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GLAST Mission: Status and Science Opportunities Peter F. Michelson Stanford University

Gamma-ray Large Area Space Telescope. GLAST Mission: Status and Science Opportunities Peter F. Michelson Stanford University peterm@stanford.edu. Outline. GLAST: An International Science Mission Large Area Telescope (LAT) GLAST Burst Monitor (GBM) Mission Operations Plan

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GLAST Mission: Status and Science Opportunities Peter F. Michelson Stanford University

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  1. Gamma-ray Large Area Space Telescope GLAST Mission: Status and Science Opportunities Peter F. Michelson Stanford University peterm@stanford.edu

  2. Outline • GLAST: An International Science Mission • Large Area Telescope (LAT) • GLAST Burst Monitor (GBM) • Mission Operations Plan • highlights of science opportunities • schedule highlights

  3. The GLAST Observatory Large Area Telescope (LAT) GLAST Burst Monitor (GBM) two GLAST instruments: LAT: 20 MeV – >300 GeV GBM: 10 keV – 25 MeV

  4. GLAST is an International Mission Sweden France Italy Japan Germany USA NASA - DoE Partnership on LAT LAT is being built by an international team (PI: P. Michelson, Stanford University) Si Tracker: UCSC, Italy, Japan, Stanford/SLAC CsI Calorimeter: NRL, France, Sweden Anticoincidence: GSFC Data Acquisition System: Stanford/SLAC, NRL GBM is being built by US and Germany (PI: C. Meegan, NASA/MSFC) Detectors: MPE Data Acquisition System: MSFC Spacecraft and integration - Spectrum Astro Mission Management: NASA/GSFC ( K. Grady, Project Manager; S. Ritz, Project Scientist)

  5. LAT: experimental technique Energy loss mechanisms:  Pair-Conversion Telescope anticoincidence shield conversion foil particle tracking detectors e– • calorimeter • (energy measurement) e+ • instrument must measure the direction, energy, and arrivaltime of high • energy photons (from approximately 20 MeV to greater than 300 GeV): • - photon interactions with matter in GLAST • energy range dominated by pair conversion: • determinephoton direction • clear signature for background rejection - limitations on angular resolution (PSF) low E: multiple scattering => many thin layers high E: hit precision & lever arm • must detect -rays with high efficiency and reject the much larger (~104:1) flux of background cosmic-rays, etc.; • energy resolution requires calorimeter of sufficient depth to measure buildup of the EM shower. Segmentation useful for resolution and background rejection.

  6. Overview of LAT  Tracker ACD [surrounds 4x4 array of TKR towers] e– e+ Calorimeter • Precision Si-strip Tracker (TKR)18 XY tracking planes. Single-sided silicon strip detectors (228 mm pitch) Measure the photon direction; gamma ID. • Hodoscopic CsI Calorimeter(CAL)Array of 1536 CsI(Tl) crystals in 8 layers. Measure the photon energy; image the shower. • Segmented Anticoincidence Detector (ACD)89 plastic scintillator tiles. Reject background of charged cosmic rays; segmentation removes self-veto effects at high energy. • Electronics SystemIncludes 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.

  7. Huge FOV (~20% of sky) Broadband (4 decades in energy, including unexplored region > 10 GeV) Unprecedented PSF for gamma rays (factor > 3 better than EGRET for E>1 GeV) Large effective area (factor > 4 better than EGRET) Results in factor > 30-100 improvement in sensitivity No expendables long mission without degradation GLAST LAT High Energy Capabilities

  8. 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 2020+40 (SNR g Cygni?) • - 3EG 1835+59 • - 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

  9. GBM Detector (12) Sodium Iodide (NaI) Scintillation Detectors Bismuth Germanate (BGO) Scintillation Detector LAT Major Purposes • Provide low-energy spectral coverage in the typical GRB energy regime over a wide FoV (10 keV – 1 MeV) • Provide rough burst locations over a wide FoV Major Purpose • Provide high-energy spectral coverage (150 keV – 25 MeV) to overlap LAT range over a wide FoV

  10. Roles of the GBM provides spectra for bursts from 10 keV to 25 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)

  11. 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 Mission Operations Center (MOC) GLAST Science Support Center HEASARC GSFC Archive Schedules GRB Coordinates Network GBM Instrument Operations Center Alerts Data, Command Loads

  12. The GLAST Science Support Center • located in Goddard’s Laboratory for High Energy Astrophysics • SSC responsible for: • supporting the guest investigator program • the mission timeline (includes support for TOOs, commands) • providing data & analysis software to the scientific community • archiving data & software in the HEASARC • supporting (logistically & scientifically) the Project Scientist, the Science Working Group, and the Users’ Committee • instrument teams and SSC define and develop the analysis software together • instrument teams manage the software development, but SSC staff assists

  13. GLAST addresses a broad science menu • Systems with supermassive 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? • Testing Lorentz invariance. New source classes GLAST draws the interest of both the High Energy Particle Physics and High Energy Astrophysics communities.

  14. Features of the gamma-ray sky field of view, and the ability to repoint, important for study of transients. diffuse extra-galactic background (flux ~ 1.5x10-5 cm-2s-1sr-1) galactic diffuse (flux ~O(100) times larger) high latitude (extra-galactic) point sources (typical flux from EGRET sources O(10-7 - 10-6) cm-2s-1 galactic sources (pulsars, un-ID’d) EGRET all-sky survey (E>100 MeV) An essential characteristic: VARIABILITY in time!

  15. 3rd EGRET Catalog pulsars AGN - blazars LMC unidentified GLAST Survey: ~10,000 sources (2 years) GLAST Survey: ~300 sources (2 days)

  16. Constraints on extragalactic background light (EBL) from g-ray blazars Salamon & Stecker, ApJ 493, 547 (1998) Chen & Ritz, ApJ (2000) No significant attenuation below 10 GeV photons with E>10 GeV are attenuated by the diffuse field of UV-Optical-IR extragalactic background light (EBL) g + g e+ + e- a dominant factor in determining the EBL is the time of galaxy formation opaque

  17. Unidentified Sources 172 of the 271 sources in the EGRET 3rd catalog are “unidentified” 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)

  18. Gamma-Ray Bursts GRBs are now confirmed to be at cosmological distances. The question persists :What are they?? EGRET detected very high energy emission associated with bursts, including a 20 GeV photon ~75 minutes after the start of a burst: 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 >7 decades of energy.

  19. GRBs and instrument deadtime LAT will open a wide window on the study of the high energy behavior of bursts. Distribution for the 20th brightest burst in a year (Norris et al) Time between consecutive arriving photons

  20. GRB 941017 -18 to 14 sec 14 to 47 sec 47 to 80 sec 80-113 sec 113-211 sec Compare data from EGRET and BATSE: Distinct high-energy component has different time behavior! What is the high-energy break and total luminosity? Need GLAST data! recent analysis by Gonzalez, et al.

  21. GLAST Master Schedule Launch: February 2007 First flight hardware deliveries to SLAC for I&T: August 2004 LAT ready for Environmental Test: July 2005 GBM I&T starts: September 2004 Observatory I&T starts: December 2005

  22. ` GLAST: Exploring Nature’s Highest Energy Processes launch: February 2007

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