The XMM-Newton SAS - Distributed Development and Maintenance of a Large Science Analysis System: A Critical Analysis


Paper:	The XMM-Newton SAS - Distributed Development and Maintenance of a Large Science Analysis System: A Critical Analysis
Volume:	314, Astronomical Data Analysis Software and Systems XIII
Page:	759
Authors:	Gabriel, C.; Denby, M.; Fyfe, D.J.; Hoar, J.; Ibarra, A.; Ojero, E.; Osborne, J.; Saxton, R.D.; Lammers, U.; Vacanti, G.
Abstract:	The XMM-Newton Scientific Analysis System (SAS) is the software used for the reduction and calibration of data taken with the XMM-Newton satellite instruments leading to almost 400 refereed scientific papers published in the last 2.5 years. Its maintenance, further development and distribution is under the responsibility of the XMM-Newton Science Operations Centre together with the Survey Science Centre, representing a collaborative effort of more than 30 scientific institutes. Developed in C++, Fortran 90/95 and Perl, the SAS makes large use of open software packages such as ds9 for image display (SAO-R&D Software Suite), Grace, LHEASOFT and cfitsio (HEASARC project), pgplot, fftw and the non-commercial version of Qt (TrollTech). The combination of supporting several versions of SAS for multiple platforms (including SunOS, DEC, many Linux flavours and MacOS) in a widely distributed development process which makes use of a suite of external packages and libraries presents substantial issues for the integrity of the SAS maintenance and development. A further challenge comes from the necessity of maintaining the flexibility of a software package evolving together with progress made in instrument calibration and analysis refinement, whilst at the same time being the source of all official products of the XMM-Newton mission. To cope with this requirement, a sophisticated system for continuous integration and testing on several platforms of different branches has been put in place on top of a refined development model designed for this special S/W development case. The SAS is considered now a mature system. We present the different aspects of its development, maintenance and distribution, extracting lessons learned for present and future projects of this magnitude.