1. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 1 Gamma-ray Large Area Space Telescope OSU and GLAST Richard E. Hughes, The Ohio State University, The GLAST-LAT Collaboration. Department of Energy Review 28-Sep-2006

2. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 2 What is GLAST? Two GLAST instruments: LAT: 20 MeV – >300 GeV GBM: 10 keV – 25 MeV Launch: 2007 GLAST Large Area Telescope (LAT) Burst Monitor (GBM) GLAST will map the universe in gamma rays Gamma-ray Large Area Space Telescope

3. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 3 GLAST LAT Collaboration United States l California State University at Sonoma l University of California at Santa Cruz - Santa Cruz Institute of Particle Physics l Goddard Space Flight Center – Laboratory for High Energy Astrophysics l Naval Research Laboratory l The Ohio State University l Stanford University (SLAC and HEPL/Physics) l University of Washington l Washington University, St. Louis France l IN2P3, CEA/Saclay Italy l INFN, ASI Japanese GLAST Collaboration l Hiroshima University l ISAS, RIKEN Swedish GLAST Collaboration l Royal Institute of Technology (KTH) l Stockholm University PI: Peter Michelson PI: Peter Michelson (Stanford & SLAC) ~225 Members (including ~80 Affiliated Scientists, plus 23 Postdocs, and 32 Graduate Students) Cooperation between NASA and DOE, with key international contributions from France, Italy, Japan and Sweden. Managed at Stanford Linear Accelerator Center (SLAC).

4. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 4 EGRET (>100 MeV) Simulated LAT (>100 MeV, 1 yr) Simulated LAT (>1 GeV, 1 yr) The Gamma-Ray Sky l Comparing EGRET to GLAST:  Illustrating the anticipated improvement in our knowledge of the sky

5. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 5 Why study  ’s? Gamma rays:  Source:   rays do not interact much at their source: they offer a direct view into Nature’s largest accelerators.  the Universe is mainly transparent to  rays: can probe cosmological volumes. Any opacity is energy- dependent.   rays are neutral: no complications due to magnetic fields. Point directly back to sources, etc.  Detection:   rays readily interact  Very clear signature.  Good probe for new physics!  Decays of possible dark matter particles  Tests of fundamental physics (lorentz invariance, etc) GLAST Large Area Telescope (LAT) Burst Monitor (GBM) Opacity (Salamon & Stecker, 1998) No significant attenuation below ~10 GeV. opaque only e -   of the original source flux reaches us

6. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 6 GLAST will have a very broad menu that includes: l Systems with supermassive black holes l Gamma-ray bursts (GRBs) l Pulsars l Solar physics l Origin of Cosmic Rays l Probing the era of galaxy formation l Discovery! Particle Dark Matter? Hawking radiation from primordial black holes? Other relics from the Big Bang? Testing Lorentz invariance. New source classes. Huge increment in capabilities. GLAST draws the interest of both the the High Energy Particle Physics and High Energy Astrophysics communities. GLAST Science

7. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 7 GLAST LAT Overview: Overall Design e+e+ e–e–  Precision Si-strip Tracker: Detectors and converters arranged in 18 x-y tracking planes Measures incident gamma direction Electronics System: Includes flexible, highly-efficient, multi-level trigger Hodoscopic CsI Calorimeter: Segmented array of CsI crystals Measures the incident gamma energy Rejects cosmic ray backgrounds Anticoincidence Detector: Highly efficient segmented scintillator tiles First step in reduction of large charged cosmic ray background Segmentation reduces self veto at high energy 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 Thermal Blanket: And micro-meteorite shield

8. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 8 Cosmic Rays in the LAT: The Movie Muons taken during Integration and Testing with the full LAT

9. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 9 2005-6 OSU Contributions to GLAST l DAQ Testing (Winer)  Code Development (EbfWriter package)  Using GLEAM (GLAST Gen/Sim) to create data sample  Timing Synchronization and Stress Test (e.g. DAQ rates)  Spacecraft Information data stream l Filtering (Hughes,Sander,Smith)  Port of Onboard Filter to Ground Software environment  Development of Filter for Calorimeter Calibration  Development of Filter for Tracker Alignment  Flight software development l Onboard Science (Kuehn, Smith, Hughes, Winer)  GRB Identification Algorithm l Ground Science  New physics: Tests of Lorentz Invariance (Kuehn)  Search for Dark Matter (Sander)

10. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 10 Producing Data for the TestBed l EbfWriter: Software package designed to format data from GLEAM exactly like the satellite would.  ALSO: produces data files needed by the TestBed EbfWriter Digis OnBoardFilter DAQ/Trigger Testbed: FES Input TDS FilterAlg/Other TDS Code from Flight Software Work By Winer/Hughes

11. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 11 DAQ/Trigger Testbed Tests GLEAM/ EbfWriter CAL/TKR/ACD Files VxWorks Nodes FrontEnd Simulators (FES) TEMs GASU OnBoardFilter Hardware Event Software Event DAQ/Trigger Testbead Compare Predicted vs Observed Samples : Single Particle AllGamma Sample Background Sample Data Challenge 1 Integrity Testing Rate Testing Filter Testing Work by Brian Winer

12. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 12 Front-end Simulator l System uses 9 PC’s  8 PC’s for 16 TEM’s  1 PC for ACD l Data transported to towers via high-speed data link; PCI bridge to local bus on simulator l Data Simulators interface to TEM like CAL and TKR sub- system electronics  CAL and TKR simulator board identical except code in FPGA’s l Can operate TEM or LAT with data generated from simulations Front-end Simulator (FES) Board

13. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 13 TestBed at SLAC TEMs GASU Racks with PCs for driving FES boards.

14. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 14 Example result from Testbed Runs Generated 4.5 Million background events for running through the testbed. * Check DAQ system for data corruption. * Measure expected deadtime in DAQ system. Deadtime was found to be a few percent as expected. Black Points: Data captured at the output of the testbed. Red Hist: Expected output predicted by detector sim. Green: Ratio of black points and red histograms…all at 1.0 Work By Brian Winer

15. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 15  Tkr 3-in-a-row  3 x,y planes hit in a row  “workhorse”  - ray trigger  CAL-LO  any log with >100MeV  CAL-HI  > 0 crystals with > 1GeV  indicates a high energy event  CNO  ACD hit with high discriminator signal  Throttle  a tower with a Tkr 3-in-a-row is  shadowed by an ACD hit Level 1 Hardware Triggers (Did anything happen?) Upon L1trigger: all towers read out within 20  s L1 trigger rate ~ Example of photon LAT, producing e+/e- pair, triggering a Tkr 3-in-a-row and depositing energy in certain CAL crystals Combinations of these trigger primitives are used to define a hardware trigger

16. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 16 GLAST Data Rates and OnboardFilter l Downlink rate: 1.2Mbps  Average event size ~3kb (after compression)  Accept rate must be < 400 Hz l Expected background rate after triggering: ~3-4 kHz  CREME96 model (used by NASA, DepDef, commercial satellites)  Contains CNO, albedo, electrons, etc l Hardware trigger vetoes reduce rate by ~30%  Search for cosmics by shadowing of towers by ACD tiles  Reduces “good” gammas by ~3% l Still need to reduce rate by ~factor of 10  Use software filter: OnboardFilter

17. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 17 The OnboardFilter l The onboard filter is software written in C l Runs on the EPU l Purpose  GammaFilter: Reduce overall rate to <400Hz  CNO Filter:  CNO Filter: Select events for calorimeter calibration  AlignmentFilter: Select events for aligning the tracker  OnboardScience: Not strictly part of the filter. Needed to identify specific event types: e.g. GRBs Portion of the Filter Algorithm

18. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 18 Non  Background Composition Counts (Hz) How well does the onboard filter reject the background? Hardware Trigger After Onboard Filter Total Rate ~2600 HzTotal Rate ~370 Hz

19. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 19 Efficiency of the Onboard Filter when the LAT has triggered Black: Gamma Red: Background Log 10 (Energy) MeV Arbitrary Units

20. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 20 CNO Filter:Energy Calibration  Use MIPs to calibrate CAL  MIPs leave a characteristic amount of energy in each layer  MIPs do not shower  We know the real energy of each peak which allows us to convert signal into the real energy carbon peak MeV counts Before CNO filterAfter CNO filter Work by OSU Student Patrick Smith

21. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 21 Tracker alignment filter For intra-tower alignment Use MIP protons passing through 2 towers to find relative alignment of towers Work By OSU Student Aaron Sander

22. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 22 Gamma Ray Bursts l Extemely bright objects, with very large power output, lasting anywhere from seconds to hours  discovered in 1967 by the Vela military satellites, searching for gamma-ray transients l Right: Hubble images of GRB 050709  Detected by HETE  Chandra and Swift observed X-ray afterglow  Hubble observed optical afterglow (5,10, 19, 35 days after burst) l Short vs long bursts:  Short: Merging binaries?  Long: massive star collapsing to black hole?

23. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 23 The GRB finding Algorithm GRB finding algorithms traditionally use temporal information to trigger The LAT’s good pointing ability allows for the use of spatial information in the trigger The algorithm looks for a “large” (improbable) number of photons in a short period of time, in a small region of the sky We are beginning the implementation of the algorithm into the onboard environment now Onboard Science

24. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 24 Triggers & Probabilities Example spatial probability plot GRB photons have “clusters” with high cumulative probability Background photon have “clusters” with low cumulative probability A similar plot exists for the cumulative time probability (we will likely trigger on the sum of both) Work by OSU Student Fred Kuehn

25. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 25 Improving the Onboard Localization Work by OSU Student Patrick Smith

26. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 26 GRBs and Instrument Deadtime Time between consecutive arriving photons Distribution for the 20 brightest bursts in a year (Norris et al) LAT will open a wide window on the study of the high energy behavior of bursts. EGRET deadtime: ~100ms

27. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 27 Using GRBs as a Probe for New Physics Credit: F. Longo; GLAST GRB Science Team Measuring GRB at different redshift can be used as a probe for Lorentz Invariance Violation  Effects arise in some Quantum Gravity Models.  Look for delayed arrival of photons as a function of energy.

28. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 28 Using GRBs as a Probe for New Physics l LAT provides a means to measure the high energy photons and arrival.  System clock: 50 ns l Other observations required to localize and measure redshifts. Norris, Bonnell, Marani, Scargle 1999 20 bright GRBs @1 Gpc w/ QG. Dispersion due to QG. Raw calorimeter energy (log10(MeV)) Time between successive photons (s) Work by OSU Student Fred Kuehn

29. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 29 Sensitivity l ∆E : the lever arm  for the instrument (Instrumental limit)  for the observed energies (Observing a source) l  t : the time resolution  the time resolution of the instrument (Instrumental limit)  the binning time to have enough statistics (Observing a source) l L: the typical distance of the sources l If the instrument doesn’t see any delay: E qg > (L·∆E)/(c·  t) l If I can see a delay ∂t : E qg = (L·∆E)/(c·  t)

30. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 30 Particle Dark Matter Some important models in particle physics could also solve the dark matter problem in astrophysics. If correct, these new particle interactions could produce an anomalous flux of gamma rays. q q or  or Z  “lines”? X X Just an example of what might be waiting for us to find!

31. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 31 Search For Dark Matter l Sources are easy to subtract l There is a diffuse background not attributed to particular point sources l To see photons from dark matter it is critical to properly model this diffuse component l OSU has started to contribute to modeling of diffuse via GALPROP  Large number of parameters  1 run takes ~6h on 2GHz machine l The lines are:  DC data (yellow)  GP_gamma generated from galprop (blue)  catalogue sources (pink)  extragalatic background in (dark pink). Work By OSU Student Aaron Sander

32. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 32 Improving On-ground Analysis Tools Standard tool is classification Tree Attempt at matching signal/background of standard… eventually improve upon Work by OSU Undergraduate Lindsey Perry

33. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 33 Remaining Major Milestones LAT final assembly complete! Delivery of LAT to NRL for environmental testing (shake/temp tests): May 2006 GLAST integration with spacecraft and testing: Fall 2006 through Summer 2007 Launch: Oct/Nov 2007, Kennedy Space Center Begin science: 1-2 months after launch Lifetime of mission: at least 5 years (goal: 10 yrs) Launch of Spitzer Space Telescope on a Delta II - Heavy

34. Richard E. Hughes, Ohio State University GLAST DOE Review Sep-28-06 Page 34 Summary l OSU has made major contributions to GLAST over the past year l OSU is the lead group for the development of algorithms for:  Calibrations  Onboard Science  As well as subsequent Testing of these algorithms on the testbed l We have begun to transition to preparing to do the science  High profile topics: GRBs, New Physics, Search for Dark Matter