Using Product Access Layer to isolate the complexity of data storage from Herschel users

Launched on May 14, 2009, ESA's Herschel Space Observatory is the largest astronomical telescope ever launched. It is in routine science operations and has already generated data for more than 25000 observations. The users of Herschel data products are astronomers, data processing software developers, instrument engineers, and calibration scientists. Different users have different scenarios and requirements on data access. Different data storage systems and mechanisms (including commercial Object Oriented database, Herschel Science Archive, local disk, remote HTTP server and so on) are selected to build up data processing applications. We developed a software package named Product Access Layer (PAL) to hide the complexity of data storage systems from users. It contains an implementation-independent interface to store, query and retrieve all kinds of data products. PAL helps users to focus on scientific data processing and analysis. It has become a fundamental component of the Herschel Interactive Processing Environment (HIPE), which is the main application interface for most Herschel users.