Fermi (GLAST)
Gamma-ray Space Telescope
Mission Overview
Michael Stamatikos†
NASA Postdoctoral Fellow
Goddard Space Flight Center (GSFC)
Astrophysics Science Division (ASD)
Astroparticle Physics Laboratory (Code 661)
Michael.Stamatikos-1@nasa.gov
†On
behalf of the Fermi Large Area Telescope (LAT)
Collaboration and Fermi Mission
Novel Searches for Dark Matter Workshop
Center for Cosmology and AstroParticle
Physics (CCAPP)
The Ohio State University (OSU)
November 17, 2008
The Gamma-ray Large Area Space
Telescope (GLAST) was renamed
Fermi by NASA on August 26, 2008:
http://fermi.gsfc.nasa.gov/
“Enrico Fermi (1901-1954) was an
Italian physicist who immigrated to
the United States. He was the first to
suggest a viable mechanism for
astrophysical particle acceleration.
This work is the foundation for our
understanding of many types of
sources to be studied by NASA’s
Fermi Gamma-ray Space Telescope,
formerly known as GLAST. ”
Why Study g-rays?
Fermi-LAT
Gamma-ray
1 year
SkySimulated
Seen by
EGRET
Observation
on CGRO
red:
green:
blue:
0.1-0.4 GeV
0.4-1.6 GeV
>1.6 GeV
Gamma-ray sky is dynamic,
changing on timescales from
milliseconds to years, revealing
high-energy processes and exotic
cosmic phenomena.
> 2000 AGNs
Possibilities
blazars and radiogal = f(q,z)
evolution z < 5
Sag A*
starburst galaxies
galaxy clusters
measure EBL
unIDs
10-50 GRB/year
GeV afterglow
spectra to high energy
g-ray binaries
Dark Matter
neutralino lines
sub-halo clumps
Pulsar winds
m-quasar jets
Pulsars
Cosmic rays and clouds
acceleration in Supernova remnants
OB associations
propagation (Milky Way, M31, LMC, SMC)
Interstellar mass tracers in galaxies
emission from radio and X-ray pulsars
blind searches for new Gemingas
magnetospheric physics
pulsar wind nebulae
Fermi Key Features
•
Two Fermi instruments:
Large Area Telescope (LAT)
– LAT:
• high energy (20 MeV – >300 GeV)
– GBM:
• low energy (8 keV – 30 MeV)
~2.5 sr
 8 sr
•
•
•
Spacecraft Partner:
General Dynamics
Fermi Gamma-ray Burst Monitor
(GBM)
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 - 100 GeV
Large leap in all key capabilities, transforming our knowledge of the gammaray universe. Great discovery potential.
The Fermi Observatory
LAT
GBM
12 Sodium
Iodide (NaI)
Scintillation
Detectors (8
keV – 1
MeV)
GBM
2 Bismuth
Germanate
(BGO)
detectors (0.15
- 30 MeV)
Fermi Launched from Cape Canaveral Air Force
Station on June 11, 2008 @ 12:05 PM EDT
Fermi MISSION ELEMENTS
•
•
GPS
msec
Large Area Telescope
& GBM
DELTA
7920H
-
• Telemetry 1 kbps
•
Fermi Spacecraft
TDRSS SN
S & Ku
•
•
S
•
GN
•
Schedules
Mission Operations
Center (MOC)
Fermi Science
Support Center
(FSFC)
Schedules
GRB
Coordinates Network
Alerts
Data, Command Loads
LAT Instrument
Science
Operations Center
(Stanford/SLAC)
White Sands
HEASARC
GBM Instrument
Operations Center
Huntsville)
Circular orbit, 565 km altitude (96 min period), 25.6 deg inclination.
Communications: Science data link via TDRSS Ku-band, average data rate 1.2 Mbps.
S-band via TDRSS and ground stations
Fermi LAT Collaboration
•
•
•
•
•
France
Principal Investigator:
– CNRS/IN2P3, CEA/Saclay
Peter Michelson (Stanford University)
Italy
– INFN, ASI, INAF
~270 Members
Japan
(~90 Affiliated Scientists, 37 Postdocs,
– Hiroshima University
and 48 Graduate Students)
– ISAS/JAXA
– RIKEN
construction managed by
– Tokyo Institute of Technology
Stanford Linear Accelerator Center
Sweden
(SLAC), Stanford University
– Royal Institute of Technology (KTH)
– Stockholm University
United States
– Stanford University (SLAC and HEPL/Physics)
– University of California at Santa Cruz - Santa Cruz Institute for Particle
Physics
– Goddard Space Flight Center
– Naval Research Laboratory
– Sonoma State University
– Ohio State University
– University of Washington
Fermi LAT Overview: Overall Design
Overall LAT Design:
•4x4 array of identical towers
•3000 kg, 650 W (allocation)
•1.8 m  1.8 m  1.0 m
•20 MeV – >300 GeV
Anticoincidence Detector:
• 89 scintillator tiles
• First step in reduction of large charged cosmic ray
background
• Segmentation reduces self veto at high energy
g
Thermal Blanket:
• And micro-meteorite shield
Precision Si-strip Tracker:
Measures incident gamma direction
18 XY tracking planes. 228 mm pitch.
High efficiency. Good position resolution
12 x 0.03 X0 front end => reduce multiple
scattering.
4 x 0.18 X0 back-end => increase
sensitivity >1GeV
Hodoscopic CsI Calorimeter:
• Segmented array of 1536 CsI(Tl) crystals
• 8.5 X0: shower max contained <100 GeV
• Measures the incident gamma energy
• Rejects cosmic ray backgrounds
e+
e–
Electronics System:
• Includes flexible, highly-efficient,
multi-level trigger
LAT Construction: An International Effort
Integration &
Data System: US
ACD: US
Tracker: US, Italy, Japan
Calorimeter: US,
France, Sweden
Years
Ang. Res.
Aeff Ω
Ang. Res. (10 GeV) Eng. Rng. (GeV)
(100 MeV)
(cm2 sr)
# g-rays
1.4 × 106
EGRET
1991–00
5.8°
0.5°
0.03–10
AGILE
2007–
4.7°
0.2°
0.03–50
1,500 4 × 106/yr
Fermi LAT
2008–
3.5°
0.1°
0.02–300
25,000 1 × 108/yr
750
• LAT has already surpassed EGRET and AGILE celestial gamma-ray totals
• Unlike EGRET and AGILE, LAT is an effective All-Sky Monitor
whole sky every ~3 hours
EGRET
AGILE (ASI)
CGRO EGRET
Fermi / LAT
(~96 min)
…. Transient class
Source class
Diffuse class
Thin Front (dashed)
Thick Back (solid)
Total (dotted)
LAT’s First Light!
Four days of all-sky survey Fermi engineering data, already comparable to
18 month EGRET Sky map!
GBM Collaboration
National Space Science & Technology Center
University of Alabama
in Huntsville
NASA
Marshall Space Flight Center
Max-Planck-Institut für
extraterrestrische Physik
Charles Meegan (PI)
Jochen Greiner (Co-PI)
GBM On-board Trigger Algorithm
• Four energy ranges: 25-50, 50-300, >100, >300
(keV)
• Eleven integration times: 16 ms – 8 s.
• Two timing phases
• Threshold of 4.5 sigma for 50-300 keV, 64 ms – 4 s
• Background rate 50-300 keV is ~320 counts/s
• Flux threshold for 1 s burst, 50-300 keV: ~0.75
photons/cm2/s
• Prediction of 200 bursts/year with BATSE-like
trigger
GBM Spots GRBs Daily
+90
–180
+180
•
•
•
•
–90
31 GRBs seen in first month of operations
Activation phase complete; all working well
Sensitivity as predicted
GRB locations within a few degrees of Swift calculations
Data Release plan and operations
•
•
•
•
First Year observations - Sky Survey
– Initial on-orbit checkout (60 days), then first year of observations will be a
sky survey.
– Re-points 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 catalog 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 http://glast.gsfc.nasa.gov/ssc/data/policy/ for more details.
What Next for Fermi?
• The Fermi Gamma-ray Space Telescope is fully operational.
• In just a few days, the Large Area Telescope (LAT) corroborated many
of the great discoveries of EGRET and AGILE; now finding new
sources as well.
• We have only scratched the surface of what the Fermi Gamma-ray
Space Telescope can do. The gamma-ray sky is changing every day,
so there is always something new to learn about the extreme Universe.
• Some results from both the GBM and the LAT are starting to be made
public through the Fermi Science Support Center.
• Fermi science teams are cooperating with many other missions and
observatories to maximize the scientific return.
• Undoubtedly, the most exciting is yet to come as we have just started
the all-sky survey phase and with time probe deeper and deeper into
the high-energy Universe.
• Follow the latest news at the Project Scientist’s blog,
http://blogs.nasa.gov/cm/blog/GLAST.