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GLAST Status Briefing at NASA HQ: Overview of Gamma-Ray Detection Technology

On September 14, 1999, T. Burnett from the University of Washington presented a detailed briefing on the GLAST (Gamma-ray Large Area Space Telescope) project at NASA Headquarters. Key topics included the capability to detect gamma rays ranging from 30 MeV to 300 GeV, the innovative design utilizing plastic scintillators and CsI crystals for energy measurement, and the advanced multi-level trigger systems. The discussion also covered Monte Carlo simulations for signal/noise optimization, computing challenges, data filtering strategies, and collaborations for the project's development, with a timeline leading to the anticipated launch in 2005.

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GLAST Status Briefing at NASA HQ: Overview of Gamma-Ray Detection Technology

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  1. REE / GLAST Status Briefing at NASA HQ 14 Sept. 1999 T. Burnett University of Washington

  2. GLAST basics • Detect gamma rays from 30 MeV to 300 GeV • Pair conversion in high-Z material • Energy measurement in CsI crystals • Science: GRB’s, AGN’s, EBL, WIMPs, …

  3. The “baseline” design • ACD: plastic scintillator that cover top and sides. • Tracker: 18 “trays” with Pb foil, Si strip detectors (220 micron pitch)(1.0 M strips!) • Calorimeter: 8 layers of 12 bars2 photo diodes at each enddynamic range: 0.1 MeV - 1 TeV • Multi-level trigger (1,2,3), readout T. Burnett, NASA REE briefing

  4. Simulation Thorough investigation by detailed Monte Carlo simulations: • Cosmic-ray rejection of 5105:1 with 80% gamma-ray efficiency. Signal/Noise >20::1 for extragalactic diffuse gammas. • Predictions for effective area and resolution (verified by beam tests). • Design for the multi-level trigger. • Design optimization. p  A 10-GeV cosmic ray proton striking the calorimeter. A 100 MeV gamma ray proton converting in the tracker. T. Burnett, NASA REE briefing

  5. On-board computing challenges • Rates: must filter ~10 kHz triggers to ~10 Hz for download • Multi-level filter strategy • Channels: ~106 in 33 detectors • Calibration, monitoring • Processors: 34 in loose network • Distribute tasks, monitor processors as well • Note: no single compute-intensive task T. Burnett, NASA REE briefing

  6. GLAST Status • AO just released, November due date • Two major responses expected • SiliconGLAST (my collab.) • FiberGLAST • New start 2002 • Launch 2005 T. Burnett, NASA REE briefing

  7. Association with REE • Support for Stanford and University of Washington for 1.5 yr. • Big help in development of detailed source and detector simulation needed to predict science potential and optimize design • Stimulated multi-process design ideas • Timing such that little chance for REE-developed hardware to be used T. Burnett, NASA REE briefing

  8. data L3 L3 L3 L3 L3 L3 L2 L2 L2 L2 L2 Multi-processor app for REE testbed L2 MC data, each trigger Distribute each tower’s data Combine L2 outputs to available L3 T. Burnett, NASA REE briefing

  9. GPC GPC GPC GPC GPC GPC GPC GPC GPC GPC GPC GPC GPC GPC GPC GPC I/O Server I/O Server Power/ Reset Array Bulk Mem :: Bulk Mem Experiment Experiment COMM Eng’g SS Eng’g SS SCC REE model for spacecraft computing T. Burnett, NASA REE briefing

  10. Fault tolerance • REE contribution to GLAST • Hierarchical • System: the REE Executive (REX) • Identify processor failure • Algorithm/procedure level (Process Executive) • Local error recovery • Sent heartbeat to REX T. Burnett, NASA REE briefing

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