Building from Where We Are: Web Services and Java-Based Clients to Enable Virtual Observatories

The Space Physics Data Facility at NASA Goddard has developed a strong foundation in space science mission services and data for enhancing the scientific return of space physics research and enabling integration of these services into the emerging Virtual discipline Observatory (VxO) paradigm. We are deploying a critical set of foundation components, leveraging our data format expertise and our existing and very popular science and orbit data web-based services, such as Coordinated Data Analysis Web [CDAWeb] and Satellite Situation Center Web [SSCweb]. We have developed web services APIs for orbit location, data finding across FTP sites and in CDAWeb, data file format translation, and data visualizations that tie together existing data holdings, standardize and simplify their use, and enable much enhanced interoperability and data analysis. We describe the technologies we've developed, our experiences and lessons-learned in implementing them, why we chose some technologies over others (web services vs. CORBA or simple CGI, Java vs. JavaScript or Flash), what we might do differently now, and our future direction. We discuss the difficulties in maintaining compatibility and inter-operability through various versions of web services and in merging various client projects, while adding extended functionality such as sonification interfaces in a modular fashion.