Particle Astrophysics: GLAST

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Particle Astrophysics GLAST
Gamma-ray Large Area Space Telescope

• Peter F. Michelson
• Principal Investigator and Spokesperson, GLAST
  LAT Collaboration
• Department of Physics SLAC,
• Stanford University

SLAC Scientific Policy Committee Meeting May
12, 2001
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Gamma-ray Large Area Space Telescope

• GLAST Observatory
• spacecraft
• LAT
• GBM

• GLAST Mission
• high-energy gamma-ray
• observatory 2 instruments
• - Large Area Telescope
• (LAT)
• - Gamma-ray Burst
• Monitor (GBM)
• launch (Sept 2005)
• Delta 2 class
• mission operations
• science
• - LAT Collaboration
• - GBM team
• - Guest Observers
• lifetime
• 5 years (minimum)

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Large Area Telescope (LAT)
gt 40 times the sensitivity of EGRET
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GLAST Science Simulated All Sky Map
Virgo Region (E gt 1 GeV)
gt many science objectives
One-Year All-Sky Map (E gt 100 MeV)
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One Year Point Source Catalog
3EG catalog
EGRET 3rd Catalog 271 sources
Expected GLAST LAT 1st Catalog 10,000 sources
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GLAST Science Topics

• Active Galactic Nuclei
• Isotropic Diffuse Background Radiation
• Cosmic Ray Production
• Identify sites and mechanisms
• Endpoints of Stellar Evolution
• Neutron Stars/Pulsars
• Black Holes
• Unidentified Gamma-ray Sources
• Dark Matter
• Solar Physics
• Gamma-Ray Bursts
• DISCOVERY!

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Science capabilities - sensitivity
large field-of-view
200 ? bursts per year ? prompt emission
sampled to gt 20 µs AGN flares gt 2 mn ? time
profile ?E/E ? physics of jets and
acceleration ? bursts delayed emission all
3EG sources 80 new in 2 days ? periodicity
searches (pulsars X-ray binaries) ? pulsar
beam emission vs. luminosity, age, B 104
sources in 1-yr survey ? AGN logN-logS, duty
cycle, emission vs. type, redshift,
aspect angle ? extragalactic background light
(? IR-opt) ? new ? sources (µQSO, ext.
galaxies, clusters)
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International Collaboration

• access to X-ray, MeV, and TeV observatories by
  collaboration
• for multi-wavelength observations
• mirror data site in Europe

100 collaborators from 28 institutions
CAL
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GLAST LAT Project Recent Upcoming Milestones

• NRC Decadal Astronomy Astrophysics Review ranks
  GLAST highest priority moderate-size space
  mission for next decade Sept 2000
• 1st joint DOE-NASA Pre-baseline Lehman Review
  of GLAST LAT Project Feb 13-15, 2001
• Launch date delayed 6 months due to NASA Mission
  funding issues, March 19, 2001 launch now March
  2006
• NASA Independent Assessment Review of GLAST
  Mission completed in December 2000 recommended
  NASA funding augmentation for mission
• NASA Headquarters approves IA-recommended mission
  funding profile (consistent with March 2006
  launch) including contingency funds to procure
  Delta II-H (heavy) launch vehicle if needed
  April 10, 2001
• LAT Project preparing for DOE-NASA Baseline/PDR
  Review this October
• Preparing for Balloon Flight of Engineering
  Model, Summer 2001
• GLAST LAT Collaboration meeting scheduled for
  August 1-2, 2001 at Stanford University

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Status of International Arrangements

• 2 International Agreements and 4 MoAs still being
  negotiated complete drafts exist for all
  agreements 3 MoAs signed (Japan Sweden UCSC)
• International Agreements delayed because
  Implementing Arrangement and MoU between DOE and
  NASA not in place
• International agreements needed with CNES (French
  Space Agency) and ASI (Italian Space Agency)
• Lack of International Agreement and MoA with
  France (CNES) has impacted calorimeter schedule
  French team from CEA/Saclay and IN2P3, but
  majority of funding from CNES working issues
  night day

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GLAST LAT Organization
Collaboration Science Team
E/PO L. Cominsky, SSU
Principal Investigator P. Michelson, SU
SSAC N. Gehrels, GSFC
Instrument Scientist S. Ritz, GSFC
Project Manager W. Althouse, SLAC
Instrument Design Team T. Kamae, SLAC
System Engineer T. Thurston, SLAC
Project Controls T. Boysen, SLAC
Integration Test M. Nordby, SLAC
Electronics DAQ G. Haller, SLAC
Performance Safety Assurance D. Marsh, SLAC
Mech. Systems M. Nordby, SLAC
Sci. Software R. Dubois, SLAC
IOC S. Williams, SU
CAL N. Johnson, NRL France, Sweden
TKR R. Johnson, UCSC SLAC, Italy, Japan
ACD J. Ormes, GSFC
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Collaboration Organization

• Senior Scientist Advisory Committee
• N. Gehrels, Chair
• P. Michelson, PI/Spokesperson
• G. Barbiellini, Italy
• R. Bellazzini, Italy
• E. Bloom, U.S.
• T. Burnett, U.S.
• P. Carlson, Sweden
• A. Djannati-Atai, France
• R. Dubois, U.S.
• Advises PI/Spokesperson on science issues and
  science organization of collaboration
• Implements collaboration membership policy and
  publication policy
• Meets quarterly

• I. Grenier, France
• N. Johnson, U.S.
• R. Johnson, U.S.
• T. Kamae, Japan
• J. Ormes, U.S.
• S. Ritz, U.S.
• H. Sadrozinski, U.S.
• D. Thompson, U.S.
• K. Wood, U.S.

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Collaboration Organization

• Instrument Design Team
• Chaired by Instrument Technical Manager, T. Kamae
• Deputy Chairs R. Bellazzini (Italy), E. Bloom
  (US), J. Paul (France)
• Reports to Project Manager, W. Althouse
• Forum for exchange of information between
  subsystems to maintain coordinated design
  resolve issues or refer to IPO for resolution
• Membership includes all subsystem managers key
  system engineering personnel
• IDT members obliged to attend IDT meetings
  meetings open to the Collaboration
• Weekly video conference meetings

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GLAST Mission Science Working Group

• Advises the GLAST Mission Project on matters
  related to the scientific development of the
  GLAST mission
• Jonathan Ormes, Chair, GLAST Mission Project
  Scientist
• Guido Barbiellini, Italy
• Elliott Bloom, USA
• Patrizia Caraveo, Italy
• Charles Dermer, (IDS), USA
• Brenda Dingus, (IDS), USA
• Neil Gehrels, Deputy Proj. Scientist, USA
• Isabelle Grenier, France
• Neil Johnson, USA
• Tuneyoshi Kamae, Japan
• Giselher Lichti, (GBM), Germany

Charles Meegan, (PI-GBM), USA Peter Michelson,
(PI-LAT), USA M. Pohl, (IDS), Germany David
Thompson, USA Steve Thorsett, (IDS), USA Steve
Ritz, Deputy Project Sci., USA Lynn Cominsky,
E/PO Don Kniffen, ex officio, Program Scientist
GLAST LAT Collaboration Members
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GLAST Large Area Telescope (LAT) Design
Instrument
Pair-conversion telescope
Instrument must measure the direction, energy,
and arrival time of high-energy photons (20 MeV -
gt300 GeV)

• energy resolution requires calorimeter depth
  sufficient to measure buildup of EM shower.
• calorimeter segmentation useful for
  resolution
• background rejection

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Large Area Telescope (LAT) Design Overview
Instrument
16 towers ? modularity height/width 0.4 ?
large field-of-view Si-strip detectors total
of 106 ch. hodoscopic CsI crystal array
? cosmic-ray rejection ? shower
leakage correction shower max
contained lt 100 GeV segmented plastic
scintillator ? minimize self-veto

Tracker
Calorimeter
Anticoincidence Detector Shield
3000 kg, 650 W (allocation) 1.75 m ? 1.75 m ?
1.0 m 20 MeV 300 GeV
Flight Hardware Spares 16 Tracker Flight
Modules 2 spares 16 Calorimeter Modules 2
spares 1 Flight Anticoincidence Detector Data
Acquisition Electronics Flight Software
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GLAST Large Area Telescope (LAT) Design
Tracker Modules
Si-strip detectors fine pitch 228 mm, high
efficiency 12 front tracking planes (x,y) 3
x 12 0.45 Xo reduce multiple
scattering 4 back tracking planes (x,y)
18 x 4 0.72 Xo increase
sensitivity gt 1 GeV
e
e
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GLAST Large Area Telescope (LAT) Design
Calorimeter Modules
Hodoscopic Imaging Array of CsI crystals
8.5 rl depth PIN photodiode readout from both
ends 2 ch/xtal x 96 xtals/mod 2,944 ch
segmentation allows pattern
recognition (imaging) and
leakage correction
Mechanical Prototype of Carbon Cell Design
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GLAST Large Area Telescope (LAT) Design
Anticoincidence Shield
Segmented, plastic scintillator tile array
high efficiency, low-noise, hermetic
segment ACD sufficiently and
only veto event if a track points to
hit tile
ACD tile readout with Wavelength Shifting Fiber
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Detector Performance Verified in Detailed Beam
Tests
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PSF measured for Flight-scale Prototype Tracker
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Energy Response measured for Flight-scale
Prototype Calorimeter Module
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The PSF as a function of the reconstructed energy
for data and Monte Carlo simulation. The expected
1/E behavior is clearly seen. As the photon
energy increases, multiple scattering becomes
less important and the PSF decreases. At high
energies the point spread function is dominated
by the finite spatial resolution of the silicon
detectors (60 microns). The thick radiators at
the back of the tracker widen the point spread
function by slightly more than a factor of 2.
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Because of the calorimeter depth, the shower
maximum is contained up to 50 GeV at normal
incidence. However, above a few GeV, a large
amount of energy leaks out the back of the
calorimeter, and the total energy measured is
systematically less than the incident energy. We
have employed two techniques to correct for the
shower leakage. We show the raw and reconstructed
energy for 20 GeV incident positrons. The
resolution of the raw distribution is around 7,
while the reconstructed resolution is less than
4 by the correlation method and about 5 by
profile fitting. The reconstruction method
applied to Monte Carlo simulated data yields an
energy resolution of 3, suggesting that some
uncertainties remain in our calibration of beam
test data.
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Schedule