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GLAST - LAT ICHEP 2008 - Philadelphia, PA Aug 1, 2008 R.Dubois1/21 GLAST Large Area Telescope: Launched and Being Commissioned Richard Dubois Stanford.

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Presentation on theme: "GLAST - LAT ICHEP 2008 - Philadelphia, PA Aug 1, 2008 R.Dubois1/21 GLAST Large Area Telescope: Launched and Being Commissioned Richard Dubois Stanford."— Presentation transcript:

1 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois1/21 GLAST Large Area Telescope: Launched and Being Commissioned Richard Dubois Stanford Linear Accelerator Center for the LAT Collaboration

2 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois2/21

3 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois3/ Degree Orbit SAA Circular orbit, 565 km altitude (96 min period), 25.6 deg inclination

4 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois4/21 GLAST LAT Collaboration United States California State University at Sonoma 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 Stanford University (SLAC and HEPL/Physics) University of Washington Washington University, St. Louis France IN2P3, CEA/Saclay Italy INFN, ASI Japanese GLAST Collaboration Hiroshima University ISAS, RIKEN Tokyo Inst of Technology Swedish GLAST Collaboration Royal Institute of Technology (KTH) Stockholm University PI: Peter Michelson PI: Peter Michelson (Stanford & SLAC) ~270 Members (including ~90 Affiliated Scientists, plus 37 Postdocs, and 48 Graduate Students) Cooperation between NASA and DOE, with key international contributions from France, Italy, Japan and Sweden. Managed at Stanford Linear Accelerator Center (SLAC).

5 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois5/21 Two GLAST instruments: –LAT: high energy (20 MeV – >300 GeV) –GBM: low energy (8 keV – 30 MeV) Huge field of view –LAT: 20% of the sky at any instant; in sky survey mode, expose all parts of sky for ~30 minutes every 3 hours. GBM: whole unocculted sky at any time. Huge energy range, including largely unexplored band 10 GeV GeV Large leap in all key capabilities, transforming our knowledge of the gamma-ray universe. Great discovery potential. Large Area Telescope (LAT) GLAST Burst Monitor (GBM) GLAST Key Features Spacecraft Partner: General Dynamics Compared to EGRET: > 100 MeV, 1 yr sensitivity x25 localization x10 2 field of view x5 observing efficiency x2 deadtime x10 -3 Compared to EGRET: > 100 MeV, 1 yr sensitivity x25 localization x10 2 field of view x5 observing efficiency x2 deadtime x10 -3

6 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois6/21 Some Questions GLAST Will Address How do super massive black holes in Active Galactic Nuclei create powerful jets of material moving at nearly light speed? What are the jets made of? What are the mechanisms that produce Gamma-Ray Burst (GRB) explosions? What is the energy budget? What is the origin of the cosmic rays that pervade the galaxy? How does the Sun generate high-energy gamma-rays in flares? How has the amount of starlight in the Universe changed over cosmic time? What are the unidentified gamma-ray sources found by EGRET? What is dark matter? 9 yrs EGRET1 yr (sim) GLAST

7 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois7/21 Experimental Technique Instrument must measure the direction, energy and arrival time of gamma rays over a large energy range (~20 MeV to > 300 GeV)  e+e+ e–e– calorimeter (energy measurement) particle tracking detectors conversion foil anticoincidence shield Pair-Conversion Telescope Technique: Pair Conversion Telescope –Concept: Photon interactions in GLAST energy range dominated by pair conversion –Determine the photon direction –Clear signature for background rejection –Basic requirements Must detect gamma-rays with high efficiency Must be able to reject much larger flux (10 4 :1) of cosmic ray backgrounds Must have a large acceptance (Field Of View) Must have good energy resolution over wide range of incident photon energies Some Definitions: –Effective Area (A eff ): (Total Geometric Acceptance) (conversion probability) (all detector and reconstruction efficiencies). Real rate of detecting gamma rays is (flux) Aeff –Point Spread Function (PSF): Angular resolution of instrument, after all detector and reconstruction algorithm effects. The 2-dimensional 68% containment is the equivalent of ~1.5  (1-dimensional error) if purely Gaussian response. The non- Gaussian tail is characterized by the 95% containment, which would be 1.6 times the 68% containment for a perfect Gaussian response.

8 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois8/21 The GLAST Observatory GBM Bismuth Germanate Detector GBM Sodium Iodide Detector LAT

9 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois9/21 e+e+ e–e–  Overview of LAT Precision Si-strip Tracker (TKR)Precision Si-strip Tracker (TKR) 18 XY tracking planes. Single-sided silicon strip detectors (228  m pitch) Measure the photon direction; gamma ID. Hodoscopic CsI Calorimeter(CAL)Hodoscopic CsI Calorimeter(CAL) Array of 1536 CsI(Tl) crystals in 8 layers. Measure the photon energy; image the shower. Segmented Anticoincidence Detector (ACD)Segmented Anticoincidence Detector (ACD) 89 plastic scintillator tiles. Reject background of charged cosmic rays; segmentation removes self-veto effects at high energy. Electronics SystemElectronics System Includes flexible, robust hardware trigger and software filters. Systems work together to identify and measure the flux of cosmic gamma rays with energy 20 MeV - >300 GeV. Calorimeter Tracker ACD [ surrounds 4x4 array of TKR towers]

10 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois10/21 LAT Construction: An International Effort Tracker: US, Italy, Japan Calorimeter: US, France, Sweden ACD: US Integration & Data System: US

11 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois11/21 GN HEASARC - - DELTA 7920H White Sands TDRSS SN S & Ku LAT Instrument Science Operations Center (SLAC) GBM Instrument Operations Center GRB Coordinates Network Telemetry 1 kbps - S Alerts Data, Command Loads Schedules Mission Operations Center (MOC) GLAST Science Support Center  sec GLAST Spacecraft Large Area Telescope & GBM GPS GLAST MISSION ELEMENTS

12 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois12/21 Operating modes In survey mode, the LAT observes the entire sky every two orbits (~3 hours), each point on the sky receives ~30 mins exposure during this time. GBM sees entire unocculted sky. Multiwavelength campaigns with the LAT will be limited only by the ability to coordinate to other observations in other wavebands. Can also perform pointed observations of particularly interesting regions of the sky. LAT sensitivity on 4 different timescales: 100 s, 1 orbit (96 mins), 1 day and 1 year

13 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois13/21 In Orbit: Single Events in the LAT The green crosses show the detected positions of the charged particles, the blue lines show the reconstructed track trajectories, and the yellow line shows the candidate gamma-ray estimated direction. The red crosses show the detected energy depositions in the calorimeter.

14 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois14/21 Calorimeter Calibration with Ions Ion peaks are used for calibrations Heavy ions probe the higher energy ranges Peak positions stable to < 1% over days elapsed Proton MIP Non-Interacting Heavy Ion C N O Fe Carbon peak vs time

15 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois15/21 Vela – early returns Soup to nuts: everything works! timing background rejection alignment precise ephemerides of many pulsars provided by Parkes, Jodrell Bank, Green bank, Nançay, Arecibo, Hartbeesthoek, Urumqi, RXTE, XMM... good timing of the EGRET pulsars EGRET selecting on-pulse shows point source evaluate PSF alignment of LAT to sky (fit to several point sources) on-pulse off-pulse

16 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois16/21 Rates & Deadtime ~2 kHz trigger rate ~500 Hz downlink rate ~1 Hz source photon rate 26  s deadtime: for GRBs! Software filter on board reduces downlink rate to ~500 Hz 100:1 background rej done on ground Oscillations due to geomagnetic latitude variations and orbital effects

17 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois17/21 GLAST/LAT performance Energy Resolution: ~10% (~5% off-axis) PSF (68%) at 100 MeV ~ 3.5 o (thin section) PSF (68%) at 10 GeV ~ 0.1 o Field Of View: 2.4 sr Point Source sens. (>100 MeV): 3x10 -9 cm -2 s -1

18 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois18/21 Year 1 Science Operations Timeline Overview L AUNCH L +60 days week week week week month 12 m o n t h s spacecraft turn-on checkout LAT, GBM turn-on check out “first light” whole sky initial tuning/calibrations pointed + sky survey tuning Start Year 1 Science Ops Start Year 2 Science Ops in-depth instrument studies sky survey + ~weekly GRB repoints + extraordinary TOOs Release Flaring and Monitored Source Info GBM and LAT GRB Alerts continuous release of new photon data Observatory renaming GI Cycle 1 Funds Release Fellows Year 1 Start LAT 6-month high-confidence source release, GSSC science tools advance release GI Cycle 2 Proposals LAT Year 1 photon data release PLUS LAT Year 1 Catalog and Diffuse Model 2nd GLAST Symposium

19 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois19/21 Data Release plan and operations First Year observations - Sky Survey –After initial on-orbit checkout (60 days), the first year of observations will be a sky survey. –Repoints for bright bursts and burst alerts will be enabled –Extraordinary ToOs will be supported. –First year data will be used for detailed instrument characterization and key projects (catalog, background models etc). First Year Data release –All GBM data –Information on all LAT detected GRB (flux, spectra, location) –High level LAT data (time resolved flux/spectra) on ~20 selected sources and on all sources which flare above 2x10 -6, continued until the source flux drops below 2x10 -7 (rate ~ 1-4 such objects per month). –The LAT team will produce a preliminary source list after ~6 months on a best effort basis Subsequent years: Observing plan driven by guest observer proposal selections by peer review. Default is sky survey mode. –All data publicly released within 72 hours through the Science Support Center (GSSC). See for more detailshttp://glast.gsfc.nasa.gov/ssc/data/policy/

20 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois20/21 LAT First Year Source Monitoring List provided for daily and weekly integrations for all sources. a “quicklook” analysis, priority is to get the results out as quickly as possible. Tables will be updated as analysis and calibrations improve.

21 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois21/21 The LAT’s First Public Volley: 3C454.3 ATel

22 GLAST - LAT ICHEP Philadelphia, PA Aug 1, 2008 R.Dubois22/21 Outlook LAT Launch and Turn On have been huge successes!! –Commissioning nearly complete: no real surprises yet. LAT is stable! –Initial post-launch calibrations complete –Enter survey mode after L+60 –Will already have surpassed the EGRET dataset –First year data will be used for detailed instrument characterization and key projects (catalog, background models etc). First Year Data release –Start releasing GRBs & selected light curves in mid August –preliminary source catalog after ~6 months on a best effort basis GLAST to be renamed in “First Light” ceremony on Aug 5 Lots of excitement to come!


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