NASA Earth Science Gateway: Powered by Standards

By Adena Schutzberg and members of the ESG Team

With all the mapping portals available today on the Web, there's clearly no "one size fits" all that addresses the needs of everyone. Instead, focused portals addressing specific needs are popping up. The user friendliness of the Web means that they can be as accessible to scientists as to students and amateurs. One case in point is NASA's Earth Science Gateway, ESG.

The portal, designed and developed by the NASA Geosciences Interoperability Office (GIO), streamlines access to science and research results, including imagery, models, and visualizations, through open, standard Web protocols. It has a searchable standards-based registry that lets scientists, decision-makers, and anyone with an interest access observations and predictions about natural and human phenomena related to Earth Science and the Earth-Sun System. The data comes from NASA and other sources.

Through a tab titled Find/View, the portal provides access to a variety of maps. Some are already stored and offer insight into forest fires across the U.S, or science data such as sea level pressure and wind parameters. Other maps are created by the user by searching, selecting and organizing layers of data distributed across the Internet and provided by a variety of national and international organizations. These can be saved, printed and shared. Datasets are often downloadable, too. To accommodate the inherent complexities of NASA's research results (e.g. 3D/4D data types), the portal supports the registration and discovery of data coverages (via WCS). The portal is also designed to easily link to advanced visualization and analysis tools that can present the science results in ways that are much more suitable for exploitation in Decision Support Systems.

Under the Hood

The project began in January 2004 and grew out of Open Geospatial Consortium (OGC®) member work on the Geospatial One-Stop Portal Initiative. The decision to use those outcomes was based on NASA's requirements to (1) prototype the use of Web services rooted in consensus based OGC open standards, (2) create improved discovery and access of NASA's research results, and (3) investigate how such standards can help NASA's Earth Science resources such as the Distributed Active Archive Centers (DAACs) and EOS ClearingHOuse (ECHO) to work together in a service-oriented environment. These requirements were aimed at adding value to the users of NASA data and model outputs and supporting their use of earth science research through not only interoperable discovery but also interoperable access to Wweb services. The team began demonstrating the first version of NASA'S ESG in September 2004.

NASA'S ESG relies on these OGC and other standards:

• Catalog Service - Web (CS-W)


• Z39.50 - ANSI/ISO metadata standard


• Web Map Service (WMS)


• Styled Layer Descriptor (SLD)


• Web Feature Service/Web Coverage Service (WFS/WCS, for parsing and registering service descriptions)


• WMS Context


• Gazetteer

The server side of NASA'S ESG is powered by Red Hat Enterprise Linux, equipped with Apache, Tomcat, and Oracle 10g. The portal, including the mapping interface, is part of the Web Enterprise Suite (WES), built by Compusult, Ltd. of Canada. The in-browser client is built with Java portlets conforming to JSR 168, a Java standard for portlets, using the open-source LifeRay product. Of course any client implementing OGC standards can tap into the Web services, too.

Why Standards?

NASA's Earth Science and interdisciplinary research and applications activities require access to earth observations, analytical models and specialized tools and services from diverse distributed sources. Interoperability and open standards for geospatial data access and processing greatly facilitate such access among the information and processing components related to satellite mounted, airborne, and in situ sensors; predictive models; and decision support tools. Most importantly NASA's ESG platform brings together the resources of the NASA Earth Science community into a system that can plug into larger contexts, such as the Global Earth Observing System of System (GEOSS).

Thanks to extensive use of open standards, NASA'S ESG is extensible and flexible and can tap into a wide array of online data services, serve a variety of audiences and purposes, and adapt to technology and business changes. NASA'S ESG provides local and distributed search and harvest; visualization of remote data via Web services; publishing of data and services; and user personalization; all linked and enabled by a flexible relational database.

NASA'S ESG also serves as an example illustrating what can be done with interoperable components, hence serving as a reference implementation for developers of servers and clients to test against. NASA'S ESG facilitates the discovery of new information from many different sources, thereby fostering interdisciplinary, exploratory, and collaborative work as precursors to innovative research, applications, and decisions.

Lessons Learned

The most valuable lessons from NASA experiences with standards and interoperability lie in recognizing the significance of consensus based open standards, Web services interoperability and the extensibility and flexibility of systems that implements those standards. When use of and compliance to these standards is followed, the ease of data and systems interaction vastly increases the potential use of resources both by traditional users as well as new and non-traditional users.

Developing and deploying NASA'S ESG has presented a few challenges. NASA'S ESG's reliance on distributed, independently managed services makes it hard to control its performance, or to troubleshoot errors when they occur. This highlights the importance of rigorous error handling in servers and clients, and of supplementing standards with agreed "best practices" to make component behavior more predictable.

NASA'S ESG has also highlighted the importance of full adherence to standards. Arbitrary shortcuts or simplifying assumptions inevitably lead to errors when drawing on an open ended set of services across different communities of practice with different priorities and assumptions.

Today and Tomorrow

NASA'S ESG is currently in prototype-development mode and is being used and tested by various members of the science community, including the Earth Science Information Partners (ESIP) Federation, Center for International Earth Science Information Network (CIESIN at Columbia University), Washington University DataFed, Italian National Center of Research, George Mason University, and others.

Even as this testing goes on, the NASA'S ESG team is making sure that the different community resources (e.g. Change Master Directory [GCMD], ECHO, Global DAACs) plug in to NASA'S ESG using standard interfaces. It is also working with the ESIP Federation air quality cluster to investigate ways of extending/customizing NASA'S ESG to better meet that community's needs.

The team hopes to expand NASA'S ESG's services capability by registering more services and data sources and using specialized client tools. NASA'S ESG already connects in simple ways to the Space-Time Toolkit, NASA WorldWind, and Google Earth. The hope is to connect to other, more specialized tools for analysis, modeling, and visualization.

In the future, there may be versions of this tool adopted for operational use by NASA's community of practice. NASA's Geosciences Interoperability Office will continue to prototype and testbed advanced architectures and standards towards improved discovery, access, and use of NASA's resources such as, research results, models, and catalogs for societal benefit.