NASA's Earth Observing System Data and Information System (EOSDIS) is a comprehensive data and information system designed to perform a wide variety of functions in support of a heterogeneous national and international user community. To this end, EOSDIS provides a spectrum of services: some services are intended for a diverse group of casual users, some are intended only for a select cadre of research scientists chosen by NASA's peer-reviewed competitions, and many fall somewhere in between. The primary services provided by EOSDIS are User Support, Data Archive, Management, and Distribution, Information Management, and Product Generation, all of which are managed by NASA's Earth Science Data and Information System (ESDIS) Project. Two additional EOSDIS services, Spacecraft Command and Control and Data Capture and Telemetry Processing, are managed by NASA's Earth Science Mission Operations (ESMO) Project. EOSDIS services are described below.
The vast majority of people who interact with EOSDIS do so via NASA's Distributed Active Archive Centers (DAACs). The DAACs have User Support Services to assist users in data acquisition, search, access, and usage. While most of the interaction by users with EOSDIS is through human-computer interfaces or computer-to-computer interfaces, occasional consultation is needed with the User Support Services staff for assistance with specialized questions regarding the data or the system. The DAACs provide support services to users from both the public and private sectors, including research scientists, educators, students, users in public agencies responsible for operational applications such as weather forecasts and environmental monitoring, policy makers, and the public in general.
Data Archive, Management, and Distribution
A list of current EOSDIS data holdings is available through the links found in the Data section. This list includes data products derived from the satellite missions and scientific campaigns, along with other related data and information. EOSDIS stores all the standard products computed from NASA's Earth Observing System (EOS) instruments during their mission life, and distributes requested data to users electronically (via networks). EOSDIS also stores and distributes data from non-EOS sources that are needed for EOS standard product generation. In addition, product generation algorithms, software, documentation, calibration data, engineering, and other ancillary data are stored and provided to users upon request. Sufficient information is stored about the system configuration history to be able to regenerate products in case of accidental or catastrophic loss. Access to the current suite of EOSDIS data holdings may be obtained via the DAACs.
EOSDIS provides convenient mechanisms for locating and accessing products of interest. The "look and feel" of the system is intuitive and uniform across the multiple nodes from which EOSDIS can be accessed. EOSDIS facilitates collaborative science by providing extensible sets of tools and capabilities that allow investigators to provide access to special products (or research products) from their own computing facilities. EOSDIS provides middleware called Common Metadata Repository (CMR) that provides Application Programmer Interfaces (APIs) through which search and access software (clients) can be developed. Client interfaces permit users to access Earth science data archives, browse data holdings, select data products, and place data orders. These gateways provide access to EOSDIS data products plus other Earth science data; only the EOSDIS products include the EOS suite of metadata attributes and values to enhance search capabilities. In addition, specialized services at each of the DAACs can be accessed via their individual interfaces.
EOSDIS supports data product generation from EOS instrument observations. Algorithms and software for EOS data products are generated by EOS investigators as a part of their scientific studies. The algorithms and specifications for standard products are reviewed by NASA through a peer review process to ensure the completeness and consistency needed to satisfy the goals of NASA's EOS mission. Priorities for the processing and reprocessing needed to generate standard products depend on scientific requirements, technical considerations, and cost. Such priorities are determined by the respective instrument teams and EOS Project scientists based on recommendations from the national and international Earth science community.
Spacecraft Command and Control
EOSDIS performs planning and scheduling for spacecraft and instruments, as well as command and control. These functions include processing data acquisition requests, coordinating of multi-instrument observations, ensuring that the commands generated are valid and within resource constraints, monitoring and maintenance of the health and safety of spacecraft and instruments, analyzing spacecraft data, and maintaining a history of spacecraft and instrument operations. EOSDIS also provides appropriate interfaces to ensure command and control of International Partners' instruments aboard EOS spacecraft, and EOS instruments aboard non-EOS spacecraft.
Data Capture and Telemetry Processing
EOSDIS captures science data from all EOS spacecraft and processes them to remove telemetry errors, eliminate communication artifacts, and create Level 0 Standard Data Products that are "raw" data as measured by the instruments (see the Science Data Product Level Definitions). Some EOS instruments are designated as prototype operational environmental monitoring instruments. The data from those instruments are made available within three hours of observation to the National Oceanic and Atmospheric Administration to support operational weather forecasts. For EOS instruments flying on non-EOS spacecraft, the EOS instrument data are captured by the respective ground systems and received by EOSDIS for higher-level data processing, archiving, and distribution.