glast proposal revie file• many studies complete prior to nov ’99 proposal

GLAST LAT Project DOE/NASA Baseline-Preliminary Design Review, January 8, 2002

Document: LAT-PR-00403 Section 5.0 Systems Overview 1

GammaGamma--ray Large ray Large Area Space Area Space TelescopeTelescope

GLAST Large Area Telescope:GLAST Large Area Telescope:

Systems Overview WBS: 4.1.2

Tim ThurstonStanford Linear Accelerator CenterSystems Engineering Manager

[email protected]



TopicsTopics

• System Key Requirements• Technical Trades• Systems Overview• LAT Design Heritage - Highlight• System Performance • Systems Engineering & Configuration Management• Schedule/Milestones



LAT Key Science RequirementsLAT Key Science RequirementsLevel II(b) Specification No: LAT-SS-00010-01

Parameter Range Requirement PDR

Energy Resolution 20MeV-100MeV < 50%, Normal Incidence 9% @ 100 MeV

100 MeV - 10 GeV <10%, Normal Incidence 8% @ 10 GeV

10 GeV - 300 GeV <20%, Normal Incidence < 15%

Energy > 10 GeV <6% Incidence > 60º <4.5%

Effective Area 1, 10 GeV (peak within range) > 8000 cm2 10,000 cm2 @ 10

GeV

Field of View > 2 sr 2.4 sr

Single Photon Angular Resolution - 68% 100 MeV < 3.5º/6º

(front/back) 3.37º/4.64º (front/total)

10 GeV - 300 GeV < 0.15º/0.3º (front/back) .086º/.115º (front/total)

Pointing knowledge < 7 arcsecond 5 arcsecond

Dead Time < 100 µs/event 20 µsec



LAT Key Design RequirementsLAT Key Design RequirementsLevel II(b) Specification No: LAT-SS-00010-01

Parameter Requirement PDR

Orbital Period 90 minutes 90 minutes

Instrument Mass < 3000 kg 2614 kg

CG Constraints < 0.246 m 0.180 m

Envelopex: < 1.8 my: < 1.8 mz: < 3.15 m

x: 1.794 my: 1.794 mz: 1.044 m

Static Load Thrust +6.0 +/- 0.6 g (See SI/SC IRD)* comply

Lateral +/- 4.0 g (@ Liftoff) comply

Average Power (orbit average) < 650 watts 528 watts

Peak Power < 1000 watts 603 watts



LAT Technical Trade Studies LAT Technical Trade Studies • Many Studies Complete prior to Nov ’99 proposal• Studies completed since selection

– Tracker SSC size, pitch instrument footprint, mass• SSD spec finalized, prototypes made and evaluated

– Tracker radiator thickness distribution– Grid Material: Al vs. CFC

• Aluminum selected– ACD Segmentation

• 104 segments selected– Grid Pitch

• Pitch increased 1 mm– SAA protection scheme

• PMT current limit in addition to SAA alert protective action– Optimized I&T, calibration and verification test plans

• Ongoing Studies– ACD Skirt – Hardware Triggers/Onboard Filter – Optimized on-board processors– Thermal Control System



LAT System Overview (Continued)LAT System Overview (Continued)Instrument Configuration – Major Mechanical & Thermal Components

Thermal/micro-meteorite shield (MLI and ceramic blankets)

Anticoincidence Detector (ACD) surrounds TKR

Trackers (TKR) mount to top flange of Grid

Grid support structure (aluminum)

Radiators mount to Grid and Spacecraft (SC)

Calorimeters (CAL) inside Grid

Electronics mount to CAL bottom platesHeat pipes on top of

GridSpacecraft mount points (4x)Radiator

(aluminum)



LAT System Overview (Continued)LAT System Overview (Continued)

Instrument Configuration Major Electrical Components

Anticoincidence Detector• 5 sided, composed of segmented plastic

scintillator tiles• 194 photo multiplier tubesTracker• 16 Modules• 8.8 105 channels (18 layers/module) Si Strip Det.Calorimeter• 16 Modules• 8 x 12 CsI bars x 2 channelsData Flow & Electronics• 16 Tracker/CAL Electronics Modules (TEM)• 2 Spacecraft Interface Units (1 box - SIU)• 2 ACD-Electronics Modules, 2 Global Triggers

modules ( 1 box - GASU)• 5 Processor Modules• 2 Power Distribution Units (1 box –PDU)

DAQ EM DAQ EM DAQ EM DAQ EM




TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

TKR

ACD

spare

EP-3

T / C PS T / C PS T / C PS T / C PS




EP-RESEP-1 EP-2

spare spare

EP-4

CAL CAL CAL CAL

CAL CAL CAL CAL

CAL CAL CAL CAL

CAL CAL CAL CAL

SIU Pwr Dist. Box

GASU

- ACD

-TKR

- CAL

- TEM

- T/C PS

- GASU, EP, PDU, SIU



LAT Operating ModesLAT Operating Modes

Launch Mode

Early Orbit Mode

Observatory Verification

Mode

Normal Operations

Mode*

Re-entry Mode

Safe Mode

Software Mode

Hardware Mode

Survival Mode

Safe Mode Recovery

Standby/ Engineering

Mode

* Science Operations



LAT Design LAT Design -- Flight HeritageFlight Heritage

Examples of Flight Experience & Heritage Application• Balloon Flight Experiment

– Successful implementation and flight tested a prototype tower consisting EM units from ACD, Tracker, Calorimeter, and DAQ

– Demonstrated Trigger and data & command communications along with on-board data storage

• Thermal Subsystem– Heat Pipes & Thermal Control: Designed by Lockheed Martin with

flight heritage from MILSTAR, Classified, Iridium and CommercialRemote Sensing (CRSS)

• Structural– Tracker Tower: Engineering support Hytec Inc., provider of

advanced composite frames and materials for flight programs such as STEREO and FORTE

• Processor– British Aerospace RAD750 radiation hardened PowerPC, a follow-

on to the flight proven RAD6000 family



System Design Complexity ComparisonSystem Design Complexity ComparisonElectrical DesignBaBar vs. LAT BaBar LAT

Main Physics Detector Systems 5 3Tracker

Detector Technology Si Strip Si StripChannels 100,000 850,000Signal Processing 7 bit 1 bit

Radiation Hardness > Mrad <10 KradCalorimeter

Detector Technology Cesium Iodide Cesium IodideChannels 14,000 1,500Dynamic Range 18 bit/diode 15 bit/diodeDigitization Rate 4 MHz < 10 KHzFE Electronics Servicable No No

3rd Detector System (DIRC/ACD)Photo Multiplier Tube Channels 11,000 200Pulse Processing Height+(2ns)Time+Charge Height

Trigger & Data FlowTrigger Input Channels 14,000 800 CAL/TKR Layer OR's

L1 Trigger Rate 2 KHz < 10 KHzTKR Trigger Processing curve fitting simple 3-in-a-rowCAL Trigger Processing energy sum simple 3-in-a-rowDeadtime after Trigger 2 µsec 20 µsecSystem Dead-time < 0.5 % at 2 KHz 20% at 10 KHz

Event ProcessingReal Time Event Processors 240 4Event Data Size 30 kb 1-2 kb



Systems Performance Budget (1)Systems Performance Budget (1)Mass Budget (Kg)

13-Dec-01 Estimate Recm'd ReserveItem (Kg) (Kg) %ACD 228.1 33.0 14.5%

Tracker 504.9 15.1 3.0%

Calorimeter 1,466.3 98.8 6.7%

Trigger & Data Flow 184.4 42.2 22.9%

Grid/thermal 230.0 63.5 27.6%

Instrument Total 2,613.7 252.7 9.7%

Instrument Allocation 3,000.0

% Reserve 14.8%LAT Mass

24002500260027002800290030003100

06-Jan-99

06-Jan-00

05-Jan-01

05-Jan-02

05-Jan-03

05-Jan-04

04-Jan-05

04-Jan-06

Mas

s - K

G

Instrument Allocation: 3000 kg Instrument Reserve at PDR: 14.8%

Goal for PDR Reserve > 9.9% Goal for CDR Reserve > 5.4%

Goals estimated using guidelines given in ANSI/AIAA G-020-1992 "Estimating and Budgeting Weight and Power Contingencies for Space Craft Systems"

Proposal SRR I-PDR I-CDR Ship Inst . Launch

Current

Trigger

A llocat ion



Systems Performance Budget (2)Systems Performance Budget (2)

Power Budget (Watts)30-Nov-01 Estimate Recm'd Reserves

Item (Watts) (Watts) %ACD 12.3 2.2 18.1%

Tracker 168.9 15.2 9.0%

Calorimeter 77.2 12.4 16.1%

Trigger & Data Flow 244.9 44.3 18.1%

Grid/thermal 24.5 2.2 9.0%

Instrument Total 527.8 76.4 14.5%

Instrument Allocation 650.0

% Reserve 23.1%LAT Power

400450500550600650700

06-Jan-99

06-Jan-00

05-Jan-01

05-Jan-02

05-Jan-03

05-Jan-04

04-Jan-05

04-Jan-06

Pow

er -

Wat

ts

Instrument Allocation: 650 Watts Instrument Reserve at PDR: 23.1%

Goal for PDR Reserve > 15% Goal for CDR Reserve > 10%

Goals estimated using guidelines given in ANSI/AIAA G-020-1992 "Estimating and Budgeting Weight and Power Contingencies for Space Craft Systems"

Proposal SRR I-PDR I-CDR Ship Inst . Launch

Current

Trigger

A llocat ion



Systems Engineering&

Configuration Management



Systems EngineeringSystems Engineering

System Design

RequirementManagement

4.1.2.1

LAT SystemConfigurationManagement

4.1.2.6

DocumentManagement

Risk/Reliability

System Analysis4.1.2.3

Science Analysis

StructuralAnalysis

Thermal Analysis

CyberDoc

DOORs

Level II/III ChangeControl BoardPower Budget

Mass Budget

LAT Systems EngineeringTim Thurston(WBS 4.1.2)

Interface Control

Database

FMEAs

SystemVerificaiton

System Validation

IV&V Support

Verification Plan



Requirements FlowRequirements Flow

LAT - ACD Spec. LAT-SS-00016

LAT - TKR Spec. LAT-SS-00017

LAT - CAL Spec. LAT-SS-00018

LAT - T&DF Spec. LAT-SS-00019

Leve

l IPr

ojec

t Sp

ecifi

catio

nsLe

vel I

I(a) S

yste

m

Leve

l III

Subs

yste

m S

peci

ficat

ions

LAT Operations Facility Spec.

LAT-SS-00021

ProgramRequirements

Leve

l II(b

) Ele m

ent

LAT – ACD ICDMech: LAT-SS-00241Elec: LAT-SS-00363

LAT SAS Spec. LAT-SS-00020

LAT InstrumentPerf. Spec. LAT-SS-00010

MOC Functional Reqs Document

433-RQMT-0001

LAT IOCPerf. Spec.LAT-SS-00015

Leve

l II S

yste

m S

peci

ficat

ions

LAT Power Subsystem Spec.

LAT-SS-00136

LAT Mech. Spec. LAT-SS-00115

Other Element Specifications

Ops Concept Document

433-OPS-0001

LAT Mission Assurance Reqs

433-MAR-0001

Mission System Specification433-SPEC-0001

Science ReqsDocument 433-SRD-0001

Design Standards

LAT-SC IRD433-IRD-0001

LAT – CAL ICDMech: LAT-SS-00273Elec: LAT-SS-00238

LAT – TKR ICDMech: LAT-SS-00138Elec: LAT-SS-00176

GLAST Project Specification LAT Instrument Specification LAT IOC Specification



System Requirements Flow Down & TrackingSystem Requirements Flow Down & TrackingGLAST Mission & LAT Project have selected Telelogic DOORS® requirements management tool

Systems Engineering

DOORS

Level 4Test Plans

Level 4Performance

Specifications

Level 3Performance

Specifications

Level 3Test Plans

Level 2Performance

SpecificationsLevel 2

Test Plans

Level 2LAT

Requirements

Level 2Test

Requirements

VerificationMatrix

Level3LAT

Requirements

Level 4LAT

Requirements

Level 3Test

Requirements

Level 4Test

Requirements

Requirements Management:• Tracking• Flowdown• Verification



LAT Configuration ManagementLAT Configuration Management

Online Access for Status Reporting and Real-Time Inquiries

BaselineDocuments

CIDL

CISelection

ProposedChange

ChangeApproval

(Manager or CCB)

ChangeVerification

ConfigurationAudits

Online Access to LAT Team

Configuration Change ControlConfiguration Change Control

Configuration IdentificationConfiguration Identification Configuration Status Configuration Status AccountingAccounting

Configuration Configuration VerificationVerification



CCB ProcessCCB Process

Need for ChangeIdentified

Responsible Project Element(RPE) submits Document Change

Notice (DCN) for managerapproval

Impact to requirements,cost, schedule?

Class III changeChange is implemented and DCN

is distributed to LAT team

Class I or II changeRPE submits a Change Request

(CR) for CCB screening

CR is sent to the ConfigurationControl Board for approval

GLAST Project Office (GPO) approval required?

CR is sent to GPO for approvalIf approved, the change is

implemented and the CR and DCNare distributed to the LAT team

CLASS DEFINITIONSClass I - MissionClass II - IPOClass III - Subsystems

NO, Class II

YES, Class I



System Requirements & Analysis



System Requirements Tracking (Example)System Requirements Tracking (Example)LAT Level IIb Requirements

Parameter Constraint Predicted Performance

(PDR)

Requirement Goal Verification Spec Ref

630 cm2 to Sim,ground BT (>10,000 TPT, 20±5 MeV, NI )2000 cm2 Sim,(being worked) BT (> 5000 TPT, 100±10 MeV, NI)

1, 10 GeV (peak within range)

>10,000 cm2

@10 GeV> 8000 cm2 > 12,000 cm2 Sim,

BT (> 1000 TPT, 1±0.1 & 10±1 GeV, NI) 5.2.3

8,000 - 10,000 Sim,cm2 BT (> 1000 TPT, 10±1 GeV, extrapolate)

1 TeV TBD > 9500 cm2 Sim 5.2.1TBD Sim (every 10 MeV),

BT (see cases above)

TBD Sim (every 10 MeV from 50 to 90 MeV, then see cases above),BT (see cases above)

100 MeV

300 GeV

Aeff 20 MeV > 300 cm2 > 1000 cm2

> 6400 cm2 5.2.1

5.2.1

> 3000 cm2 > 8000 cm2 5.2.1

5.2.4

50 – 300 MeV < 25 % < 10 % 5.2.4

Aeff

knowledge (1σ)

20 – 50 MeV < 50 % < 20 %

Comments:

TPT – tagged photon trigger

For 300 GeV data:

BT – beam test

NI – normal incidence

Simulations must match measured backsplash rates to better than 10% – earlier measurements must be reviewed and, if necessary, another set of measurements must be made.

Effective Area vs. Energy

0

5000

10000

15000

0.01 0.1 1 10 100 1000

Energy (GeV)

Aef

f (cm̂

2) SpecGoalPDR

Single point from SRD



FMEA & Reliability RequirementsFMEA & Reliability Requirements

As described in the MAR



Probabilistic Risk Assessment CategoryProbabilistic Risk Assessment Category1 >10% (<90%)

None

None

2 <10%>1% (>90% <99%)

None

None

3 <1% (>99%)

None

4 Failure Unlikely - No Known failure, Large Margins

None

Prob

abili

ty o

f Occ

urre

nce

(Mis

sion

Suc

cess

)

5 Failure Not Credible- Specific mitigation action

None

5 No Effect

4 Loss of non critical function a. not needed, b. backup available

3 Degraded Mission (meets minimum science mission)

2 Loss of Science (does not meet minimum science mission)

1 Total Loss of Mission

Criticality - Consequence of Failure

Risk High Medium Low



Reliability AllocationReliability AllocationMission Elements Systems Subsystems

Launch Vehicle

??%(Pf = .??)

Mission70%

(Pf = .3)

GSE??%

(Pf = .??)

Space Craft85%

(Pf = .15)

Observatory85%

(Pf = .15)

GBM85%

(Pf = .15)

LAT85%

(Pf = .15)

Elec/DA96%

(Pf = .04)

Mechanical/ Thermal

99%(Pf = .01)

CAL96%

(Pf = .04)

TKR96%

(Pf = .04)

ACD96%

(Pf = .04)

Reliability is defined as the probability of successfully meeting mission objectives at end of life. Pf is probability of failure.



Operability AllocationOperability AllocationSystems Subsystems

LAT85%

Elec/DA90%

Mechanical/ Thermal

100%

CAL90%

TKR90%

ACD98.5%

Operability is defined as the fraction of the component or subsystem required to be operational in order for the instrument to meet minimum mission performance at end of life.



Risk & Risk MitigationsRisk & Risk Mitigations• Power & Mass

– Established Power & Mass Review Board to control the power growth

• Trigger/Background Filtering– Flexible compute/software architecture– Trigger/Filtering studies underway

• Thermal Control System Ground Testing– Enhanced validation program– Additional concepts being studied

• Calorimeter: Diode/Crystal optical bonding– Pre-production testing program– Optional non-bonded pin diode configuration



Level III Milestones (1)Level III Milestones (1)vDE Activity

DescriptionStartDate

FinishDate

ND AV

Instrument Project Office (Level 3ACD Subsystem Requirements Review 03/20/01A 2 6

Tracker Subsystem Requirements Review 03/22/01A 2 4

Calorimeter Subsystem Requirements Review 03/28/01A 2 5

Science Analysis Software Requirements Review 04/20/01A 2 D

Electronics & DAQ Subsystem Requirements Review 04/25/01A 2 7

Mechanical Subsystem Requirements Review 05/02/01A 2 8

IOC Requirements Review 05/03/01A 2 B

Flight Software Requirements Review 05/30/01A 2 7

Tracker PDR 06/19/01A 2 4

Anticoincidence Detector PDR 07/25/01A 2 6

Calorimeter PDR 07/27/01A 2 5

Mechanical Systems PDR 08/15/01A 2 8

Electronics & DAQ PDR 08/16/01A 2 7

Flight Software PDR 08/16/01A 2 7

IOC PDR 08/17/01A 2 B

FY01 FY02 FY03 FY04 FY05 FY06

© Primavera Systems, Inc.

Run Date 11/19/01 14:26 *** DRAFT *** Sheet 1 GLAST-LAT ProjectProject Milestones

Level 3



Level III Milestones (2)Level III Milestones (2)Activity


FinishDate

ND AV

Instrument Project Office (Level 3)Science Analysis Software PDR 08/17/01A 2 D

Sub System Qual Readiness Review-ACD 1/2/03 2 6

Sub System Qual Readiness Review-TRKR 6/12/03 2 4

Sub System Qual Readiness Review-CAL 3/3/03 2 5

Sub System Qual Readiness Review-MECH 4/3/03 2 8

Sub System Qual Readiness Review-ELEC 12/5/03 2 7

Sub System Qual Review-ACD 3/31/03 2 6

Sub System Qual Review-TRKR 8/8/03 2 4

Sub System Qual Review-CAL 9/18/03 2 5

Sub System Qual Review-MECH 9/29/03 2 8

Sub System Qual Review-ELEC 1/22/04 2 7

Sub System Production Readiness Review-CAL 2/21/03 2 5

Sub System Production Readiness Review-TRKR 8/4/03 2 4




Level 3



Level III Milestones (3)Level III Milestones (3)vDE Activity


FinishDate

ND AV

Instrument Project Office (Level 3Mechanical Systems CDR 05/22/02* 2 8

Tracker CDR 05/29/02* 2 4

Calorimeter CDR 06/05/02* 2 5

Flight Software CDR 06/12/02* 2 7

Electronics & DAQ CDR 06/20/02* 2 7

Anticoincidence Detector CDR 06/26/02* 2 6

Science Analysis Software CDR 09/04/02* 2 D

IOC CDR 12/04/03* 2 B




Level 3



System Engineering CostSystem Engineering Cost

4.1.2

0

0.1

0.2

0.3

0.4

. . . . . . . . . . . . . . . . . . . . . . . .

FY00 FY01 FY02 FY03 FY04 FY05 FY06

$M

M & S ( no Travel )

Labor



System Engineering Cost & CommitmentsSystem Engineering Cost & Commitments



Systems EngineeringSystems Engineering

Supporting Materials



System Science Requirements (Continued)System Science Requirements (Continued)LAT Level IIb Requirements


(PDR)


9% at 100MeV Sim (TKR front and back separately, 20, 50, 100 MeV),BT (TPT from 5.2.1)

100 MeV – 10 GeV

8% at 10 GeV Sim (TKR front and back separately, 0.1, 0.2, 0.5, 1, 2, 5, 10 BT (TPT from 5.2.1)

<15% Sim (TKR front and back separately, 10, 50, 100, 300 GeV),BT (TPT from 5.2.1)

> 10 GeV <4.6% < 6% < 3 % Sim (60°, at 10, 50, 100, 300 GeV)

> 60° off-axis (Aeff > 10% that of NI)

(Aeff > 10% that of NI)

BT – beam test

NI – normal incidence

5.2.2

<= 10% < 8% 5.2.2

Energy Resolution

20 – 100 MeV <= 50%

5.2.2

5.2.2

10 – 300 GeV <= 20% < 15%

Comments:

TPT – tagged photon trigger

Energy Resolution vs. Energy

0

0.1

0.2

0.3

0.4

0.5

0.6

0.01 0.1 1 10 100 1000

Energy (GeV)

Ener

gy R

esol

utio

n (d

elta

E/E

) SpecGoalProposalPDR





(PDR)


3.37º Sim,BT (photons as in 5.2.1)

4.64º (Total) Sim,BT (photons as in 5.2.1)

.086º Sim,BT (photons as in 5.2.1)

.115º (Total) Sim,BT (photons as in 5.2.1)

Single Photon Angular Resolution (SPAR) – 95% On-Axis

2.1x/2.6x (front/back)

< 3x SPAR 68% On-Axis

< 2x SPAR 68% On-Axis

Sim (see cases for 68% On-Axis), BT (see Comments)

5.2.6

Single Photon Angular Resolution (SPAR) – 68% Off-Axis at 55°

1.6x < 1.7x SPAR 68% On-Axis

< 1.5x SPAR 68% On-Axis

Sim (averaged over f and at f = 0, 30, 45° ), BT (see Comments)

5.2.7

Single Photon Angular Resolution (SPAR) – 68% On-Axis

Comments:

10 – 300 GeV TKR Front

100 MeV TKR Front

5.2.5

< 0.3º

100 MeV TKR Back

10 – 300 GeV TKR Back

< 0.1º 5.2.5

< 0.15º < 0.07º

SPAR 68% Off-Axis at 55° – Bins of energy, angle, impact position and conversion layer TBD. This test drives the photon beam

SPAR 95% On-Axis – Need a factor > 20 statistics, or > 20k events in each energy/angle bin studied. This parameter must be carefully studied on the ground, as it parameter must be carefully studied on the ground, as it will be difficult to extract on-orb

BT – beam test

5.2.5

< 6.0º < 5.0º 5.2.5

< 3.5º < 3.0º

Angular Resolution vs. Energy

0.01

0.1

1

10

100

0.01 0.1 1 10 100 1000

Energy (GeV)

68%

On-

Axi

s C

onta

inm

ent A

ngle

SpecGoalPDR

LAT Front Only

LAT Back Only





(PDR)


Field of View (FOV) 2.4 sr > 2 sr > 3 sr Sim (same points as BT), BT (at least one energy in range 1 – 5 GeV at > 5 angles from 0 – 80°, using > 1000 TPTs in each bin

5.2.8

Source Location Determination

Source flux 10-7 ph cm-2 s-

1, E > 100 MeV, high gal. lat. source, spectral index -2 above flat background, no cutoff to 10 GeV and no s/c effects, 1 year survey

<0.4 arcmin < 0.5 arcmin (1σ radius)

< 0.3 arcmin (1σ radius)

Analysis (see Comments) 5.2.9

Point Source Sensitivity

> 100 MeV at high gal. lat., 1 year survey

< 3x10-9 cm-2 s-

1 < 6x10-9 cm-2

s-1 (5σ detection)

< 3x10-9 cm-2

s-1 (5σ detection)


Time Accuracy TBD < 10 µsec < 2 µsec BT (20±5 MeV, 100±10 MeV, 10±1 GeV photons or electrons)

5.2.11

Comments:

BT – beam tes t

Analys is us ing m easured, param eterized Aeff and SPAR functions with sky s im ulation.

Tim e Accuracy – Measure (event tim e s tam p – beam clock) dis tributions

Comments:

BT – beam testTPT – tagged photon trigger

Note: FOV is defined here as integral of effective area over solid angle, divided by peak (on-axis) effective area.

Relative Area vs. Angle of Incidence

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80

Angle of Incidence (°)

Effe

ctiv

e A

rea

/ On-

Axi

s Ef

fect

ive

Are

a Proposal

PDR





(PDR)


Dead Time <20 µsec < 100 µsec < 10 µsec Cosmic Ray Test (reducing CAL and TKR trigger thresholds to raise L1 rate to 10 kHz)

5.2.13

BT (electron and photon events from 100 MeV to 10 GeV and multi-electron events with effective energies up to 300 GeV)

Background Rejection

See Comments < 10% diffuse < 10% < 1% Sim (using best current background flux model), BT (TBD)

5.2.12

GRB Location Accuracy On-Board

Within LAT FOV, > 100 reconstructed photons with E > 1 GeV in 20 secs

TBD < 10 arcmin (1σ radius)

< 1 arcmin (1σ radius)


GRB Notification Time to Spacecraft

After detection of burst with characteristics as in 5.2.14

TBD < 5 sec < 2 sec Instrument/spacecraft simulator 5.2.15

AGN Location Accuracy On-board

Within LAT FOV at high gal. lat., with ∆F > 2x10-6 ph cm-2 s-1 (E > 100 MeV) for more than 1000 secs

TBD < 2° (1σ radius)


AGN Notification Time to Spacecraft


TBD < 1 min (after recognition)

Instrument/spacecraft simulator 5.2.17

Analysis using measured, parameterized Aeff and SPAR functions with sky simulation.

Background Rejection – evaluated as contamination of observed high lat. diffuse flux (1.5x10-5cm-2s-1sr-1) in any decade of energy (> 100 MeV), photon spectral index of -2.1 with no spectral cutoff

Comments:





PDR


GRB Location Accuracy On-Board

Within LAT FOV, > 100 reconstructed photons with E > 1 GeV in 20 secs

Comply < 10 arcmin (1σ radius)

< 1 arcmin (1σ radius)


GRB Notification Time to Spacecraft

After detection of burst with characteristics as in 5.2.14

Comply < 5 sec < 2 sec Instrument/spacecraft simulator 5.2.15

AGN Location Accuracy On-board


Comply < 2° (1σ radius)


AGN Notification Time to Spacecraft


Comply < 1 min (after recognition)

Instrument/spacecraft simulator 5.2.17

Comments:

Analysis using measured, parameterized Aeff and SPAR functions with sky simulation.



System RequirementsSystem RequirementsLAT Level IIb Requirements - Launch


(PDR)

Requirement Goal Verification Spec Ref.

Instrument Mass Excl. SI/SC I/F hardware

2673 kg < 3000 kg none Mass Properties Measurements

5.3.6

CG Constraints Measured from I/F plane

0.180 m < 0.246 m none Measure reaction torque with LAT on its side in integration fixture

5.3.7

Envelope Delta II Payload Planners Guide

x: 1.794 my: 1.794 mz: 1.044 m

x: < 1.8 my: < 1.8 mz: < 3.15 m

none Survey LAT 5.3.8

Static Load Launch config. comply See SI/SC IRD* none Structural analysis and inspection/ func. test after exposure

5.3.12.4

Random Vibration Launch config. comply GEVS Table D-6* none Structural analysis and inspection/ func. test after exposure

5.3.12.5

Acoustic Loads Launch config. comply GEVS Table D-3* none Structural analysis and inspection/ func. test after exposure

5.3.12.6

Shock Launch config. comply GEVS Table D-8 or D-9 as appl.**

none Structural analysis and inspection/ func. test after exposure (S/C-level test)

5.3.12.7

Launch Temperature Launch config. comply 0° < T < 30° C none T/V and thermal modelling

5.3.12.8

Launch Pressure Launch config. comply Tolerate launch pressure profile in Delta II PPG, Sec. 4.2.1

none Venting Analysis 5.3.12.9

Comments:*Pending change**Levels attenuated to LAT-SC interface values



System Requirements (Continued)System Requirements (Continued)LAT Level IIb Requirements – Flight Operations


(PDR)


Instrument Life Time on-orbit > 10 years > 5 years > 10 years Reliability Analysis 5.3.2

Science Data Interface

comply MIL-STD-1553 none Interface test with S/C simulator

5.3.3

SI/SC Communications

comply MIL-STD-1553 none Interface test with S/C simulator

5.3.4

Operating Modes comply See MSS, Sec. 3.1.13 (accommodate mission modes: sky survey, pointed observation, safe, load shed)

none LAT operational and T/V tests

5.3.5

Average Power Averaged over 24 hrs. 528 watts < 650 watts none Power consumption measurements and analysis

5.3.10.1

Peak Power 602 watts < 1000 watts none Power consumption measurements and analysis

5.3.10.2

Peak Power Duration Per orbit comply < 10 minutes none Analysis 5.3.10.3

Heat Dissipation comply Dissipate all internally generated heat in addition to thermal flux

none T/V and thermal modelling. T/B test.

5.3.11.1

Heat Load from S/C Excl. radiated heat from S/C to radiators

comply Dissipate up to 5 watts conducted heat from S/C.

none Thermal analysis 5.3.11.2



System Requirements (Continued)System Requirements (Continued)LAT Level IIb Requirements – Flight Operations


(PDR)


comply Earth IR: 265 W/m2 (hot) 208 W/m2 (cold)

comply Albedo factor: 0.40 (hot) 0.25 (cold)

Solar Thermal Flux Environment

Any operational mode, LAT radiator temperatures

comply 1419 W/m2 (hot) 1286 W/m2 (cold)

none T/V and thermal modelling

5.3.12.10.2

Solar Panel Backloading

Any operational mode, LAT radiator temperatures

comply TBD W/m 2̂ on +Y or –Y side of LAT. One side exposed at a time.


5.3.12.10.3

Radiator Sun Exposure

Any operational mode, LAT radiator temperatures within operational

comply Up to 5 degrees view angle to the sun from radiator. One side exposed at a time.


5.3.12.10.4

Survival Solar Thermal Flux

Powered off, prolonged exposure on any

comply 1419 W/m2 (hot) 1286 W/m2 (cold)


5.3.12.10.5

Meteoroid and Debris Flux

Any operational mode

comply to 0.001 Tolerate impact by meteoroids/debris with probability of impact of 0.001 and above. See MSS, Sec

none Probabilistic risk analysis and shield impact damage analysis

5.3.12.12

5.3.12.10.1Earth IR and Albedo Flux Environment

Any operational mode, LAT radiator temperatures within operational




System Requirements (Continued)System Requirements (Continued)LAT Level IIb Requirements – Ground Operations

Ground Temperature - Unpowered

Powered off comply* Tolerate 0 < T < 40 °C

none thermal cycle test, monitor temperatures, func. test after extended storage and transport.

5.3.12.3.1

Ground Rel. Humidity -Unpowered

Powered off comply* Tolerate 20% < R.H. < 55%

none monitor humidity, func. test after extended storage and transport.

5.3.12.3.2

I&T Temperature Any operational mode comply* Tolerate 15 < T < 25 °C

none thermal cycle test, monitor room temp. and func. test at ambient

5.3.12.3.3

I&T Rel. Humidity Any operational mode comply* Tolerate 35% < R.H. < 55%

none monitor room humidity and func. test at ambient

5.3.12.3.4

Ground Temp. Rate of Change**

Any operational mode comply* Tolerate up to 5° C/hour

none thermal cycle test 5.3.12.3.7

Launch Vehicle Temp.

Any operational mode comply* Tolerate 13° < T < 27° C

none Included in thermal cycle test range

5.3.12.3.5

Launch Vehicle Rel. Humidity

Any operational mode comply* Tolerate 40% < R.H. < 55%

none Included in thermal cycle test range

5.3.12.3.6

*Will comply by design or procedure. The instrument must tolerate this environment or the LAT project must develop procedures and equipment to protect the instrument during ground operations.**To protect the CsI logs.

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