The Gamma-ray Large Area Space Telescope Mission key facts, status Expected first light results

1. Gamma-ray Large Area Space Telescope The Gamma-ray Large Area Space Telescope Mission key facts, status Expected first light results INFN, Commission Scientifica Nazionale II Giornata di aggiornamento sulla Fisica Astroparticellare Laboratori Nazionali del Gran Sasso, 2 Aprile 2008

2. The GLAST gamma-ray observatory – Key Facts • Launch • Date • 16 May 2008 • Location • Kennedy Space Flight Center • Vehicle • Delta II – 2920-10H • Orbit • Altitude • 575 Km • Inclination • 28.5 degrees • Period • 95 minutes • Instruments on board • Large Area Telescope (LAT) • 20MeV – >300GeV • Gamma Burst Monitor • 10KeV – 30MeV • Observing strategy • Survey + Pointing (Autonomous Repoint Request, Target of Opportunities) GLAST at NASA-KSFC for final preparation for launch on may 16 2008 International multi-agency mission

3. Tracker/Converter (TKR): • Silicon strip detectors (single sided, each layer is rotated by 90 degrees with respect to the previous one) • W conversion foils • ~80 m2 of silicon • ~106 electronics chans • fully digital electronics • High precision tracking, small dead time g • Anti-Coincidence (ACD): • Segmented (89 tiles) • Self-veto @ high energy limited • 0.9997 detection efficiency (overall) • Calorimeter (CAL): • 1536 CsI crystals • Analog 4 range readout • 8.5 X0 • Hodoscopic • Shower profile reconstruction (leakage correction) e+ e- The LAT instrument: how we built it • Overall modular design: • 4x4 array of identical towers - each one including a Tracker, a Calorimeter and an Electronics Module. • Surrounded by an Anti-Coincidence shield (not shown in the picture). Page Number

4. LAT Performance http://www-glast.slac.stanford.edu/software/IS/glast_lat_performance.htm Energy dispersion relative Aeff vs g angle at 10GeV 68% containment of the PSF update before pre-launch package Energy dispersion vs g angle on-axis effective area PSF vs g angle at 10GeV

5. LAT Intensity MAP PSF better, somewhat fewer counts thousands new AGN detections expected in years of operation ‘True color’ counts map (red: 100-400 MeV, green: 400-1600 MeV, blue: >1600 MeV) First Light Image vs. EGRET EGRET >300 MeV intensity map, no smoothing LAT Simulation >300 MeV 4days survey (160k g-rays);

6. E>100 MeV – PSF < 3.3o E>1 GeV – PSF < 0.6o First Light Results and validation from the Vela 7 days pointed - Light curve for absolute timing validation Large Effective Area many photons >8kcm2 flat above 1GeV >3kcm2 at 100 MeV fast rising

7. BACKUP

8. g GRID Mechanical backbone e- e+ Electronics & Flying Software Data Acquisition System Overview of the Large Area Telescope Segmented Anticoincidence Detector (ACD) 89 plastic scintillator tiles surrounding the TKR towers Reject background of charged cosmic rays Removes self-veto effects at high energy Precision Si-strip Tracker (TKR) 18 XY tracking planes Single-sided silicon strip detectors 228 mm pitch, 8.8 105 channels Measure the photon direction LAT: 4 x 4 modular array 3000 kg, 650 W Hodoscopic CsI Calorimeter(CAL) Array of 1536 CsI(Tl) crystals in 8 layers 6.1 104 channels Measure the photon energy, image the shower Page Number

9. First Light All-Sky Image • Simulation of 4 days of survey 572k g-rays (cf ~1.4M for EGRET) ‘True color’ counts map (red: 100-400 MeV, green: 400-1600 MeV, blue: >1600 MeV)