GLAST The Gamma-ray Large Area Space Telescope The GLAST Mission AGILE-GLAST Workshop

1. GLAST The Gamma-ray Large Area Space Telescope The GLAST Mission AGILE-GLAST Workshop Guido Barbiellini University and INFN Trieste GLAST SSAC for the GLAST LAT collaboration

2. Outline • Context • From SRD to real instrument • Instruments (LAT & GBM) • Capabilities, status • Operations and data • Summary

3. GLAST Key Features • Next-generation high energy gamma-ray observatory • Huge field of view, optimized for sky survey • Full sky every 3 hours. • Huge energy range, including largely unexplored 10 GeV - 100 GeV band • Unprecedented sensitivity • Will transform the HE gamma-ray catalog: • By > order of magnitude in number of point sources • Sub-arcmin localizations (source-dependent) • Map spatially extended sources Large Area Telescope (LAT) Large Area Telescope (LAT) PI: P. Michelson (Stanford University) 20 MeV – >300 GeV GLAST Burst Monitor (GBM) PI: C. Meegan (NASA/MSFC) Co-PI: G. Lichti (MPE) 10 keV – 30 MeV Launch: January 2008 5 year mission life (10 year goal) GLAST Burst Monitor (GBM)

4. The EGRET legacy The Compton Gamma Ray Observatory (CGRO) is a sophisticated satellite observatory dedicated to observing the high-energy Universe. It is the second in NASA's program of orbiting "Great Observatories", following the Hubble Space Telescope. While Hubble's instruments operate at visible and ultraviolet wavelengths, Compton carries a collection of four instruments which together can detect an unprecedented broad range of high-energy radiation called gamma rays. These instruments are the Burst And Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma Ray Experiment Telescope (EGRET).

5. The EGRET legacy

6. The EGRET legacy Kouveliotou et al 1994 Sommer et al. 1994

7. GLAST requirements

8. GLAST requirements

9. GLAST requirements

10. GLAST requirements

11. GLAST requirements

12. GLAST requirements

13. GLAST requirements

14. GLAST requirements

15. GLAST requirements

16. GLAST requirements

17. GLAST requirements

18. GLAST requirements

19. GLAST requirements

20. provides spectra for bursts from 10 keV to 30 MeV, connecting frontier LAT high-energy measurements with more familiar energy domain; provides wide sky coverage (8 sr) -- enables autonomous repoint requests for exceptionally bright bursts that occur outside LAT FOV for high-energy afterglow studies (an important question from EGRET); provides burst alerts to the ground. GLAST requirements Simulated GBM and LAT response to time-integrated flux from bright GRB 940217 Spectral model parameters from CGRO wide-band fit 1 NaI (14 º) and 1 BGO (30 º)

21. GLAST requirements

22. GLAST requirements

23. Scientific Requirements Document

24. The Anti Coincidence Detector vetoes incoming charged particles g The reconstructed vertex points back to the  source Track of a charged particle, measured by position sensitive detectors Conversion foil: the photon interacts to produce an ee+ pair e– e+ The Calorimeter measures the photon energy HE Gamma Ray Telescope • Pair production telescope for high energy gamma rays • Tracker, calorimeter, and anti-coincidence shield work together to measure direction and energy of g-rays and reject background • Optimization • Angular resolution: many thin layers of fine-pitch TKR • Energy resolution: thick-as-possible CAL, segmented to measure shower profile • Rejection: efficient ACD particle detection, segmented to minimize self-veto from g-ray shower backsplash

25. GLAST LAT Collaboration • United States • University of California at Santa Cruz - Santa Cruz Institute of Particle Physics • Goddard Space Flight Center – Laboratory for High Energy Astrophysics • Naval Research Laboratory • Ohio State University • Sonoma State University • Stanford University (SLAC and HEPL/Physics) • University of Washington • Washington University, St. Louis • France • IN2P3, CEA/Saclay • Italy • INFN, ASI, INAF • Japanese GLAST Collaboration • Hiroshima University • ISAS, RIKEN • Swedish GLAST Collaboration • Royal Institute of Technology (KTH) • Stockholm University PI: Peter Michelson(Stanford & SLAC) ~230 Members (including ~184 Affiliated Scientists, plus 24 Postdocs, and 36 Graduate Students) Cooperation between NASA and DOE, with key international contributions from France, Italy, Japan and Sweden. Managed at Stanford Linear Accelerator Center (SLAC).

26.  e– e+ Large Area Telescope (LAT) Overview • Precision Si-strip Tracker (TKR) • 18 XY tracking planes. Single-sided silicon strip detectors (228 mm pitch), 880,000 channels. • Tungsten foil converters • 1.5 radiation lengths • Measures the photon direction; gamma ID. • Hodoscopic CsI Calorimeter(CAL) • Array of 1536 CsI(Tl) crystals in 8 layers. 3072 spectroscopy chans. • 8.5 radiation lengths • Hodoscopic array supports bkg rejection and shower leakage correction • Measures the photon energy; images the shower. • Segmented Anticoincidence Detector (ACD) • 89 plastic scintillator tiles. • Rejects background of charged cosmic rays; segmentation minimizes self-veto effects at high energy. • Electronics System • Includes flexible, robust hardware trigger and software filters. Tracker ACD [surrounds 4x4 array of TKR towers] Calorimeter Systems work together to identify and measure the flux of cosmic gamma rays with energy 20 MeV - >300 GeV.

27. LAT Instrument Performance • Performance significantly improved over EGRET • Improved angular resolution, effective area, and FOV • Point-source sensitivity ~ 4 × 10-9 ph cm-2 s-1 • Factor of 25 better than EGRET • Expect source catalog to contain several thousand objects

28. 12 Sodium Iodide (NaI) Scintillation Detectors 2 Bismuth Germanate (BGO) Scintillation Detectors Major Purposes • Provide low-energy spectral coverage in the typical GRB energy regime over a wide FoV (10 keV – 1 MeV) • Provide rough burst locations over a wide FoV • 5” diameter x 0.5” thickness Major Purpose • Provide high-energy spectral coverage (150 keV – 25 MeV) to overlap LAT range over a wide FoV • 5” diameter x 0.5” thickness Overview of GBM • Provides spectra for GRB from 10 keV to 30 MeV • GBM provides on-board GRB locations over the entire unocculted sky. The observatory can be re-oriented to obtain LAT observations of afterglow from strong bursts.

29. GBM Collaboration National Space Science & Technology Center University of Alabama in Huntsville NASA Marshall Space Flight Center Max-Planck-Institut für extraterrestrische Physik Charles Meegan (PI) Giselher Lichti (Co-PI) On-board processing, flight software, systems engineering, analysis software, and management Detectors, power supplies, calibration, and analysis software

30. GBM System Performance • GBM data types • Time-tagged event data during bursts • Two types of histograms, continuously • One optimized for spectroscopy (8-sec avg, 128 chans) • One optimized for timing (0.25-sec avg, 8 chans) • Burst summary • On-ground location accuracy: < ~ few degrees • Expected GBM burst-detection rate • ~70 bursts per year in FOV of LAT • ~220 bursts per year total ~ 1/3 BATSE sensitivity

31. GBM Hardware Full complement of GBM flight hardware12 NaI detectors, 2 BGO detectors, Power Supply Box, and Data Processing Unit integrated for functional testing at the National Space Science and Technology Center (NSSTC) in Huntsville, AL

32. GLAST Burst Monitor on Spacecraft

33. GLAST

34. GLAST MISSION ELEMENTS GLAST MISSION ELEMENTS Large Area Telescope & GBM m • sec GPS • - • Telemetry 1 kbps GLAST Spacecraft • TDRSS SN S & Ku DELTA 7920H • • S - - • GN • LAT Instrument Science Operations Center White Sands Schedules Mission Operations Center (MOC) GLAST Science Support Center HEASARC GSFC Schedules GRB Coordinates Network GBM Instrument Operations Center Alerts Data, Command Loads

35. After the initial on-orbit checkout, verification, and calibrations, the first year of science operations will be an all-sky survey. every region of the sky viewed for ~30 minutes every 3 hours first year data used for detailed instrument characterization, refinement of the alignment, and key projects (source catalog, diffuse background models, etc.) needed by the community data on transients and “sources of interest” will be released, with caveats repoints for bright bursts and burst alerts enabled extraordinary ToO’s supported workshops for guest observers on science tools and mission characteristics for proposal preparation Observing plan in subsequent years driven by guest observer proposal selections by peer review (default is sky survey mode). Public data released through the science support center (GSSC). Operations Phases, Guest Observers, Data

36. GLAST Science Support Center (GSSC) • Supports guest observer program, provides training workshops, provides data and software to community, archives to HEASARC, joint software development with Instrument Teams, utilizing HEA standards. Located at Goddard. • GSSC tasks: • Data Archive • The server for LAT photons and events is ready and in use for DC2 and SC2. • Operations • Scheduling tool. • Software to support ToOs and to process observing timelines • User Support • Timelines, exposure and count maps, and various reports will be posted on the GSSC website. • The GSSC is actively involved in the Science Analysis Environment (SAE), the definition of the data products, and the writing of documentation and workbooks. see http://glast.gsfc.nasa.gov/ssc/

37. MW Info and Coordination • Multiwavelength observations are key to many science topics for GLAST. • GLAST welcomes collaborative efforts from observers at all wavelengths • For campaigners’ information and coordination, see http://glast.gsfc.nasa.gov/science/multi • To be added to the Gamma Ray Multiwavelength Information mailing list, contact Dave Thompson, djt@egret.gsfc.nasa.gov • GI Program supports correlative observations and analysis • See http://glast.gsfc.nasa.gov/ssc/proposals

38. Conclusions • Simulated LAT sky survey • One year exposure • >100 MeV image EGRET survey >100 MeV, full mission