Paper - RSSD - ESA

Astronomical Data Analysis Software and Systems XVI
ASP Conference Series, Vol. 376, 2007
R. A. Shaw, F. Hill and D. J. Bell, eds.
ESA Science Archives
C. Arviset, I. Barbarisi, G. Bini, J. Dowson, N. Fajersztejn, M. Freschi,
P. Gomez, M. Guainazzi, I. Leon, I. Ortiz, E. Parrilla, P. Osuna,
J. Salgado, A. Stebe
European Space Astronomy Centre, ESA, Villafranca del Castillo,
Madrid, Spain
Abstract. The European Space Astronomy Centre (ESAC) will host all
ESA astronomy (except HST) and planetary mission archives, which currently
includes ISO, XMM-Newton, Integral, and the ESA’s Planetary missions archives
(Rosetta, Mars Express, Smart-1, Huygens and Giotto for the time being). In
the future, Herschel, Planck, Soho and Gaia will also have their archives located
at ESAC. In 2002 a dedicated Science Archives Team was created at ESAC. This
team provides support to various archive projects. Each member of the group
is not dedicated to one project in particular, but works on a specific sub-system
across all the archive projects. There are some Database engineers, some experts
on User Interface and the Middle-Tier layer, and others on Data Storage, Data
Distribution and Interoperability. As part of the development of activities at
ESAC, specific budget has now been setup to allow increased VO involvement
of the ESAC Science Archives Team (see Barbarisi et al. 2007).
1. Scientific Archives Development Approach
All Scientific Archives at ESAC are based on a 3-tier client/server architecture
using Java Object Oriented approach and XML, separating the data from the
presentation, which allows a more modular and flexible development. The main
advantages of this approach are the following:
• Java and XML for re-usability: In conjunction with the multi-platform
capability of Java, the use of configurable XML files allows the same code
to be used for various archives.
• Same Look & Feel for ESA Science Archives: Archives are powerful
and easier to use for advanced or frequent users, in that the user immediately
recognizes an ESA archive, which leads to a clear image of ESA
within the scientific community.
• Use of standard protocols: The archives are available on-line or can
be downloaded as stand-alone applications; data distribution is done using
the FTP protocol.
• Easier and cheaper maintenance of existing systems: Re-using the
same architecture from previous projects brings the advantage that less
effort is required to design new projects, and ensures that the architecture
is robust since it has been implemented and used successfully already.
• Knowledge transfer between projects: Each member of the team is
not dedicated to one project in particular, but is working on a specific
sub-system across all the archive projects.
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Figure 1.
ESA Science Archives architecture.
From the beginning, and thanks to their open architecture (see Figure
1), the Science Archives have allowed extensive interoperability with external
archives or applications:
• Access to SIMBAD or NED for target name translation into coordinates
• Access to ADS (Astrophysics Data System) (for IDA and XSA) to link to
electronic articles
• Access to the IRAS archive (for IDA only) to access other Infrared data
• Access to VOSpec, ds9, and Aladin tools for product display
Furthermore, a specific system has been developed to access directly the metadata
and data products without the need to go through the standard user interface.
The Archive Inter-Operability (AIO) system allows remote archives or
applications to access these data via scripts (URLs, socket mode) in an easy and
powerful way.
In the last few years the concept of the Virtual Observatory (VO) has
been embraced by the astronomical community, and the International Virtual
Observatory Alliance (IVOA) has been created. Thanks to their modularity, it
has been easy to add an extra VO layer to the Archives to make them VOcompliant
(e.g., with SIAP, SSA, and SkyNode).
2. Existing Archives at ESAC
The ISO Data Archive 1 (IDA) has been open to the community since 1998 December,
and offers a state-of-the-art archive facility to access ISO data products
1 http://iso.esac.esa.int/ida

ESA Science Archives 705
and auxiliary files. It contains all the ISO raw and fully processed science and
calibration data, highly processed data products, as well as all ancillary data
(engineering, uplink, and downlink data) for a total of about 400 GB stored on
magnetic disks. Through a powerful and user friendly Java user interface, over
1200 registered users have already downloaded the archive content more than
eight times since it was opened to the public.
The XMM-Newton Science Archive 2 (XSA) has been available to the scientific
community since mid-April 2002. It contains all the XMM-Newton raw and
fully processed science and calibration data, as well as some ancillary data, for
an expected total of about 2 TB stored on magnetic disks. It also contains the
second version of the XMM-Newton Source Catalogue, with powerful search criteria.
Based on the IDA architecture and code, it offers similar data query and
retrieval facilities through a friendly User Interface (see Figure 2). Proprietary
data is accessible only to the observation owner, while public data has unrestricted
access. Furthermore, the XSA offers an on-the-fly reprocessing facility
to allow the users to retrieve data that are calibrated with the latest version of
the pipeline processing software.
Beside the Integral archive, located at Integral Science Data Centre in
Geneva, ESA decided to have its own Integral SOC Science Data Archive 3
(ISDA) at ESAC; it is based on the XSA architecture, design, and code. The
first release for ISDA internal use was made in 2003 December, and the public
release took place in 2005 July. The ISDA offers access to all raw and fully
processed data via a powerful user interface, which allows users to browse the
observations, exposures, and science windows catalogs, and to retrieve products
via FTP at all processing levels. The ISDA also respects proprietary data like
the XSA, i.e., full access to public data, and access to proprietary data only by
observation owners and privileged users.
The Planetary Science Archive 4 (PSA: see Arviset et al. 2007) is planned
to hold all ESA Planetary missions datasets. The first version was released in
2004 March with Giotto data and some Rosetta calibration data. In the last two
years, Mars Express, Rosetta, Huygens and Smart-1 data have been ingested into
the Archive. All future ESA planetary missions (Venus Express, BepiColombo)
data will also be part of the PSA. This archive hosts about 3 TB of data. Also
based on the XSA architecture, the PSA offers similar power-search, view, and
retrieving capabilities. Furthermore, a PSA Validation Tool has been developed
to allow the Mission Instruments Teams to validate their datasets against the
PDS standards before they are ingested into the PSA.
3. Conclusions
For developing Science Archives, a Science Archives Team at ESAC, Spain,
has been created within the ESA RSSD Astronomy Science Operations Division.
This group provides horizontal support to various mission archive projects.
2 http://xmm.esac.esa.int/xsa
3 http://integral.esac.esa.int/isda
4 http://www.rssd.esa.int/PSA

706 Arviset et al.
Figure 2.
ESA Science Archives snapshots
People are working for several projects at the same time, ensuring knowledge
transfer and re-use. By using a flexible multi-tier architecture and modern technology
(Java, XML), archive projects can re-use design and code from earlier
projects, which brings down development and maintenance costs, while speeding
up development times. The modular approach will allow evolution and ports
of subsystems without affecting the other systems, thus assisting in preserving
efficient, long-term access to the data from ESA’s science missions. This design
allows a high level of interoperability with other external archives and has
been applied in the context of the Astronomical Virtual Observatory initiatives,
where ESAC Science Archives Team plays an active role. This strategy has already
been put in place for the ISO, XMM-Newton and Integral SOC Archives,
as well as for the Planetary Missions (Giotto, Mars Express, Huygens, Rosetta,
and Smart-1); it will be used for future missions, including Herschel, Planck,
and Gaia.
References
Arviset, C., et al. 2007, in ASP Conf. Ser. 376, ADASS XVI, ed. R. A. Shaw, F. Hill,
& D. J. Bell (San Francisco: ASP), 163
Barbarisi, I., et al. 2007, in ASP Conf. Ser. 376, ADASS XVI, ed. R. A. Shaw, F. Hill,
& D. J. Bell (San Francisco: ASP), 611