1. GLAST LAT Project July 19, 2005 E. do Couto e Silva 1/17 Science Verification Analysis and Calibration GLAST Large Area Telescope Eduardo do Couto e Silva SLAC Jul 19, 2005

2. GLAST LAT Project July 19, 2005 E. do Couto e Silva 2/17 Science Verification Analysis and Calibration Objectives –Calibrate the LAT and characterize its performance prior to launch –Maximize science return by optimizing instrument capabilities –Understand systematic effects to extend science reach –Provide input to Instrument Science Operations Center –Develop calibration, monitoring and diagnostics tools to be exercised on-orbit –Strengthen collaboration ties and disseminate knowledge across teams –Instrument analysis workshops ( 5 th meeting scheduled for Aug 29) Data –Cosmic ray secondaries and low energy photons –Collected at several stages of the LAT integration –Particle beam tests –spare LAT modules (after instrument delivery) –Sophisticated Monte Carlo simulations –Comprehensive description of detector geometry and physics processes Data Analysis –Probe a large parameter space of the Large Area Telescope –Search for hardware failures –Debug software –Learn about the operational characteristics of the instrument

3. GLAST LAT Project July 19, 2005 E. do Couto e Silva 3/17 Secondary Cosmic Ray Showers Muon candidates Work from Anders Borgland (SLAC)

4. GLAST LAT Project July 19, 2005 E. do Couto e Silva 4/17 Instrumental Capabilities Energy Resolution requirements –Calibrate Energy Scales –Beam test –Calibrate out non-linear effects Pointing accuracy requirements –Inter and Intra tower alignment

5. GLAST LAT Project July 19, 2005 E. do Couto e Silva 5/17 Calibrate Energy Scales Muon candidates –11.2 MeV peak in CAL crystals We are able to probe effects at the 2% level –improved offline software DataMC Work from David Smith (Bordeaux, France)

6. GLAST LAT Project July 19, 2005 E. do Couto e Silva 6/17 Intra Tower Alignment the ideal tower a horizontal shift a vertical shift a rotation the real tower Work from Michael Kuss (Pisa, Italy)

7. GLAST LAT Project July 19, 2005 E. do Couto e Silva 7/17 Horizontal and Vertical Alignment Aligns: horizontal (  to strips) vertical X4 X3 X2 X1 X0 real position ideal position res =  x +  z · cot(θ) θ horizontal displacement: 157  m vertical displacement: 81  m

8. GLAST LAT Project July 19, 2005 E. do Couto e Silva 8/17 Calibrations Work! Effect is calibrated out for all planes

9. GLAST LAT Project July 19, 2005 E. do Couto e Silva 9/17 Objective –Measure and monitor trigger efficiencies –includes effects from »Gap between Silicon wafers »dead strips »insensitive area »alignment »timing Select muon candidates with TKR –Define a track using 4 layers –3 top and 1 bottom –Test intermediate layers –Measure efficiency –Compare with MC simulations –Direction and position measured by TKR »See next slide TKR Efficiencies Work from Tsunefumi Mizuno et al (Hiroshima, Japan) Tower

10. GLAST LAT Project July 19, 2005 E. do Couto e Silva 10/17 Good agreement between MC and Data within 1% for all 6 towers Tower in Pos#8Tower in Pos#9 TKR Efficiencies: Data/MC Simulation

11. GLAST LAT Project July 19, 2005 E. do Couto e Silva 11/17 Timing of Integrated Systems Need to align TKR/CAL/ACD –To trigger efficiently Need to align TKR/CAL/ACD –To latch data efficiently On-orbit Operations –Trigger alignment knobs are controllable remotely –We are currently acquiring experience on the ground

12. GLAST LAT Project July 19, 2005 E. do Couto e Silva 12/17 Minimizing the Effects of Trigger Jitter Mainly caused by pulse height differences with respect to the trigger threshold –TKR –Large signals from CNO –CAL –Large variation in energy Time-in of towers –Optimize performance –Uniformity across towers Work from Martin Kocian and Su Dong (SLAC)

13. GLAST LAT Project July 19, 2005 E. do Couto e Silva 13/17 Time Between Events: Baseline Run Expect 26.5  s Good agreement! Work from Warren Focke and Anders Borgland (SLAC)

14. GLAST LAT Project July 19, 2005 E. do Couto e Silva 14/17 Probing Several Instrument Configurations We designed a series of tests in which we change only one parameter in the instrument and –Collect cosmic rays –Select muon candidates –Verify the behavior is not affected by parameter changes Example of parameters –Read TKR from “right” or “left” cables only –Change Voltage of Power Distribution Unit –Overlay a source of high rate triggers on the top of existing cosmic ray triggers

15. GLAST LAT Project July 19, 2005 E. do Couto e Silva 15/17 Plane ● Baselin e ● Min ● Max Bottom Plane = 0 Top plane = 35 From Stefano and Claudia (Perugia, Italy) No major discrepancies found so far… Change voltage From Monica Brigida (Bari, Italy) Baseline (read from both sides) Right Readout only Left Readout only

16. GLAST LAT Project July 19, 2005 E. do Couto e Silva 16/17 Cosmic Ray Secondaries: Photon Candidates Work from Leon Rochester (SLAC) and William Atwood (UCSC)

17. GLAST LAT Project July 19, 2005 E. do Couto e Silva 17/17 Summary and Outlook Summary of SVAC activities –Focus on improving and updating calibrations –Explore on-orbit operational aspects of the instrument –As well as we can simulate on the ground –Not part of PASS/FAIL testing –Longer term feedback on instrument characterization –Propose special tests as needed Timeline –Environmental Tests –Data will be delivered to SLAC for offline analysis –Focus on correlating housekeeping with science data –Environmental dependencies of calibrations –Spacecraft Integration –On-orbit checkout –First year of operation