Ten years of software sustainability at the Infrared Processing and Analysis Center.

This paper presents a case study of an approach to sustainable software architecture that has been successfully applied over a period of 10 years to astronomy software services at the NASA Infrared Processing and Analysis Center (IPAC), Caltech (http://www.ipac.caltech.edu). The approach was developed in response to the need to build and maintain the NASA Infrared Science Archive (http://irsa.ipac.caltech.edu), NASA's archive node for infrared astronomy datasets. When the archive opened for business in 1999 serving only two datasets, it was understood that the holdings would grow rapidly in size and diversity, and consequently in the number of queries and volume of data download. It was also understood that platforms and browsers would be modernized, that user interfaces would need to be replaced and that new functionality outside of the scope of the original specifications would be needed. The changes in scientific functionality over time are largely driven by the archive user community, whose interests are represented by a formal user panel. The approach has been extended to support four more major astronomy archives, which today host data from more than 40 missions and projects, to support a complete modernization of a powerful and unique legacy astronomy application for co-adding survey data, and to support deployment of Montage, a powerful image mosaic engine for astronomy. The approach involves using a component-based architecture, designed from the outset to support sustainability, extensibility and portability. Although successful, the approach demands careful assessment of new and emerging technologies before adopting them, and attention to a disciplined approach to software engineering and maintenance. The paper concludes with a list of best practices for software sustainability that are based on 10 years of experience at IPAC.