the eight DAACs. Each DAAC would be focused mainly on a particular Earth system component or discipline, such as atmospheres, oceans, land, snow and ice, hydrology, radiation and chemistry, and even socio-economic influences.

NEED FOR THE EOSDIS

Four primary spacecraft make up the long-term measurement system of the EOS mission. They are Terra, launched in December 1999, Aqua launched in May 2002, ICESat launched in January 2003, and Aura to be launched in 2004. In addition to the processing of the instrument data from these satellites, the EOSDIS has responsibility for the archival and management of all NASA Earth science mission data products prior to EOS as well as data from NASA instruments flown on foreign satellites. The NASA Earth Science Enterprise is responsible for assuring the long-term permanent preservation of these data and has negotiated agreements with the operational agencies (NOAA and USGS) for their permanent retention. EOSDIS will support migration of the data to these agencies.

The EOSDIS performs flight operations for the above four EOS spacecraft; processes, archives, and distributes data from 17 instruments on six EOS spacecraft; and archives and distributes data from more than 40 instruments from more than 15 EOS and non-EOS spacecraft. The system today serves approximately 2 million users per year internationally, archiving almost 4 terabytes per day, distributing about 2 terabytes per day and maintaining the current archive, which is larger than 3 petabytes and is growing. In addition, the system supports 1,800 different data types, manages some of the nation’s largest spatial databases, interfaces with over 35 external systems and depends on more than a million lines of code, with more than 60 commercial off-the-shelf products integrated with custom code deployed on a variety of vendor servers. This system is unprecedented in scope and scale for a NASA mission, and one of the largest, if not the largest, working civilian scientific data system ever built.

What distinguishes the EOSDIS from any of the above space mission data systems are the massive volumes of data ingested, processed into higher-level standard products and archived within hours to a few days of acquisition, and distributed to a broad user community on a routine basis.

Over the decade-long period of planning and implementation, the architecture and design of the EOSDIS have undergone nearly continuous evolution to incorporate new technologies and changing science requirements. In addition to managing a relatively large number of research instru-



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