonymous/FTP access from NSSDC’s VMS and UNIX computers. The reader is invited to review all these services from the FTP link on NSSDC home page. Table 9 gives the annual counts of files downloaded from the combination of these computers, both overall (665,000 files in 1998) and for the directories with the most activity. Note that these include public interest options (Photo Gallery), standard formats information and tools (CDF, FITS), "real" data (COHO), and geophysical model information, coefficients, and software. These counts do not include data files FTP-downloaded after having been staged from NSSDC’s NDADS nearline system; relevant statistics on NDADS access are discussed in the following paragraphs.

    Table 10 summarizes the 1998 accesses to NSSDC's nearline mass storage environment (NDADS) through the multiplicity of available interfaces. Note that three measures are offered for each mission supported. A request is the specification of one or multiple "entry ID's" each of which specifies one or more data files. Both request counts and counts of files are reported. Finally as a measure of the breadth of interest in the data from any given mission, we count on a monthly basis, and report annual means of these monthly counts, the numbers of unique electronic addresses (username @ site) accessing each mission's data.

    NDADS hosted a totality of 9,466 requests in 1998, for a total of 0.37 million data files. IUE data and the IUE user community continued to be the dominant beneficiary of NSSDC's nearline environment in 1998. Other broadly based communities accessed data from IMP 8, ISTP, and IRAS.

    WWW access statistics are frequently misleading, insofar as they usually individually count the many files (buttons, etc.) that make up a page. Nevertheless, growth in WWW accesses is indicative of continuing and growing use of the WWW-provided services. Figure 3 shows the raw numbers of WWW hits from NSSDC’s two main www servers, nssdc and bolero. In 1998, there were 7.5 million hits monthly! The 1997 peak was due to the great public interest in the July, 1997, excursion of the Mars Pathfinder mission’s Sojourner rover on the martian surface; this event did not have a counterpart in 1998.

    While the dominant mode of dissemination of data to the astrophysics and space physics research communities is via the internet, NSSDC continues to provide a high level of offline data dissemination. The customer community for this offline data dissemination is to a large extent the general public, including educators and students. Table 11 characterizes this user community of NSSDC's offline data services.

    Table 12 gives the counts of requests for offline data sets from various disciplines in 1998, and as integrated over NSSDC's history. (A small fraction of requests which are multi-disciplinary are double counted in this table.) Note particularly the dominance of planetary data over both time scales. This is largely associated with lunar and planetary image data which are widely requested by the general public. The high level of astrophysical offline activity reflects requests by the amateur and professional astronomical communities for ADC catalogs on CD-ROM.

    Table 13 shows the most recent 5-year history of NSSDC's offline data request activity by media type. Several points are noteworthy. The dominant mode of offline digital data dissemination is now via CD-ROM. It is of interest to note that every working day of 1998, NSSDC mailed about 27 CD-ROMs to 4 requesters.

    Also significant from Table 13 is the fact that requests to NSSDC for film data have not declined over the past 5 years and in fact were up significantly in 1998. NSSDC finished more than one film request every working day.

    Finally, very noteworthy is the distribution of about 3950 copies of the Multi-wavelength Milky Way poster created in 1996 by the SSDOO/Astrophysics Data Facility as a special education/outreach product. These distributions are not included in the counts of Tables 11 and 12.


    In addition to its archive of scientific data characterized in the preceding part of this Annual Report, NSSDC offers a number of additional services which are described in this Section.

    1. NSSDC Information Systems

    2. The Automated Internal Management (AIM) database identifies virtually all launched spacecraft, the experiments carried by many of those spacecraft, and data sets primarily as archived at NSSDC. Table 14 identifies the numbers of spacecraft, experiments, and data sets described in the AIM File, along with the numbers of new entries made in 1998. The database serves as the source of information for many of NSSDC's WWW information pages. The NSSDC Master Catalog (NMC) and a number of discipline project pages retrieve information from AIM and build WWW pages "on the fly" so that the latest information is presented to the user. Figure 4 shows the continuing rapid growth in WWW-based access to AIM/NMC descriptions over the 1995-1998 interval, with over 95,000 accesses in 1998 and a near doubling of the access rate in each of the past three years.

      The AIM database also serves as a useful source of comparative information about spacecraft, experiments, etc. such as launch dates, time spans of data, orbital characteristics, time resolution, data availability, etc. The presence of comparative information in a consistent format within a single database makes the database especially valuable for survey reports.

      The NSSDC Supplementary Data File (NSDF) is similar to AIM, but slightly different from it. It tracks non-spacecraft data, multi-source spacecraft or other data, models and programs, and other NSSDC-held data sets that do not fit the AIM spacecraft/experiment/data set hierarchy. See Table 15 for NSDF statistics.

      The Technical Reference File (TRF) tracks individual published and unpublished papers associated with space flight experiments. The NSSDC ID for the experiment is attached to the reference information so lists of papers relevant to a particular experiment can be reported, and/or provided to persons accessing data from a given experiment from NSSDC. TRF also contains references to selected standards relevant to space science data management as well. TRF statistics are given in Table 16. The TRF was used to generate the Appendix.

      The Interactive Request and Name Directory (IRAND) tracks people who have interacted with NSSDC over the years. It includes full names, one or more addresses, telephone and email information, and what NSSDC distribution lists they are on. The database contains approximately 55,000 entries. This information is also accessed and made available through the PIMS interface on the NSSDC WWW Home Page. Further IRAND statistics are available as Table 17. Note especially that over 10% of the records were updated in 1998, reflecting volatility of such information items as Internet addresses. IRAND also tracks individual staff-involved requests, almost 80,000 over the years.

      The Interactive Data Archive (IDA) is another database of interest. IDA tracks the inventory of NSSDC's digital data volumes (tapes, disks, etc.). IDA had 158,805 records at the end of 1997, with 2,559 records having been added during 1998.


    3. NASA/Science Office of Standards and Technology (NOST)

    4. NOST's mission is to facilitate the recognition and use of standards to reduce cost/benefit ratios in the exchange and management of scientific data among NASA entities and the scientific communities they serve. NOST's Web Home Page is at http://ssdoo.gsfc.nasa.gov/nost/.

      The NOST strategy is to play a coordinating role in helping the science disciplines identify new standards requirements. NOST participates in partnerships with them, other agencies, and industry on facilitating the adoption of leading-edge technologies with national or international visibility that can be tailored to meet NASA science information management and exchange requirements, and it assists in the process of moving these technologies toward standards with commercial support.


      1. Consultative Committee for Space Data Systems (CCSDS)

      2. NOST operated NASA's highest level Control Authority office in accordance with the applicable Consultative Committee for Space Data Systems (CCSDS) and ISO standards to formally archive data descriptions for interchange and long term preservation. Forty-three (43) new descriptions were registered, and 333 descriptions were under maintenance as of December 31, 1998. The primary missions supported were: ACE, Canopus, Geotail, Greenland Magnetometer (ISTP-related), Interball-Aurora, Interball-Tail, and Polar.

        NOST participated in the development of draft CCSDS/ISO standards applicable to multi-discipline and sub-discipline information interchange. The primary standards and their usage categories were:

        Data Entity Dictionary Specification Language (DEDSL): This draft standard, which was out for formal review by the agencies, has been revised in response to comments on a need to harmonize it with the conceptual data element standard from ISO known as ISO 11179 and the ANSI X3.L8 standard known as X3.285. This has been done and received favorable review by an L8 member. The DEDSL draft has also been split into two documents - one addressing the conceptual model and one addressing an interchange form using ISO Parameter Value Language (PVL/ODL). This will allow a follow on interchange standard using XML. Liaison activities with X3.L8 continue for updating ISO 11179 and an XML interchange form. This should support publication and exchange of data elements leading to more automated access and understanding of data across science disciplines and among organizations.

        Reference Model for an Open Archival Information System (OAIS): The reference model draft (White Book version 3) was used as the basis for organizing the Digital Archive Directions (DADs) workshop and was strongly endorsed by this diverse collection of participants. Some additions were recommended and therefore the model is being updated. The model establishes initial criteria for recognition of a true archival function and should lead to improved archival implementations,

        provide a basis for further standardization, and provide more cost- effective vendor support. It is now expected to reach formal review in mid-1999.

        Digital Archive Directions (DADs) Workshop: NOST organized and lead the DADs workshop, held at the National Archives, to further expose the OAIS Reference Model and to identify next steps desired for archive recommendations and standards. Attended by participants from a wide variety of government, academia, and industry organizations, including some from the United Kingdom, state of the art efforts in various archival domains and desires for best practices and new standards were identified. Particularly noteworthy were the plenary recommendations for developing some type of archive accreditation methods and the formation of an international archive consortium to promote solutions to common archival needs. A DADs Report is available.

        NOST provides access to various software tools in support of selected CCSDS/ISO standards. These include:

- Parsers for Standard Formatted Data Units (SFDU) Structures

1. SFDU Workbench
2. SFDU Toolkit

        - Parsers for the Parameter Value Language (PVL)

        1. PVL Statement Parser
        2. PVL Toolkit

NOST also facilitates access to software available from other agencies. These include:

        - Software for registering, archiving, and disseminating data descriptions from CCSDS Control Authority Offices

        1. Portable Control Authority Office System

        - Tools for using the Enhanced ADA Subset (EAST) description language

        1. OASIS
        2. EAST Interpreter
        3. EAST Generator
        4. EAST Reformatte
        5. EAST ASCII Dump
        6. EAST Viewer


      1. Flexible Image Transport System (FITS) Technical Panel and Support Office

      2. The Flexible Image Transport System (FITS) is the standard format for astronomical data interchange, endorsed and supervised by the International Astronomical Union (IAU). NOST participates in the evolution of FITS by commenting on proposed new FITS extensions and conventions and by the development of a formal FITS specification document using the NOST standards accreditation process. The FITS Support Office (FSO) of NSSDC/ADF supports the NOST-convened FITS Technical Panel (including Goddard and extra-Goddard FITS experts) in its work and supports the community by providing a number of services, such as current versions of all documents and WWW information pages.

        The FITS Technical Panel completed text for a Draft Standard version 2 of the "Definition of the Flexible Image Transport System." The version of the standard incorporates the image and binary table extensions and the blocking agreement endorsed by the IAU FITS Working Group. The Draft Standard was distributed to the public for review (in LateX, postscript, and html) as part of the NOST certification process. The review period closed in mid-July. The Technical Panel has completed its review and response to the comments and has edited the Draft Standard accordingly. The comments, responses, and final Draft will be posted on our web site shortly, and the FSO will guide the final Draft through the NOST certification. It will then be forwarded to the IAU for ratification. The FSO will support in like manner the development of the new draft World Coordinate System (WCS) now under review by the community.

        During 1998 the community accessed the WWW home page of the FITS Support Office over 28,000 times, a very substantial increase over last year. Networked retrievals of the current Standard, the User's Guide, and the draft Standard were 1260, 1053, and 293 respectively.

      3. Common Data Format

      4. The NSSDC Common Data Format (CDF) is a self-describing data abstraction for the storage and manipulation of multidimensional data in a discipline-independent fashion. CDF is comprised of three parts, the CDF data files that contain both the actual data values and metadata, the CDF software library that is used to create, access, manage, manipulate, etc. CDF files, and a well-defined Applications Programming Interface (known as the CDF Interface) that provides transparent access to underlying software and data. CDF provides the essential framework for which generic applications (e.g., visualization, statistical) can easily be created.

The International Solar Terrestrial Physics (ISTP) Project is NASA's single largest user of CDF. The ISTP Project is using CDF to store its Key Parameter data. The NASA IMAGE mission, to be launched in 2000, will use CDF extensively. In addition, CDF is used heavily by the international community through the IACG projects associated with the ISTP project. This effort provides a consistency among data formats and structures and allows data to be shared transparently among a variety of projects and applications.

A World Wide Web (WWW) page located at http://nssdc.gsfc.nasa.gov/cdf/ on the internet provides a description of CDF, access to the software distribution, documentation, papers, a list of Frequently Asked Questions, and facilitates interaction with the CDF support group at the NSSDC.

During 1998, the tools supporting both NSSDC and external-community use of the Common Data Format were made much more user effective through a conversion from command-line-based to GUI-based (GUI = Graphics User Interface.)

Approximately 10,800 files were FTP-downloaded from the CDF directory of NSSDC’s anonymous account during 1998. These were mostly files describing CDF, software tools from the CDF library, etc. In addition, a great many users browse the CDF pages identified above.


Nathan L. James, nate.james@gsfc.nasa.gov, +1-301-286-9789
Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, USA

NASA Official: Dr. Joseph H. King, Head, NSSDC
Version 1.0, March 1999
Last Updated: March 12, 1999, NLJ