DOCUMENT CHANGE NOTICE (DCN) SHEET 1 OF 1

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1 LAT Project Office SLAC DCN No. LAT-XR DOCUMENT CHANGE NOTICE (DCN) SHEET 1 OF 1 ORIGINATOR: Warren Davis PHONE: DATE: 12/10/01 CHANGE TITLE: LAT Performance Spec update ORG.: Systems Engineering DOCUMENT NUMBER TITLE NEW REV. LAT-SS GLAST LAT Performance Specification - Level II(b) Specification 2 CHANGE DESCRIPTION (FROM/TO): There are no changes to actual required performance of the LAT instrument. These proposed changes will align the wording of the LAT Performance Specification with higher-level requirements documents and will provide clarification to existing requirements. There are three types of changes in this release: 1) Changes to science requirements in section 5.2. These changes are required due to inconsistencies between the LAT Performance Spec and the GLAST Science Requirements Document, 433-SRD Additionally, the TBRs are removed. These changes are detailed in Attachment 1, Proposed Changes to LAT Performance Specification, Science Requirements. 2) Changes to the instrument requirements in section 5.3. These changes are required either for clarification or to reflect changes to higher-level mission requirements. These changes are detailed in Attachment 2, Proposed Changes to LAT Performance Specification, Science Instrument Requirements. 3) Document boilerplate updates. These changes are updates to old information in the document boilerplate, sections 1 through 4. These changes are described here: a) Change document number from LAT-SP to LAT-SS b) Update document numbers in Fig. 2-1, LAT Specification Tree c) Update document numbers in Section 4, Applicable Documents. REASON FOR CHANGE: Bring into conformance with GLAST Science Requirements Document and SC/SI IRD. ACTION TAKEN: Change(s) included in new release DCN attached to document(s), changes to be included in next revision Other (specify): DISPOSITION OF HARDWARE (IDENTIFY SERIAL NUMBERS): No hardware affected (record change only) List S/Ns which comply already: List S/Ns to be reworked or scrapped: Lis t S/Ns to be built with this change: List S/Ns to be retested per this change: DCN DISTRIBUTION: IDT List SAFETY, COST, SCHEDULE, REQUIREMENTS IMPACT? YES NO If yes, CCB approval is required. Enter change request number: APPROVALS DATE OTHER APPROVALS (specify): DATE ORIGINATOR: (Davis) Signature on file 12/11/01 Instr. Tech. Mng'r (Kamae) Signature on file 12/14/01 ORG. MANAGER: (Thurston) Signature on file 12/12/01 Instr. Scientist (Ritz) Sys. Eng. Manager (Thurston) Signature on file 12/14/01 Project Manager (Althouse) Signature on file 12/12/01 Principal Investigator (Michelson) Signature on file 12/14/01 DCC RELEASE: Doc. Control Level: Subsystem LAT IPO GLAST Project FORM # LAT-FS

2 Page 1 of 22 GLAST LAT SYSTEM SPECIFICATION Document # Date Effective LAT-SS /10/01 Prepared by(s) Supersedes Tim Thurston Warren Davis Subsystem/Office System Engineering Document Title LAT Performance Specification - Level II(b) Specification LAT-SS Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Performance Specification

3 LAT-SS LAT Performance Specification - Level II(b) Specification Page 2 of 22 CHANGE HISTORY LOG Revision Effective Date Description of Changes DCN # 1 8/31/00 Initial Release LAT-CN /10/01 Align wording of science requirements to SRD and other changes described in DCN LAT-XR

4 LAT-SS LAT Performance Specification - Level II(b) Specification Page 3 of 22 CONTENTS 1 PURPOSE SCOPE DEFINITIONS Acronyms Definitions APPLICABLE DOCUMENTS LAT SYSTEM REQUIREMENTS System Description LAT System Performance Energy Range Energy Resolution Peak Effective Area Effective Area Knowledge Single Photon Angular Resolution (SPAR) - On-axis at 68% Containment Single Photon Angular Resolution (SPAR) - On-axis at 95% Containment Single Photon Angular Resolution (SPAR) - Off axis at Field of View (FOV) Source Location Determination Point Source Sensitivity Time Accuracy Background Rejection Dead Time GRB Location Accuracy On-Board GRB Notification Time to Spacecraft AGN Location Accuracy On-Board AGN Notification Time to Spacecraft Science Instrument Requirements Description Instrument Life Science Data Interface... 14

5 LAT-SS LAT Performance Specification - Level II(b) Specification Page 4 of Data Services Operating Modes Mass CG Constraints Envelope Deleted Power Thermal Design Environmental Verification Strategy... 19

6 LAT-SS LAT Performance Specification - Level II(b) Specification Page 5 of 22 1 PURPOSE This document defines level II(b) system requirements for the GLAST Large Area Telescope (LAT). 2 SCOPE This specification captures the GLAST LAT system requirements for the space borne instrument provided by the LAT project. This encompasses the system level requirements and the functional requirements for the LAT instrument. The verification methods of each requirement are identified. The GLAST LAT Instrument Operations Center (IOC) is covered by a separate specification, LAT-SP This specification is identified in the specification tree of Figure 2-1.

7 LAT-SS LAT Performance Specification - Level II(b) Specification Page 6 of 22 Level I Project Specifications Program Plan Requirements 433-PLAN-0008 Level II System Specifications Level II(a) System Level II(b) Element Spacecraft Perf. Spec. 433-SPEC-0003 LAT Instrument Perf. Spec. LAT-SS Ops Concept Document 433-OPS-0001 GBM Instrument Perf. Spec. LAT-SC IRD 433-IRD-0001 MOC Functional Reqs Document 433-RQMT-0001 LAT Mission Assurance Reqs 433-MAR-0001 GBM IOC Specification Science Reqs Document 433-SRD-0001 GBM-SC IRD 433-IRD-0002 Mission System Specification 433-SPEC-0001 SSC Functional Reqs Document 433-RQMT-0002 EMI Reqs Document 433-RQMT-0005 LAT IOC Perf. Spec. LAT-SS Launch Veh. IRD 433-IRD-0003 Other Specifications Level III Subsystem Specifications LAT - ACD Spec. LAT-SS LAT - T&DF Spec. LAT-SS LAT TKR ICD Mech: LAT-SS Elec: LAT-SS LAT - TKR Spec. LAT-SS LAT Mech. Spec. LAT-SS LAT CAL ICD Mech: LAT-SS Elec: LAT-SS LAT - CAL Spec. LAT-SS LAT Power Subsystem Spec. LAT-SS LAT ACD ICD Mech: LAT-SS Elec: LAT-SS LAT SAS Spec. LAT-SS LAT Operations Facility Spec. LAT-SS GLAST Project Specification LAT Instrument/IOC Specification Figure 2-1 LAT Specification Tree

8 LAT-SS LAT Performance Specification - Level II(b) Specification Page 7 of 22 3 DEFINITIONS 3.1 Acronyms AGN Active Galactic Nuclei FOV Field of View FWHM Full Width Half Maximum GLAST Gamma-ray Large Area Space Telescope GRB Gamma-Ray Burst IOC Instrument Operations Center IRD Interface Requirements Document LAT Large Area Telescope LET Linear Energy Transfer MC Monte Carlo MECO Main Engine Cutoff MSS Mission System Specification PI Principal Investigator SAS Science Analysis Software SDP Science Data Processing center SI/SC IRD Science Instrument Spacecraft Interface Requirements Document SPAR Single Photon Angular Resolution SRD Science Requirements Document SSC Science Support Center TBR To Be Resolved 3.2 Definitions µsec, µs Microsecond, 10-6 second A eff Effective Area Analysis A quantitative evaluation of a complete system and /or subsystems by review/analysis of collected data. Analysis Platform toolkit for doing analysis. Arcmin An arcmin is a measure of arc length. One arcmin is 1/60 degree. Arcsec An arcsec is a measure of lengths of arc. One arcsec is 1/60 arcmin

9 LAT-SS LAT Performance Specification - Level II(b) Specification Page 8 of 22 Back Response Response as measured in the thick layers of the Tracker Background Rejection The ability of the instrument to distinguish gamma rays from charged particles. Beam Test Test conducted with high-energy particle beams cm centimeter Cosmic Ray Ionized atomic particles originating from space and ranging from a single proton up to an iron nucleus and beyond. Dead Time Time during which the instrument does not sense and/or record gamma ray events during normal operations. Demonstration To prove or show, usually without measurement of instrumentation, that the project/product complies with requirements by observation of results. E - energy ev Electron Volt Field of View Integral of effective area over solid angle divided by peak effective area. Front Response Response as measured in the thin layers of the Tracker g unit of gravitational acceleration, g = 9.81 m/s 2 Geometric Factor is Field of View times Effective Area GeV Giga Electron Volts ev Inspection To examine visually or use simple physical measurement techniques to verify conformance to specified requirements. MeV Million Electron Volts, 10 6 ev ph photons Point Source Sensitivity The flux of the weakest detectable gamma ray source. Assuming E -2 differential photon number spectrum. Primary structures The instrument primary structures include the support grid, ACD, radiators and thermal/micrometeorite shield. s, sec seconds Secondary Structures The instrument secondary structures include subsystem structures and components. Simulation To examine through model analysis or modeling techniques to verify conformance to specified requirements sr steradian, A steradian is the solid (3D) angle formed when an area on the surface of a sphere is equal to the square of the radius of the sphere. There are 4 Pi steradians in a sphere. Testing A measurement to prove or show, usually with precision measurements or instrumentation, that the project/product complies with requirements.

10 LAT-SS LAT Performance Specification - Level II(b) Specification Page 9 of 22 Validation Process used to assure the requirement set is complete and consistent, and that each requirement is achievable. Verification Process used to ensure that the selected solutions meet specified requirements and properly integrate with interfacing products. 4 APPLICABLE DOCUMENTS Documents that are relevant to the development of the GLAST LAT requirements include the following: 433-SRD-0001, GLAST Science Requirements Document, Septemper 23, IRD-0001, GLAST Science Instrument Spacecraft Interface Requirements Document, January 29, SPEC-0001, GLAST Mission System Specification, April 24, OPS-0001, GLAST Operations Concept, Draft 433-MAR-0001, Mission Assurance Requirements (MAR) for Gamma-Ray Large Area Telescope (GLAST) Large Area Telescope (LAT), October 26, 2001 GEVS-SE Rev A, General Environmental Verification Specification for STS & ELV Payloads, Subsystems, and Components, Delta II Payload Planners Guide, NPD B, NASA Policy Directive, Use of Metric System of Measurement in NASA Programs Recommended Priorities for NASA s Gamma Ray Astronomy Program , Report of the Gamma Ray Astronomy Program Working Group, April The Evolving Universe: Structure and Evolution of the Universe Roadmap , roadmap document for the SEU theme, NASA Office of Space Science, June The Space Science Enterprise Strategic Plan: Origins, Evolution, and Destiny of the Cosmos and Life, NASA Office of Space Science, November Gamma Ray Large Area Space Telescope Instrument Technology Development Program, NRA , NASA Office of Space Science, January 16, GLAST Large Area Telescope Flight Investigation: An Astro-Particle Physics Partnership Exploring the High-Energy Universe, proposal to NASA, P. Michelson, PI, November, SAE AS1773, Fiber Optics Mechanization of a Digital Time Division Command/Response Multiplex Data Bus, Society of Automotive Engineers, September, 1995

11 LAT-SS LAT Performance Specification - Level II(b) Specification Page 10 of 22 5 LAT SYSTEM REQUIREMENTS 5.1 System Description The LAT science instrument (SI) consists of an Anticoincidence Device (ACD), a siliconstrip detector tracker (TKR), a hodoscopic CsI calorimeter (CAL), and a Trigger and Dataflow system (T&DF). The principal purpose of the SI is to measure the incidence direction, energy and time of cosmic gamma rays. The measurements are streamed to the spacecraft for data storage and subsequent transmittal to ground-based analysis centers. The ACD detects energetic cosmic ray electrons and nuclei for the purpose of removing these backgrounds. It is the principle source for detection of other than gamma-ray particles. This detector element covers the TKR. Signals produced by the ACD are used by the T&DF system to identify cosmic ray electrons and nuclei entering the instrument. The TKR converts gamma rays to charged particles and measures with great precision the path of the charged particles within the TKR. Fast signals from tracks are examined in the T&DF system for likely gamma ray candidates. Once identified and at the request of the trigger system, data is read out via dataflow system. The dataflow system uses the data to assemble particle tracks and, coupled with the ACD and CAL, identify gamma rays. The CAL provides the energy measurement of incident photons and background particles. These measurements, along with the information in the TKR, are used to reconstruct the energy of the incident photons. These CAL measurements are also critical to the background particle identification and rejection. The CAL responds to T&DF requests by digitizing the energy loss in the CAL and outputs the data to the dataflow system. The CAL also provides fast signals to the T&DF system that report significant energy depositions in CAL. The T&DF system analyzes these fast signals to form requests for data readout of GLAST. The T&DF system provides the gamma-ray identification, readout of the detector measurements, assembly of gamma-ray source location and energy measurements, and the streaming of the data to the spacecraft. The spacecraft temporarily stores and then transfers the data to the IOC. The T&DF system also provides the functions for the instrument control and housekeeping operations. Structural, mechanical, electrical and shielding components are also part of the instrument. The structural components interconnect the detector components and spacecraft to ensure the required spatial relationships. Thermal/mechanical systems provide protection and stability of sensitive detector components. Electrical/electronic components provide power conditioning and data processing. A micrometeorite shield covers the instrument for protection from micrometeorites and other space debris. 5.2 LAT System Performance The performance requirements are stated for the functional life of the instrument. The goals are desired performance to be achieved without sacrificing required performance or cost and schedule objectives.

12 LAT-SS LAT Performance Specification - Level II(b) Specification Page 11 of Energy Range {SRD Table 2} The LAT shall measure gamma rays in the range of 20 MeV to greater than 300 GeV. The instrument shall have an Effective Area of greater than 300 cm 2 at 20 MeV, greater than 3000 cm 2 at 100MeV, and greater than 6400 cm 2 at 300 GeV. The design goal is to achieve an effective area greater than 1000 cm 2 at 20 MeV, greater than 8000 cm 2 at 100 MeV, and greater than 9500 cm 2 at 1 TeV Energy Resolution {Derived. Refer to SRD Table 2} The energy resolution of normal incidence gamma rays shall be better than or equal to 50% in the energy range of 20 MeV to 100 MeV, 10% in the energy range of 100 MeV to 10 GeV, and 20% in the energy range of 10 GeV to 300 GeV. Equivalent Gaussian 1 sigma. The energy resolution goal for normal incidence gamma rays is better than 8% in the energy range of 100 MeV to 10 GeV and better than 15% in the energy range of 10 GeV to 300 GeV. The energy resolution for tracked gamma rays of greater than 60 degree incidence shall be better than 6% in the energy range GeV, with an effective area >10% that of normal incidence. The energy resolution goal for tracked gamma rays of greater than 60 degree off-axis angle is better than 3% in the energy range GeV, with an effective area >20% that of normal incidence Peak Effective Area {SRD Table 2} The Peak Effective Area of the LAT shall be greater than 8000 cm 2. Determination of peak effective area shall include inefficiencies resulting from selection necessary to achieve required background rejection. The Goal is to achieve a peak effective area of greater than cm Effective Area Knowledge {Derived. Refer to SRD Table 2} The Effective Area shall be known to within 50% (1s) in the energy range of 20 MeV to 50 MeV and to within 25% (1s) in the energy range of 50 MeV to 300 GeV. The goal is to know Effective Area with 20% (1s) in the energy range of 20 MeV to 50 MeV and to within 10% (1s) in the energy range of 50 MeV to 300 GeV Single Photon Angular Resolution (SPAR) - On-axis at 68% Containment {Derived. Refer to SRD Table 2} The on-axis SPAR (space angle) at 68% containment shall be better than 3.5 for 100 MeV photons converting in the front of the tracker, and better than 6 for 100 MeV photons converting in the back of the tracker. The on-axis SPAR (space angle) at 68% containment shall be better than 0.15 for 10 GeV to 300 GeV photons converting in the front of the tracker, and better than 0.3 for 10 GeV to 300 GeV photons converting in the back of the tracker.

13 LAT-SS LAT Performance Specification - Level II(b) Specification Page 12 of 22 The goal is to have the on-axis SPAR (space angle) at 68% containment better than 3 for 100 MeV photons converting in the front of the tracker, and better than 5 for 100 MeV photons converting in the back of the tracker. The goal is to have the on-axis SPAR (space angle) at 68% containment better than 0.07 for 10 GeV to 300 GeV photons converting in the front of the tracker, and better than 0.1 for 10 GeV to 300 GeV photons converting in the back of the tracker Single Photon Angular Resolution (SPAR) - On-axis at 95% Containment {Derived. Refer to SRD Table 2} The on-axis, SPAR (space angle) at 95% containment shall be better than 3 times the on-axis SPAR (space angle) at 68% containment. The goal is to have the on-axis, SPAR (space angle) at 95% containment better than 2 times the on-axis SPAR (space angle) at 68% containment Single Photon Angular Resolution (SPAR) - Off axis at 55 {SRD Table 2} The off-axis at 55, SPAR (space angle) shall be better than 1.7 times the on-axis SPAR (space angle) at 68% containment. The goal is to have the off-axis at 55, SPAR (space angle) better than 1.5 times the on-axis SPAR (space angle) at 68% containment Field of View (FOV) {SRD Table 2} The field of view shall be greater than 2 steradians. The goal is to have the field of view greater than 3 steradians Source Location Determination {SRD Table 2} The source location determination shall be better 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 above a flat background and no cutoff up to 10 GeV. Does not include spacecraft systematics. 1 sigma radius. 1-year survey. The goal is to achieve source location determination of better than or equal to 0.3 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 above a flat background and no cutoff up to 10 GeV. Does not include spacecraft systematics. 1 sigma radius. 1-year survey Point Source Sensitivity {SRD Table 2} The point source sensitivity at greater than 100 MeV shall be better than 6 x 10-9 cm -2 s -1. Sensitivity at high galactic latitudes after a 1-year survey for a 5s detection. The goal for point source sensitivity at greater than 100 MeV is better than 3 x 10-9 cm-2 s- 1. Sensitivity at high galactic latitudes after a 1-year survey for a 5s detection.

14 LAT-SS LAT Performance Specification - Level II(b) Specification Page 13 of Time Accuracy {SRD Table 2} The time accuracy of event time measurements shall be better than 10 µsec relative to spacecraft time. The goal is to achieve time accuracy of better than 2 µsec relative to spacecraft time Background Rejection {SRD Table 2} LAT shall have a background rejection capability such that the contamination of the observed high latitude diffuse flux (assumed to be 1.5 x 10-5 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. The goal is to achieve a background rejection capability to limit the contamination of the observed high latitude flux in any decade of energy to less than 1%, assuming a flux of 1.5 x 10-5 cm-2 s-1 sr-1 (>100MeV) and a photon index of -2.1 with no spectral cut-off Dead Time {SRD Table 2} The dead time shall be less than 100 µsec per event. The goal is to achieve dead time of less than 10 µsec per event GRB Location Accuracy On-Board {SRD Table 2} The GRB location accuracy on-board shall be better than 10 arcmin, 68% confidence radius, for transients occurring within the LAT FOV, bursts with >100 reconstructed photons above 1 GeV in less than 20 seconds. The goal is to achieve GRB location accuracy on-board of better than 1 arcmin, 68% confidence radius, for transients occurring within the LAT FOV, bursts with >100 reconstructed photons above 1 GeV in less than 20 seconds GRB Notification Time to Spacecraft {SRD Table 2} The GRB notification time to spacecraft shall be less than 5 seconds after the detection of a GRB, for bursts with the characteristics given in The goal is to achieve GRB notification time of less than 2 seconds after the detection of a GRB, for bursts with characteristics given in AGN Location Accuracy On-Board While there is no specific requirement, the goal is to achieve AGN location accuracy onboard of better than 2 degrees for transients occurring within the LAT FOV, flares at high galactic latitude with change in flux greater than 2x10-6 ph cm -2 s -1 (E greater than 100 MeV) for more than 1000 seconds (68% confidence radius) AGN Notification Time to Spacecraft While there is no specific requirement, the goal is to achieve AGN notification time of less than 1 minute after recognition for transients occurring within the LAT FOV, and flares at high galactic latitude with change in flux greater than 2x10-6 ph cm -2 s -1 (E greater than 100 MeV) for more than 1000 seconds.

15 LAT-SS LAT Performance Specification - Level II(b) Specification Page 14 of Science Instrument Requirements Description The SI requirements described in this section relate more specifically to the physical, operational, and communication requirements. These requirements encompass geometries, modes of operation, operating limitations, mass and environmental conditions of the completed SI Axes Definition {SI/SC IRD } The SI shall use a definition of right-handed orthogonal axes based on the orientation of the instrument when it is mounted on the spacecraft. The X and Y-axes lie in a plane parallel to the interface plane, with the Y-axis aligned with the axis of spacecraft solar array rotation. The Z-axis is normal to the interface plane, with the +Z direction defined as pointing from the interface plane away from the spacecraft through the instrument Instrument Life {MSS 3.1.1} The performance life of the SI shall be a minimum of five years from the date the SI is placed in operation Science Data Interface {SI/SC IRD } The SI shall output science data to the spacecraft via a MIL-STD-1553 data bus interface as specified in the SI/SC IRD Data Services {SI/SC IRD 3.2.5} The SI shall communicate with the spacecraft via a serial command, telemetry, and data (CTDB) bus as defined by MIL-STD-1553B as specified in the SI/SC IRD. The communications shall include SI housekeeping data, PPS time mark signal, time distribution, analog monitoring signals, discrete control signals, configuration commands, memory and table loads, real-time pointing commands, instrument mode settings, and transient event reporting/repointing Operating Modes The SI shall accommodate the observatory modes of operation identified in the GLAST Mission System Specification (MSS), Section , Modes of Operation. These modes are Sky Survey Mode, Pointed Observation Mode and Safe Mode. Additionally, the instrument must accommodate the spacecraft load shedding function identified in the SI/SC IRD, Section 3.2.7, Fault Protection Mass {SI/SC IRD } The mass of the SI shall be less than 3000 kilograms. The SI mass includes the instrument, protective shielding and thermal control system. The SI mass does not include the interface structure and mounting hardware, star tracker and mounts, radiator supports to the spacecraft and interface cabling between the spacecraft and SI.

16 LAT-SS LAT Performance Specification - Level II(b) Specification Page 15 of CG Constraints {SI/SC IRD } The Z-axis location of the CG of the instrument shall not exceed m from the LAT/SC interface plane Envelope {SI/SC IRD } The maximum lateral, X-Y, dimensions of the SI shall be constrained to 1.8 m. The maximum Z dimension of the SI shall be constrained to 3.15 m deleted Power Average Power {SI/SC IRD: } The average power dissipation of the SI shall not exceed 650 watts per orbit Peak Power {SI/SC IRD } The peak power of the SI shall not exceed 1000 watts Peak Power Duration {SI/SC IRD } The maximum duration for the peak power dissipation of the SI shall not exceed 10 minutes for each orbit Thermal Design {SI/SC IRD: } Heat Dissipation The SI shall be capable of dissipating all thermal loads generated from electrical power usage, in addition to on-orbit thermal fluxes Heat Load from Spacecraft The SI shall be capable of dissipating up to 5 W conducted heat from the spacecraft. This does not include heat exchange between the LAT radiators and the spacecraft Environmental The environmental conditions described here encompass the normal (or standard) ground and launch conditions that the instrument may be subjected to during spacecraft integration and launch. Ground environment covers the conditions the SI could possibly endure once it is delivered for spacecraft integration and test. The instrument will be expected to sustain the on-orbit conditions for the duration of its operational life.

17 LAT-SS LAT Performance Specification - Level II(b) Specification Page 16 of deleted deleted Ground - Temperature and Humidity The instrument will be housed in environmentally controlled and monitored facilities during all phases of ground processing. The following sections give the temperature and humidity environments to which the instrument may be exposed during ground operations Non-Operating Ground Temperature Range The SI shall be capable of tolerating temperatures of 0 to 40 C while off. This is the expected temperature range of the controlled environment during ground storage and transportation Non-Operating Ground Relative Humidity The SI shall be capable of tolerating relative humidity in the range 20% to 55% while off. This is the expected range of relative humidity of the controlled environment during ground storage and transportation Assembly & Integration Temperature Range The SI shall be capable of tolerating temperatures of 15 to 25 C in air, in any operational mode. This is the expected temperature range of the controlled environment in the integration and test facilities. {Delta II Payload Planner s Guide} Assembly & Integration Relative Humidity The SI shall be capable of tolerating relative humidity in the range 35% to 55%, in any operational mode. This is the expected range of relative humidity of the controlled environment in the integration and test facilities Launch Vehicle Temperature The SI shall be capable of tolerating range of temperatures of 13 to 27 C in any operational mode, while mated to the launch vehicle prior to launch. {Delta II Payload Planner s Guide} Launch Vehicle Relative Humidity The SI shall be capable of tolerating relative humidity of the environment in the range 40% to 55%, in any operational mode, while mated to the launch vehicle prior to launch. {Delta II Payload Planner s Guide} Ground Processing Temperature Rate of Change During ground processing, the SI shall be able to withstand 5 C/hour (TBR) maximum rate of change of the temperature of the surrounding air, in any operational mode. (Note: This is an instrument safety constraint driven by the CsI crystals. It really puts a constraint on the integration and test facilities to control the rate of temperature change in the controlled environment.) {Instrument safety constraint}

18 LAT-SS LAT Performance Specification - Level II(b) Specification Page 17 of Launch - Static Load {SI/SC IRD } The instrument shall be capable of normal operation after being subjected to launch static loads given in the SI/SC IRD, 433-IRD-0001, while off deleted deleted deleted deleted Launch - Random Vibrations The instrument shall be capable of normal operation after being subjected to the acceleration spectral density (ASD) levels shown in GEVS Table D-6 while off deleted deleted Launch - Acoustic Loads {GEVS Table D-3} The instrument shall be capable of normal operation after being subjected to the acoustic loads shown in GEVS Table D-3 while off Launch - Shock {GEVS Tables D-8 and D-9} The instrument shall be capable of normal operation after the application of the external shock levels given in GEVS Tables D-8 or D-9, as applicable, attenuated to SI/SC interface values Launch Temperature {Delta II Payload Planner's Guide} The instrument shall be able to withstand a temperature range during launch of 0 to 30 C Launch - Pressure The instrument shall withstand the time rate of change of pressure in the launch vehicle fairing shown in the Delta II Payload Planner's Guide, Section 4.2.1, Figure On-orbit - Thermal Environment {SI/SC IRD 3.2.3} Earth IR and Albedo Flux Environment The SI shall be capable of normal operation in any operation mode, while any exposed surfaces are subjected to the Earth IR loads of 265 W/m^2 (hot case), and 208 W/m^2 (cold case), plus Earth Albedo factor of 0.40 (hot case), and 0.25 (cold case). This must be met, with the Radiator interface temperatures within the operational ranges described in the LAT ICD.

19 LAT-SS LAT Performance Specification - Level II(b) Specification Page 18 of Solar Thermal Flux Environment In addition to the thermal loading of , the SI shall be capable of normal operation when exposed surfaces on the +X side are subjected to sustained exposure to the solar thermal flux environment of 1419 W/m^2 (hot case), and 1286 W/m^2 (cold case). This must be met, with the Radiator interface temperatures within the operational ranges described in the LAT ICD Solar Panel Backloading In addition to the thermal loading of and.2, the SI shall be capable of normal operation when exposed surfaces and components on the +Y and Y sides of the LAT are subjected to a backloading from the solar panels of TBD watts/m^2 per side, with only one side exposed at a time, during any operating state. This must be met, with the Radiator interface temperatures within the operational ranges described in the LAT ICD Radiator Sun Exposure In addition to the thermal loading of ,.2, and.3, the SI shall be capable of normal operation when a Radiator panel is exposed to a view angle of the sun of not more than 5 degrees (TBR) for sustained periods of time, with only one Radiator exposed at a time. This must be met, with the Radiator interface temperatures within the operational ranges described in the LAT ICD Survival Solar Thermal Flux Environment While powered off, the SI shall be capable of enduring sustained full exposure to the solar thermal flux environment of 1419 W/m^2 (hot case), and 1286 W/m^2 (cold case), on any surface, while maintaining the Radiator interface temperatures within the survival ranges described in the LAT ICD deleted On-Orbit - Meteoroid and Debris Flux {MSS } The instrument shall be capable of normal operation when subjected to the expected on-orbit meteoroid and debris environment for impact probabilities of (TBR) and above, as given in the GLAST MSS Section , Meteoroid and Debris Flux.

20 LAT-SS LAT Performance Specification - Level II(b) Specification Page 19 of 22 6 Verification Strategy The verification strategy will use test, demonstration, analysis (which may include modeling or simulation), inspection, or a combination of methods to ensure that the instrument meets each specified requirement. The matrix below summarizes the requirements from Section 5 and indicates the methods of verification employed to verify compliance with each requirement. TABLE I. Summary of Science Instrument Performance Verification. Note: The verification methods are T = Test, A = Analysis, D = Demonstrate, and I = Inspect Req t # Req t Title Parameter Verification Method Energy Range/ Effective Area >300 cm 20 MeV >3000 cm 100 MeV Energy Resolution >6400 cm 300 GeV 50% (20 MeV 100 MeV, normal incidence) 10% (100 MeV 10 GeV, normal incidence) 20% (10 GeV 300 GeV, normal incidence) 6% (Energy > 10 GeV, Incidence > 60 ) Peak Effective Area >8000 cm 2 Effective Area Knowledge ((DA)/A, 1s) Single Photon Angular Resolution - 68% (on-axis) Single Photon Angular Resolution - 95% (on-axis) <50% (E= 20MeV - 50 MeV) <25% (E=50 MeV 300 MeV: <3.5 front <6 back E=10 GeV 300 GeV: <0.15 front <0.3 back < 3 x θ68% Single Photon Angular Resolution (off axis at 55 ) < 1.7 times on-axis Field of View >2 sr Source Location Determination Point Source Sensitivity (> 100 MeV) 1 arcmin A (for 1x10-7 ph cm -2 s -1 ) <6 x 10-9 cm -2 s -1, 1 year survey, 5s detection A

21 LAT-SS LAT Performance Specification - Level II(b) Specification Page 20 of 22 Req t # Req t Title Parameter Verification Method Time Accuracy Better than 10 µsec relative to S/C time Background Rejection <10% contamination of the observed high latitude diffuse flux in any decade of energy >100 MeV Dead Time <100 µs per event GRB Location Accuracy On-Board GRB Notification Time To Spacecraft <10 arcmin, 68% confidence radius, bursts with >100 reconstructed photons above 1 GeV in less than 20 seconds <5 seconds T A AGN Location Accuracy On-Board AGN Notification Time To Spacecraft No Requirement GOAL: <2 degrees No Requirement GOAL: <1 minute after recognition Instrument Life >5 years A Science Data Interface MIL-STD T, D A Data Services MIL-STD T, D Operating Modes Accommodate mission operating modes: Sky Survey, Pointed Observation and Safe Mode D Instrument Mass <3000 kg as allocated to each subsystem T CG Constraints Z-axis CG m from interface plane. T Envelope 1.8 m x 1.8 m x 3.15 m I Average Power 650 W per orbit Peak Power 1000 W Peak Power Duration 10 minutes per orbit A Heat Dissipation Dissipate all thermal loads from internal power usage, on-orbit thermal fluxes Heat Load from Spacecraft Dissipate up to 5 W conducted heat from spacecraft A Non-operating Ground Temperature Range Tolerate 0 to 40 ºC while off T, I

22 LAT-SS LAT Performance Specification - Level II(b) Specification Page 21 of 22 Req t # Req t Title Parameter Verification Method Non-operating Ground Rel. Humidity Tolerate 20% to 55% relative humidity while off T, I Assembly & Integration Temperature Tolerate 15 to 25 ºC in air in any operational mode T, I Assembly & Integration Relative Humidity Tolerate 35% to 55% relative humidity in any operational mode T, I Launch Vehicle Temperature Launch Vehicle Relative Humidity Tolerate 13 to 27 ºC in any operational mode Tolerate 40% to 55% relative humidity in any operational mode T, I T, I Ground Processing Temperature Rate of Change Tolerate < 5 ºC/hour temperature change of surrounding air T, I Launch Static Load Capable of normal operation after exposure to launch loads as given in SI/SC IRD Launch Random Vibrations Launch Acoustic Loads Launch Shock Launch Temperature Capable of normal operation after exposure to ASD levels given in GEVS Table D-6 Capable of normal operation after exposure to acoustic loads given in GEVS Table D-3 Capable of normal operation after exposure to external shock levels given in GEVS Table D-8 or D-9, as applicable, attenuated to SI/SC interface values. Tolerate 0 to 30 C in launch configuration A Launch Pressure Per Delta II Payload Planner s Guide, Section A Earth IR and Albedo Flux Environment Solar Thermal Flux Environment Solar Panel Backloading Tolerate Earth IR loads of 265 W/m^2 (hot case), and 208 W/m^2 (cold case), plus Earth Albedo factor of 0.40 (hot case), and 0.25 (cold case) W/m^2 (hot case), and 1286 W/m^2 (cold case), sustained exposure on +X side. TBD W/m^2 per side. A Radiator Sun Exposure < 5 degrees (TBR) sun view angle, one side at a time A

23 LAT-SS LAT Performance Specification - Level II(b) Specification Page 22 of 22 Req t # Req t Title Parameter Verification Method Survival Solar Thermal Flux Environment Survive unpowered in solar flux environment of 1419 W/m^2 (hot case), and 1286 W/m^2 (cold case), sustained exposure on any surface On-Orbit Meteoroid and Debris Flux Instrument must withstand meteoroid and debris flux estimates given in GLAST MSS Section for impact probabilities of and above A