1. Fermi Large Area Telescope (LAT) Integration and Test (I&T) Data Experience and Lessons Learned LSST Camera Workshop Brookhaven, March 2012 Tony Johnson (for Richard Dubois) Fermi Data Handling Manager (but not involved in I&T) Most slides from Anders Borgland (Science Verification, Analysis and Calibration manager)

2. Fermi LAT <> LSST We only dealt with I&T for the LAT – not the spacecraft itself (thanks NASA) – NASA did have specific requirements for documenting I&T of LAT

3. Fermi LAT I&T overview Integration and Test – Before we launched Fermi we went through a long Integration & Test phase of the LAT. – We had an EngineeringModel of one of the towers. – When we got the complete towers: Integrated them one by one into the 4x4 grid. – We took cosmic data and Van Der Graf test data along the way In addition we took beam test data on prototype modules – At CERN, SLAC and GSICERNSLACGSI In parallel: – Intense development of Reconstruction/Analysis and Monte Carlo simulations Detector modeling and response – Extensive “Data Challenge” program Wherever possible the same software was used for all of these activities: – Data formats for raw, reconstructed and “housekeeping” data – Reconstruction and Analysis code – Data Catalog, Automated data processing (pipeline) – Electronic logbook

4. Data Products Complete set of data needs to be recorded and cataloged – Needs to remain accessible/usable for 10+ years Test Housekeeping data. Voltages, temperatures, beam conditions, etc Detector configuration, geometry, etc Rawdata DAQ Reconstruction- Analysis Reconstructed data Code versions, configuration, log files, (the code itself?) Electronic log book, formal test report

5. Data Records – Web Interface

6. Software/Tools Evolution Reconstruction/analysis code – Had to deal with both real data taking and MC simulations. – Had to flexible enough to deal with different detector configurations Preferably by configuration files without need to rebuild – Fermi allows detector geometry to be read from XML file Fermi LAT code: – Made up of individual software packages: – Cal reconstruction, Energy estimate, track finding etc. – Version control using cvs Software release: – A collection of a consistent set of software packages: Currently: >90 packages. Called 'GlastRelease'. Original idea: – GlastRelease: MC oriented. Bleeding edge – all development takes part here. – EngineeringModel: A frozen version of GlastRelease for real data taking: – Stable: Resynch to GlastRelease once in a while. – Bug 'free': Bugs fixed in GlastRelease before making it into EngineeringModel

7. Real World Data is different from MC: – Requirements from processing data are different from doing MC. May have to add new features to process data. Data taking schedule is different from MC: – Data taking schedule drives when and how fast to add new features. In short: – EngineeringModel was quite often more advanced than GlastRelease – They diverged to a large degree. – Often out of synch. It was non-trivial to deal with all this The I&T team needs to test new software features/bug fixes quickly: – You usually need bugs fixed yesterday! – You need to give quick feedback to the developers: The more details you can give, the better.... – Excellent communication between I&T team and software developers is essential

8. Lessons Learned Planned well in advance to use common software for I&T and real data taking – Different requirements, timescales make this challenging Planned to use the same tools for I&T and real data – Evolution of software makes this hard – Version of reconstruction software used for I&T is now very old Current code can still read old data – but for how long? Need to record code version used, may need to maintain old versions of software used for I&T – Used electronic logbook, database for housekeeping, data catalog, processing pipeline to record processing history In all cases newer versions of these tools have evolved I&T data is still accessible but in old/obsolete version of tools Need to maintain old tools, or plan to actively migrate data over time