1. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 GLAST Large Area Telescope Gamma-ray Large Area Space Telescope GLAST Large Area Telescope LAT Pre-Shipment Review Science Requirements Verification Steve Ritz, Bill Atwood

2. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 2 Science Requirements Verification  LAT energy range and FOV are vast. Verification consists of a combination of simulations, beam tests, and cosmic ray induced ground-level muon tests. –primary verification is done by analysis, using the simulation (see following slides) –ground-level muon data provide additional inputs to the simulation related to instrument characteristics (dead channels, noise, uncovered idiosyncrasies, geometry checks, etc.) –beam tests provide inputs for tuning the simulation and reconstruction algorithms, and they also sample performance space over the full energy range  For science performance, beam tests can be done with just a few towers together (2 TKR, 3 CAL, 5 ACD tiles).  Full-LAT tests are mainly functional tests.

3. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 3 How the Analysis Pieces Fit Together Instrument Response geometry particle transport, interactions (GEANT4) sensor responseelectronics and data system dead channels, impacts noise, etc. triggeronboard filter onboard science background fluxes gamma events Event Reconstruction Event Classification Performance High-level Science Analysis detailed flux review J. Ormes et al., LAT- TD-08316- 01 sky model and benchmark fluxes muon test data, SVAC runs FSW algorithms wrapped into SAS; FES+Testbed beam test; self- consistency checks, basic physics checks beam test check planning a review by the SWG in December

4. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 4 Aside: some definitions 68%95% Effective area (total geometric acceptance) (conversion probability) (all detector and reconstruction efficiencies). Real rate of detecting a signal is (flux) A eff Point Spread Function (PSF) Angular resolution of instrument, after all detector and reconstruction algorithm effects. The 2-dimensional 68% containment is the equivalent of ~1.5  (1- dimensional error) if purely Gaussian response. The non-Gaussian tail is characterized by the 95% containment, which would be 1.6 times the 68% containment for a perfect Gaussian response.

5. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 5 Example (simplified) recipe: Aeff  Throw benchmark flux of photons at 6m 2 target in which LAT is embedded –“all_gamma” flux, covering all relevant angles and energies –target area optimized for efficiency while maintaining correct distribution  Pass all events through full simulation, trigger, filter, reconstruction, background rejection, good event selections, etc. (previous slide)  In bins of energy and incident angle (instrument coordinates), calculate Aeff: (# events passing/#events thrown) * 6m 2  Field of view is given by Aeff as a function of incident angle –defined in requirements as integral of Aeff over solid angle normalized to Aeff at  =0.

6. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 6 Performance Analysis  Enormous data sets generated for backgrounds (>5 billion events, sampling orbit variations) and signals (~30 million events).  LAT provides very detailed information about each event. –the performance is as much a function of analysis choices as hardware performance. Many “knobs” to turn. Analysis choices will be different for different science topic optimization. –results shown here are for a baseline set of choices that generally represent the most challenging cases.  Great improvements in analyses for energy reconstruction, direction (PSF), and background rejection.

7. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 7 4 Stages of Post Recon Event Analysis Tag – GR_v9r10 Input: Recon Output: GlastClassier  Energy reconstruction selection –select best energy method (among 3)  PSF- Image control –select best gamma direction  Background Rejection –(a) divide events into categories. For each category, a set of selections and classification tree –(b) global cuts and additional classification tree

8. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 8 Level 1 and Level 2 Requirements  14 of 18 Level 2 (SRD) requirements covered in these slides. –two requirements, on time accuracy and deadtime, covered elsewhere by direct test. –verification of remaining two requirements on GRB localization onboard and notification time await completion of the onboard science algorithm implementation in FSW.  7 of 7 Level 1 science requirements covered in these slides.

9. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 9 LPS7 - Gamma Energy Range  Requirement: –The LAT shall measure gamma rays in the range of 20 MeV to greater than 300 GeV.  Verification: –flows directly into LPS143, LPS144, LPS145 (see following)  Compliance Statement: LAT Complies

10. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 10 LPS143 - Effective Area at 20 MeV  Requirement: The instrument shall have an Effective Area of greater than 300 cm 2 at 20 MeV.  Test/Analysis Summary: The all_gamma simulation (v9r6) is used to calculate the effective area at downlink, after onboard trigger and onboard filter selections.  Result: At normal incidence (cos(  )<-0.99) at 20 MeV, the effective area is 1600 cm 2 (1400 cm 2 with reconstructed track requirement). Additional selections, specific to particular science topics, will trade effective area against other performance parameters (background fraction, PSF, energy resolution).  Compliance Statement: LAT Complies 20 MeV 1 GeV 10 GeV 100 GeV

11. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 11 LPS144 - Effective Area at 100 MeV  Requirement: The instrument shall have an Effective Area of greater than 3000 cm 2 at 100 MeV.  Test/Analysis Summary: The all_gamma simulation is used to calculate the effective area after all selections.  Result: At normal incidence at 100 MeV, the effective area is 3,700 cm 2, for the current standard background rejection selections. Different selections, specific to particular science topics, will trade effective area against other performance parameters (background fraction, PSF, energy resolution).  Compliance Statement: LAT Complies

12. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 12 LPS145 - Effective Area at 300 GeV  Requirement: The instrument shall have an Effective Area of greater than 6400 cm 2 at 300 GeV.  Test/Analysis Summary: The all_gamma simulation is used to calculate the effective area after all selections.  Result: At normal incidence at 300 GeV, the effective area is 7,000 cm 2, for the current standard background rejection selections. Different selections, specific to particular science topics, will trade effective area against other performance parameters (background fraction, PSF, energy resolution).  Compliance Statement: LAT Complies –further work underway on optimization at the highest energies log(E) (smoothed)

13. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 13 LPS15 - Peak Effective Area  Requirement: The peak effective area of the LAT shall be greater than 8000 cm 2.  Test/Analysis Summary: The all_gamma simulation is used to calculate the effective area after all selections.  Result: At normal incidence, the peak effective area is 9,000 cm 2, for the current standard background rejection selections. Different selections, specific to particular science topics, will trade effective area against other performance parameters (background fraction, PSF, energy resolution).  Compliance Statement: LAT Complies (smoothed) log(E)

14. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 14 LPS32 - Field of View  Requirement: The field of view shall be greater than 2 sr.  Test/Analysis Summary: The all_gamma simulation is used to calculate the effective area after all selections.  Result: In the energy range corresponding to that of the peak effective area, the FOV is 2.2 sr. Different selections, specific to particular science topics, will trade effective area and FOV against other performance parameters (background fraction, PSF, energy resolution).  Compliance Statement: –LAT Complies log(E)

15. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 15 LPS18, LPS150 - Effective Area Knowledge  Requirement: The effective area shall be known to within 50% (1-sigma) in the energy range 20 MeV to 100 MeV (LPS18). The effective area shall be known to within 25% (1-sigma) in the energy range 100 MeV - 300 GeV (LPS150).  Test/Analysis Summary: –Sources of uncertainty, estimates geometry, active area of silicon detectors <2% material, probability of conversion <1% ACD material conversions <1% reconstruction inefficiencies <2% energy calibration impacts 1 GeV) –Checks for consistency, and monitoring, will be done on orbit.  Result: 1 GeV)  Compliance Statement: LAT Complies  [Note this is a requirement that is internal to LAT. It is not a mission-level science requirement.]

16. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 16 LPS10 - Energy Resolution 20-100 MeV  Requirement: The energy resolution of normal incidence gamma rays shall be better than or equal to 50% in the energy range of 20-100 MeV, equivalent Gaussian 1sigma.  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: see following slide  Compliance Statement: LAT Complies.

17. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 17 LPS146 - Energy Resolution 100 MeV - 10 GeV  Requirement: The energy resolution of normal incidence gamma rays shall be better than or equal to 10% in the energy range of 100 MeV - 10 GeV, equivalent Gaussian 1sigma.  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: See following slide  Compliance Statement: LAT Complies.

18. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 18 Off Axis: cos(  ) > -.7 On Axis: cos(  ) < -.95 Default "Best" Default "Best" Energy Resolution log(E)

19. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 19 LPS147 - Energy Resolution 10 GeV - 300 GeV  Requirement: The energy resolution of normal incidence gamma rays shall be better than or equal to 20% in the energy range of 10 GeV - 300 GeV, equivalent Gaussian 1sigma.  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: See previous slide  Compliance Statement: LAT Complies.

20. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 20 LPS12 - Off-axis Energy Resolution  Requirement: The energy resolution of tracked gamma rays of greater than 60 degrees incidence shall be better than 6% in the energy range 10 to 300 GeV, with an effective area > 10% that of normal incidence.  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: see previous slide  Compliance Statement: LAT Complies.

21. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 21 CAL3-6, 21, 22, 26, 29  These requirements are flowed down from higher-level requirements to level 3 CAL requirements, and they are verified automatically by the verification of the preceding requirements: –CAL3-6 CAL shall support LAT Calorimetry in the energy range 20 MeV to 300 GeV, verified along with LAT-LPS7. –CAL3-21 (Energy resolution 20-100 MeV) verified along with LAT- LPS10. A separate analysis will also be done using photons that don’t convert in the TKR. –CAL3-22 (energy resolution 100 MeV - 10 GeV) verified along with LAT-LPS146. –CAL3-26 (energy resolution 10 GeV - 300 GeV) verified along with LAT-LPS147. –CAL3-29 (off-axis energy resolution >10 GeV) verified along with LAT-LPS12.

22. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 22 CAL3-56  Requirement: Each layer of the calorimeter shall position the centroid of a Minimum Ionizing charged particle energy deposition to less than 3.0 cm (1-sigma) in all three dimensions for particle incident angles of <45 degrees.  Test/analysis Summary: use ground muon data collected during LAT testing.  Result: all layers <<3.0 cm –(typically <1cm)  Compliance Statement: LAT Complies (SVAC B30 runs 135005404 to 14)

23. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 23 CAL3-59  Requirement: The single particle angular resolution at 68% containment for the CAL shall be better than 15 degrees * cos 2 (  )for cosmic muons traversing all 8 layers.  Test/analysis Summary: use ground muon data collected during LAT testing (SVAC B30 runs 135005404 to 14).  Result: (see following slide)  Compliance Statement: LAT Complies

24. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 24 CAL3-59

25. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 25 CAL3-37  Requirement: The calorimeter shall be capable of energy calibration in orbit using energy depositions from the array of cosmic ray particles.  Compliance Statement: LAT Complies Species (Z)Abundance Relative to H Enormal (MeV) * He (2)14%45 C (6)0.38%400 N (7)0. 096%550 O (8)0.35%720 Ne (10)0.062%1120 Mg (12)0.073%1610 Si (14)0.054%2200 Fe (26)0.041%7600 * Does not include quenching effects Range 5-  Emin (MeV) Emax (MeV) MeV/ADC LEX821000.03 LEX1210000.27 HEX86080002.2 HEX1607000019 Fluxes and energy depositions Calorimeter scales to be calibrated Estimates of collection times for 1000 good events per log: 1-2 weeks Detailed simulation studies underway to prepare the on-orbit data analysis.

26. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 26 LPS21, LPS151 - SPAR at 100 MeV  Requirement: The single photon angular resolution (SPAR) at 68% containment for 100 MeV photons at normal incidence shall be better than 3.5 degrees for the photons converting in the front of the TKR (LPS21) and better than 6 degrees for photons converting in the back of the TKR (LPS151).  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: see following slides.  Compliance Statement: LAT Complies.

27. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 27 LPS22, LPS152 - SPAR at >10 GeV  Requirement: The single photon angular resolution (SPAR) at 68% containment for >10 GeV photons at normal incidence shall be better than 0.15 degrees for the photons converting in the front of the TKR (LPS22) and better than 0.3 degrees for photons converting in the back of the TKR (LPS151).  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: see following slides.  Compliance Statement: LAT Complies.

28. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 28 LPS26 - SPAR at 95% Containment  Requirement: The on-axis SPAR at 95% containment shall be better than 3 times the on-axis SPAR at 68% containment.  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: see following slides.  Compliance Statement: LAT Complies.

29. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 29 Thin Radiator PSF Thick Radiator PSF Off Axis: cos(  ) > -.7 On Axis: cos(  ) < -.95 log(E) = requirement, compare w/ blue line

30. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 30 LPS29 - Off-axis SPAR  Requirement: The off-axis SPAR at 55 degrees shall be better than 1.7 times the on-axis SPAR at 68% containment.  Test/Analysis Summary: The all_gamma simulation is used to calculate the energy response after all selections.  Result: see following slides.  Compliance Statement: LAT Complies.

31. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 31 PSF off axis  Thin (Front)Thick (Back) 100 MeV 1 GeV 10 GeV 100 GeV 300 GeV 100 MeV 1 GeV 10 GeV 100 GeV 300 GeV 55˚

32. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 32 LPS35 - Point Source Location Determination  Requirement: The source location determination shall be less than or equal to 0.5 arcmin for a source flux of 1 x 10 -7 ph cm -2 s -1 (E > 100 MeV) or greater. Assumes high galactic latitude source with spectral index -2 (1/E 2 ) above a flat background and no cutoff up to 10 GeV. Does not include spacecraft systematics. 1  radius. 1-year survey.  Test/Analysis Summary: The instrument response functions (IRFs) derived from the full event reconstruction analysis are used to calculate the localizations.  Result: location determination <0.4 arcmin (to be updated)  Compliance Statement: LAT Complies.

33. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 33 LPS38 - Point Source Sensitivity  Requirement : The point source sensitivity (E > 100 MeV) shall be <6x10 -9 cm -2 s -1. Sensitivity at high galactic latitudes after a 1-year survey for a 5 sigma detection.  Test/Analysis Summary: The instrument response functions (IRFs) derived from the full event reconstruction analysis are used to calculate the localizations.  Result: point source sensitivity is <4x10 -9 cm -2 s -1. See following slide.  Compliance Statement: LAT Complies.

34. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 34 C&A at Stockholm 29 Aug 06 T. Burnett Point source sensitivity: Check TS for 4x10 -9 cm -2 s -1, one year livetime  E -2 power law  Standard EGRET extragalactic background  Combined 0-66 deg in one bin, scanning mode  Ignore effects of dispersion Class CTBCORE range TS frontback #10.1-0.51.900.27 #20.5-0.74.421.40 #30.7-0.857.303.65 #40.85-16.864.14 (Sum)20.489.46 2-4 combined0.5-119.108.94 DC2 classA21.010.0 ‘5  ” requirement:  (TS) > 25 Total for LAT is 28.0

35. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 35 LPS44 - Background Rejection Capability  Requirement : LAT shall have a background rejection capability such that the contamination of the observed high latitude diffuse flux (assumed to be 1.5x10 -5 cm -2 s -1 sr -1 ) in any decade of energy ( > 100 MeV) is less than 10%, assuming a photon spectral index of -2.1 with no spectral cut-off.  Test/Analysis Summary: The background simulation and the extragalactic diffuse gamma-ray flux simulation are used to calculate the residual rates after all trigger, filter, reconstruction, and event selections.  Result: see following slide.  Compliance Statement: LAT Complies directly for E>3 GeV. For the energy band 100 MeV 10%. For this energy range, the residual contamination energy spectrum will be subtracted from the measured diffuse energy spectrum. A systematic error due to the background subtraction of <10% will bring the LAT into compliance. An analysis will be presented at the science performance review, with final verification on orbit.

36. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 36 Background Contamination log(E) Resulting spectra Background fraction by decade of energy (no subtraction) signal bkgd min req result of updated background model

37. Science Requirements Verification GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 2 of 12 37 Summary  LAT meets or beats Science Requirements –instrument data idiosyncrasies and relevant real-world behavior (e.g., bad channels) uncovered during testing incorporated into the simulation. –beam test results will be used to update the simulation. –further analysis to be performed on background rejection and effective area knowledge requirements. Updates to come on point source localization and on-orbit CAL calibration analyses. –these are analysis tasks that are decoupled from instrument shipment schedule.  Verification of two science requirements pending completion of FSW burst algorithm implementation.  Review by the GLAST Science Working Group of performance against all three requirements tables (GBM, LAT, Observatory) in the Science Requirements Document (SRD) later this year.