GLAST CDR

1
Overview of the GLAST Mission GRB Capabilities
Elliott Bloom SLAC - KIPAC Stanford
University Representing the GLAST LAT
Collaboration 2nd Informal Zwicky Workshop UCB
May 25, 2005
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Why study gs?

• Gamma rays carry a wealth of information
• g rays offer a direct view into Natures largest
  accelerators.
• the Universe is mainly transparent to g rays (lt
  20 GeV) can probe cosmological volumes. Any
  opacity is energy-dependent.
• conversely, g rays readily interact in
  detectors, with a clear signature.
• g rays are neutral no complications due to
  magnetic fields. Point directly back to
  sources, etc.
• Two GLAST instruments
• LAT 20 MeV gt300 GeV
• GBM 10 keV 25 MeV
• Launch 2007
• 5-year mission (10-year goal)

Large Area Telescope (LAT)
spacecraft partner
GLAST Burst Monitor (GBM)
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GLAST is an International Mission

• NASA - DoE Cooperation on LAT
• LAT is being built by an international team (PI
  P. Michelson)
• Stanford University (SLAC HEPL, Physics)
• Goddard Space Flight Center
• Naval Research Laboratory
• University of California, Santa Cruz
• University of Washington
• Ohio State University
• CEA/Saclay IN2P3 (France)
• ASI INFN (Italy)
• Hiroshima University, ISAS, RIKEN (Japan)
• Royal Inst. of Technology Stockholm Univ.
  (Sweden)
• GBM is being built by US and Germany (PI C.
  Meegan)
• MPE, Garching (Germany)
• Marshall Space Flight Center
• Spacecraft and integration - Spectrum Astro
• Mission Management NASA/GSFC

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The GLAST LAT Instrument
Systems work together to identify and measure the
cosmic gamma ray flux with energy 0.02 to gt 300
GeV.
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GLAST LAT High Energy Capabilities

• Huge FOV (20 of sky)
• Broadband (4 decades in energy, including
  unexplored region gt 10 GeV)
• Unprecedented PSF for gamma rays (factor gt 3
  better than EGRET for Egt1 GeV)
• Large effective area (9x larger than EGRET _at_ 1
  GeV)
• Results in factor gt 30-100 improvement in
  sensitivity
• much smaller deadtime per event (25 m sec ?
  factor 4,000 better than EGRET)
• No expendables long mission without
  degradation

6
GLAST LAT Technical Status
5 Trackers _at_ SLAC. 80m2 of silicon detectors in
hand.
10 CAL modules at SLAC.
ACD flight structure with flight tiles being
integrated. Integration is nearly complete.
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GLAST addresses a broad science menu

• Systems with super massive black holes
  relativistic jets
• Gamma-ray bursts (GRBs)
• Pulsars
• Solar physics
• Origin of Cosmic Rays
• Probing the era of galaxy formation
• Solving the mystery of the high-energy
  unidentified sources
• Discovery! Particle Dark Matter? Other relics
  from the Big Bang?
• Limits on extra dimensions. New source
  classes

GLAST draws the interest of both the High Energy
Particle Physics and High Energy Astrophysics
communities.
Selected by the NAS in their 2000 decadal study
as the highest priority mid-sized mission
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High energy source sensitivity all-sky scan mode
100 sec
During the all-sky survey, GLAST will have
sufficient sensitivity after O(1) day to detect
(5s) the weakest EGRET sources.
EGRET Fluxes

• - GRB940217 (100sec)
• - PKS 1622-287 flare
• - 3C279 flare
• - Vela Pulsar
• - Crab Pulsar
• - 3EG 202040 (SNR g Cygni?)
• - 3EG 183559
• - 3C279 lowest 5s detection
• - 3EG 1911-2000 (AGN)
• - Mrk 421
• - Weakest 5s EGRET source

1 orbit
1 day
zenith-pointed
rocking all-sky scan alternating orbits point
above/below the orbit plane
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3rd EGRET Catalog
GLAST Survey 10,000 sources (2 years)
GLAST Survey 300 sources (2 days)
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Gamma Ray Bursts
Highest-energy emission from bursts is intriguing
EGRET detected a 20 GeV photon 75 minutes after
the start of a burst
Milagrito evidence for TeV emission from GRB
970417 ApJ 533(2000)533.
Hurley et al., 1994
Future Prospects GLAST will provide definitive
information about the high energy behavior of
bursts LAT and GBM together will measure
emission over gt7 decades of energy. There likely
will be additional TeV burst detections.
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GRBs and Instrument Deadtime
Distribution for the 20th brightest burst in a
year (Norris et al)
Time between consecutive arriving photons
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Roles of the GBM

• 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)
• GLAST observatory provides burst alerts to the
  ground.

Simulated GBM and LAT response to time-integrated
flux from bright GRB 940217 Spectral model
parameters from CGRO wide-band fit 1 NaI (14º)
and 1 BGO (30º)
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GRB941017

• Gonzalez et al., published in Nature

Compare data from EGRET and BATSE Distinct
high-energy component has different time
behavior. What is the high-energy break and total
luminosity? GLAST data, LAT GBM, will allow
detailed studies
80-113 sec 113-211 sec
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Key GBM Science Performance Requirements Summary
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GBM Collaboration
National Space Science Technology Center
University of Alabama in Huntsville
NASA Marshall Space Flight Center
Max-Planck-Institut für extraterrestrische Physik
Giselher Lichti (Co-PI) Andreas von
Keinlin Volker Schönfelder Roland Diehl Jochen
Greiner Helmut Steinle
Michael Briggs William Paciesas Robert
Preece Narayana Bhat Marc Kippen (LANL)
Charles Meegan (PI) Gerald Fishman Chryssa
Kouveliotou Robert Wilson
On-board processing, flight software, systems
engineering, analysis software, and management
Detectors, power supplies, calibration, and
analysis software
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Burst Handling

• Upon detection of a GRB, GLAST can take two
  DIFFERENT kinds of actions
• alerts to the ground
• GBM and LAT issue alerts independently.
• The alert response time shall be less than 7
  seconds with a goal of less than 4 seconds from
  the time of spacecraft receipt of GRB
  notification from GBM or LAT to delivery to the
  Gamma-ray Coordinates Network (GCN) computer for
  80 of all GRBs detected by the GBM or LAT.
• autonomous repoint to follow burst
• both GBM and LAT can generate a repoint request.
• GBM will probably detect more bursts than LAT.
  However, if LAT detects a burst, it will probably
  provide a better localization of the burst
  position
• therefore, GBM repoint request routed through
  LAT, which either passes on the GBM request or
  sends LATs position.
• The spacecraft shall be capable of slewing the
  observatory Z axis through an angle of 75
  degrees in less than 10 minutes 100 of the time
  under 4 reaction wheel (RWA) control and 75 of
  the time under 3 RWA control (single RWA failure)
  accounting for slew constraints (e.g. yaw
  flips), with a goal of less than 5 minutes, while
  maintaining all applicable attitude
  constraints.
• alerts will happen much more frequently than
  repoint requests

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Extra Slides
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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 Operations Center
White Sands
Schedules
HEASARC GSFC
Archive
Mission Operations Center (MOC)
GLAST Science Support Center
Schedules
GBM Instrument Operations Center
GRB Coordinates Network
Alerts
Data, Command Loads
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Science Mission Elements

• Science Working Group (chair, S. Ritz, Project
  Scientist)
• membership includes Interdisciplinary Scientists,
  instrument team PIs and instrument team
  representatives
• bi-monthly telecons and bi-annual sit-down
  meetings, along with science symposia to engage
  the community.
• Users Committee (chair J. Grindlay)
• independent of the SWG. External review/feedback
  on science tools planning and progress.
• includes members from both the astrophysics and
  high-energy particle physics communities who are
  likely users of GLAST data.
• GLAST Science Support Center (GSSC)
• located at Goddard. Supports guest observer
  program, provides training workshops, provides
  data and software to community, archives to
  HEASARC, joint software development with
  Instrument Teams.

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Dramatic Improvement in PSF over EGRET
EGRET source position error circles are 0.5,
resulting in counterpart confusion. GLAST will
provide much more accurate positions, with 30
arcsec - 5 arcmin localizations, depending on
brightness.
Cygnus region (15x15 deg)
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All-Sky Survey
GLAST Large Area Telescope (LAT)
LAT will view all regions of the sky for 25
minutes every 3 hours.
Burst Monitor (GBM)
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All-Sky Survey
GLAST Large Area Telescope (LAT)
LAT will view all regions of the sky for 25
minutes every 3 hours.
Burst Monitor (GBM)
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Key LAT Science Performance Requirements Summary
Parameter SRD Value Present Design Value
Peak Effective Area (in range 1-10 GeV) gt8000 cm2 10,000 cm2 at 10 GeV
Energy Resolution 100 MeV on-axis lt10 9
Energy Resolution 10 GeV on-axis lt10 8
Energy Resolution 10-300 GeV on-axis lt20 lt15
Energy Resolution 10-300 GeV off-axis (gt60º) lt6 lt4.5
PSF 68 100 MeV on-axis lt3.5 3.37 (front), 4.64 (total)
PSF 68 10 GeV on-axis lt0.15 0.086 (front), 0.115 (total)
PSF 95/68 ratio lt3 2.1 front, 2.6 back (100 MeV)
PSF 55º/normal ratio lt1.7 1.6
Field of View gt2sr 2.4 sr
Background rejection (Egt100 MeV) lt10 diffuse 6 diffuse (adjustable)
Point Source Sensitivity(gt100MeV) lt6x10-9 cm-2s-1 3x10-9 cm-2s-1
Source Location Determination lt0.5 arcmin lt0.4 arcmin (ignoring BACK info)
GRB localization lt10 arcmin 5 arcmin (ignoring BACK info)

• LAT meets all requirements, and many analysis
  improvements are underway.

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GBM Status

• Flight detectors and power supply in assembly in
  Germany
• Data Processing Unit delivered to MSFC for IT