1. Gamma-Ray Telescopes

2. Brief History of Gamma Ray Astronomy 1961 EXPLORER-II: First detection of high-energy  -rays from space 1967 VELA satelllites: Discovery of  -ray bursts (not published until 1973) 1968 OSO-3: Discovery of > 100 MeV  -ray emission from the Milky Way 1972 SAS-2: First high-energy  -ray images; discovery of Geminga pulsar 1975 COS-B: First detailed  -ray map of the Milky Way with 24 point sources 1979 HEAO-3: Discovery of radioactive 26 Al emission in the Milky Way 1981 SMM: Studies of solar flare  -ray emission; 56 Co-lines from SN 1987A 1987 Whipple (ACT): First credible detection of a TeV source (Crab Nebula) 1989 SIGMA: First high-resolution images (13’) in hard X-rays / soft  -rays 1991 CGRO: First all-sky survey of the  -ray sky; major discoveries in all areas of  -ray astronomy;  -ray astronomy becomes an integral part of astronomy 1997 BeppoSAX: First high-precision localization of  -ray bursts; cosmological origin of GRBs established 2002 INTEGRAL: Major advances in high-resolution imaging and spectroscopy of Galactic  -ray sources 2004 Swift: Dedicated  -ray burst mission: prompt X-ray/optical follow-up; arcsecond localization of GRBs 2008 Fermi (GLAST): All-sky monitoring of the MeV – GeV sky every 3 hr with sensitivity a factor of > 10 better than EGRET.

3. 1) The Compton Gamma Ray Observatory (CGRO) (1991 – 2000) Oriented Scintillation- Spectrometer Experiment (OSSE): ~ 0.1 – 10 MeV Compton Telescope (COMPTEL): ~ 1 – 30 MeV Energetic Gamma-Ray Experiment Telescope (EGRET): pair conversion telescope, ~ 20 MeV – 30 GeV Burst and Transient Source Experiment (BATSE): 0.015 – 110 MeV

4. 2) The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) Launched 2002 Two  -ray telescopes: Imager on Board the INTEGRAL Satellite (IBIS), optimized for high spatial resolution; Spectrometer on INTEGRAL (SPI), optimized for high spectral resolution. Energy range: ~ 20 keV – 8 MeV Both use coded-mask technique for imaging.

5. 3) AGILE (Astro-rivelatore Gamma a Immagini LEggero) Similar technology and capabilities as EGRET, intended to bridge the gap between EGRET and Fermi (GLAST) Italian gamma-ray satellite mission; launched April 23, 2007 Two instruments: Gamma-Ray Imaging Detector (GRID): 30 MeV – 50 GeV SuperAGILE: 18 – 60 keV

6. 4) The Fermi Gamma-Ray Space Telescope (formerly: Gamma Ray Large Area Space Telescope (GLAST) Launched June 11, 2008 Similar technology as EGRET (pair conversion), but much improved sensitivity, large field of view (~  sr), and slightly extended energy range (~ 20 MeV – 300 GeV). Will operate in constant slewing mode to survey the sky for flaring high-energy  - ray sources: One full-sky scan every 3 hr.

7. Fermi Two main science instruments: LAT (Large Area Telescope) GBM (GLAST Burst Monitor)

8. The Large Area Telescope (LAT) Pair Conversion Telescope QuantityLATEGRET Energy Range20 MeV – 300 GeV20 MeV – 30 GeV Peak Effective Area> 8000 cm 2 1500 cm 2 Field of View> 2 sr0.5 sr Angular Resolution< 3.5 o (at 100 MeV) 10 GeV) 5.8 o (at 100 MeV) Point Source Sensitivity< 6*10 -9 cm -2 s -1 10 -7 cm -2 s -1

9. The LAT First-Light All-Sky Map All-Sky Map

10. The GLAST Burst Monitor (GBM) All-sky Monitor optimized to detect X-ray / soft  -ray flashes (~ 8 keV – 30 MeV) Source localization to < 15 o

11. 5) Atmospheric Cherenkov Telescopes ExperimentTechniqueE thr (TeV)Location WhippleIACT0.25Arizona, USA HEGRA-IACTIACT array0.50Canary Islands CANGAROO-IIIACT0.1Woomera, Australia HEGRA-AIROBICCWavefront sampling 15Canary Islands ThemistocleWavefront sampling 3Themis, France STACEESolar Tower ACT0.05Albuquerque, NM, USA HESSIACT array0.04Gamsberg, Namibia MAGICIACT0.01Canary Islands VERITASIACT array0.05Arizona, USA