1. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 1 GLAST Large Area Telescope: Electronics, Data Acquisition & Flight Software System Engineering Gunther Haller Stanford Linear Accelerator Center Manager, Electronics, DAQ & FSW LAT Chief Electronics Engineer haller@slac.stanford.edu (650) 926-4257 Gamma-ray Large Area Space Telescope

2. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 2 System Engineering Outline System Overview Changes since PDR External Interfaces Internal Interfaces Technical Budget Verification & Test Risk FMEA Reliability Allocations Parts and Spares Plan Drawing Tree

3. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 3 Data-Acquisition (DAQ) System Overview Configuration, triggering, event-flow control and readout, monitoring, and supply of power to –16 Calorimeter and Tracker towers with a total of 850,000 tracker channels and 3,000 calorimeter channels –12 ACD front-ends with a total of 208 ACD channels Interface to spacecraft for control, data, monitoring, and power Trigger system (hardware selection of possibly interesting events) Event filtering Housekeeping Operational thermal control

4. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 4 LAT Electronics Hierarchy Tower Electronics Module –Interface to calorimeter and tracker on each tower –Monitoring –Combination of sub-system trigger signals to primitives –Event buffering GAS Unit –Command-response unit receives and distributes command, clock, and data –Global trigger unit generates LAT-wide readout decision signals based on trigger primitives from TEM’s and ACD –Event-builder unit builds complete LAT events out of asynchronous event-fragments; Forward complete events to dynamically selected target EPU’s or spacecraft –ACD electronics module tasks much like TEM for TKR/CAL EPU: Event processor unit runs filter algorithm to reduce 10kHz input event rate down to 30 Hz (with two EPU’s) SIU: Spacecraft interface unit controls LAT and interfaces to spacecraft Instrument software runs on EPU and SIU processors only Power system not shown

5. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 5 LAT Electronics Physical 16 Tower Electronics Modules –DAQ electronics module (DAQ-EM) –Power-supplies for tower electronics * Primary & Secondary Units shown in one chassis 3 Event-Processor Units (2+1 spare) –Event processing CPU –LAT Communication Board –SIB Spacecraft Interface Unit –Spacecraft Interface Board (SIB): Spacecraft interface for MIL1553 control & data –LAT control CPU –LAT Communication Board (LCB): LAT command and data interface Power-Distribution Unit (PDU)* –Spacecraft interface, power –LAT power distribution –LAT health monitoring Global-Trigger/ACD-EM/Signal-Distribution Unit* TKR CAL TKR Front-End Electronics (MCM) ACD Front-End Electronics (FREE) CAL Front-End Electronics (AFEE)

6. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 6 Changes since PDR Spacecraft Selection and Meetings: –PDU was moved to opposite side of SIU to match SC power/C&DH physical partitioning –Signal levels (discretes, 1 PPS, Science Interface, GBM GRB signal) were officially changed to LVDS (before undefined or RS422), March 03 –Recently finalized power, analog monitoring, and discrete interface to SC –Defined MIL1553 command set/interface –Separated SIU prime and redundant into separate (and identical) crate assemblies since cross-connection to SC prime and redundant was solved on the SC- LAT interface level and lead to removal of direct SIU-SIU inter- connections Before SC selection After SC selection

7. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 7 Changes since PDR (Con’t) Event-Builder was moved from CPU crates to GAS unit –Reduced complexity of inter-connections –Reduced hardware from 3 event-builder blocks to 2 (1 prime, 1 redundant), and power dissipation from two event-builder blocks to one SIU crate was modified to be the same as EPU crate –Removes mechanical, thermal, electrical design effort for one assembly –Moved SC science interface from Spacecraft Interface Board in SIU to event-builder in GASU –Additional benefit that SIB board is almost identical to existing SECCI version (both boards are designed by NRL/Silver Engineering), major simplification –Science interface on GASU is small change since GASU already transmits event data to LAT CPU’s, so additional target is incremental –Added SIB board in each EPU crate to provide local EEPROM Simplification in software effort. No remote booting code development/testing required.

8. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 8 External Interfaces InterfaceDocumentStatus CalorimeterLAT-SS-00238released TrackerLAT-SS-00176released ACDLAT-SS-00363released Mechanical/ThermalLAT-SS-01794in progress SpacecraftGSFC-433-IRDin progress at GSFC but content stable All external DAQ interfaces released with the exception of spacecraft interface and mechanical/thermal interface (mainly to X-LAT plate)

9. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 9 Internal Interfaces InterfaceDocumentStatus Tower Electronics ModuleLAT-TD-00605finalizing TEM Power-Supply UnitLAT-SS-01281finalizing GAS UnitLAT-SS-01544 LAT-TD-00639 LAT-TD-01545 LAT-TD-01546 LAT-TD-01547 finalizing SIU/EPULAT-SS-01539finalizing PDULAT-SS-01542finalizing VCHP Control UnitLAT-SS-00715finalizing All internal interfaces are final, documents are being updated, release before CDR

10. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 10 DAQ Technical Budget Summary Technical Resources DAQ Mass –Sub-system allocation: 220 kg –Detailed estimate: 199.3 kg DAQ Power –Subsystem allocation: 318 W –Detailed estimate: 313.8 W CPU Cycles –Allocation: 2 CPU’s –Detailed estimate: < 1 CPU For detailed breakdown see Power/Mechanical/Software presentations

11. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 11 Verification & Test Hardware and software development closely integrated –Design of hardware versus software complexity optimized continuously –Software runs with LAT engineering model electronics –Continuous hardware versus software verification –Full system including sub-system electronics from and at other institutions –Independent verification process Exchange of hardware and software -> –ACD hardware, TKR hardware, CAL hardware –DAQ hardware –Flight software, I&T software –ACD Scripts, TKR scripts, CAL scripts, DAQ scripts –No integration at flight- LAT integration stage of components which have not operating fully integrated in earlier stages Exception is spacecraft, since simulator is only simulating and is not real hardware/software Model Development DesignHardwareFabTest Design/DevelopDevelop/TestFormal TestSoftwareRelease to I&T

12. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 12 Verification & Test (Con’t) Three development cycles –Engineering Model 1 Single tower, single CPU –Engineering Model 2 Multiple tower, single CPU –Flight Model Multiple towers, multiple CPU’s Peer-Reviews after end of each development cycle In addition regular LAT reviews (Manufacturing Readiness Review, etc) Development Cycles EM 1 EM2 Release to I&T FU Release to sub-systems

13. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 13 Verification Matrix (Doors Example Page) IDTDF L3 Performance SpecificationVMVerif. TDF3-7The Level 1 Trigger (L1T) system shall be used to detect an interesting event and provide a signal to the detector subsystems to capture and read out the event data. Demo TDF3-105The trigger (TRG) system shall determine whether the event is interesting based on trigger input signals received from the detector systems. Demo TDF3-9The L1 trigger system shall accept trigger inputs from the ACD, TKR, CAL and dataflow subsystems. Demo TDF3-11The L1 trigger system shall time-align trigger inputs from the ACD, TKR, CAL and dataflow subsystems to a precision better than 100 ns. Test TDF3-13The L1 trigger system shall implement multiple overlapping triggers to allow cross-trigger monitoring. Test TDF3-15The L1 trigger logic shall generate a trigger acknowledge signal (L1TACK) and a trigger type (e.g. CNO) for distribution to the subsystems. Demo TDF3-17The L1 trigger logic shall generate the Trigger Acknowledge output with a latency of less than 1.3 mus. Test TDF3-106The latency from the time the particle traverses the LAT to when the input signals need to be recorded at the earliest shall be 2 ms. Test TDF3-19 The L1 trigger contribution to the overall trigger jitter shall be less than ± 50 ns. Test TDF3-107 The overall trigger jitter for the LAT shall be ± 200 ns. Test TDF3-51 The dataflow system shall reduce the event rate accepted by the L1T to an output rate commensurate with the spacecraft interface as specified in 433-IRD-0001, keeping events meeting the science objectives. Demo

14. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 14 Test Matrix Applies to each board and assembly. In this slide the tests at each level are listed

15. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 15 Electrical & Environmental Test Flow Qual Elec Sine Vibe Random Vibe Thermal Vac EMI/EMC Accept Elec Static Load Random Vibe Thermal Vac TEM DAQ Qual Elec Sine Vibe Random Vibe Thermal Vac EMI/EMC Accept Elec Static Load Random Vibe Thermal Vac TEM PS Qual Elec TEM DAQ/PS Accept Elec Qual Elec Sine Vibe Random Vibe Thermal Vac EMI/EMC Accept Elec Static Load Random Vibe Thermal Vac GASU LAT Qual LAT Test Accept LAT Test PDU SIU EPU

16. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 16 Risk No single DAQ system failure can degrade LAT Electronics capabilities below minimum science requirements Failure in SIU, PDU, or GASU can require use of the respective redundant unit Failure in one of the two EPU’s can require use of the redundant EPU unit. A second failure will reduce the available EPU CPU power by a factor of 2. Failure in TEM power-supply or TEM DAQ module can lead to –Loss of a full tower (most of the assembly is single string) –Loss of the calorimeter or parts of it –Loss of the tracker or parts of it

17. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 17 Electronics Risk Summary ID #Risk RankRisk DescriptionRisk Mitigation Elec/224Moderate Flight-Software schedule is tight Depends on execution of LAT software development approach. Delays in incremental review process may impact cost & schedule Detailed software development plan, schedule and review points established (3/24/03). Early integration of software to target hardware via EM plan (Sept 03) Extensive use of test bed (Feb 04 and beyond) Elec/221Moderate Tower Power Supplies Cost & Schedule depend on bids received in response to RFP Proposals may exceed allocated schedule & funding Bids expected 3/25/03 Assess schedule problem Determine cost impact to maintain schedule Negotiate with vendor to minimize impact Develop minimum impact re-plan & pursue CCB approval

18. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 18 Electronics Risk Summary ID #Risk RankRisk DescriptionRisk Mitigation Elec/223Low Two types of Tower Electronics Module ASICs submitted 1/18/03. 3 month turn around results in late reaction required if flaw is found upon delivery and test resulting in schedule and cost impact Protect schedule for additional ASIC run. Evaluate work arounds to mitigate late delivery of flight ASICs and recover schedule margin. If untenable ASIC flaws occur, implement worst case backup (FPGAs) Elec/222Low Cost & Schedule of CPU Board depend on bids received in response to RFP to be sent out end of Mar-03. Bidding cycle 4-weeks For now NRL CPU board effort is stopped. If there is a problem with the BAE board, would revive the effort

19. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 19 FTA’s completed on EPU’s, GASU’s, PDU’s, SIU’s, TEM’s, & TEM/PS’s No single point failures without ground contingency – (Software) Most components multiply redundant (More than one redundant component) Non-redundant with in redundant systems identified. Fault Tree Analysis – LAT-TD-01757-01 (Draft) Failure Mode & Effects Analysis - LAT-TD-00374-01 (Being Drafted) Failure modes identified Effects analysis underway Probability being linked to component failure No criticality 1, or 2 failures Few 2R failures, mostly 2MR thru 5 failuresFMEA

20. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 20 Reliability Allocation Observatory 85% (Pf =.15) Mission 70% (Pf =.3) LAT 85% (Pf =.15) DAQ 96% (Pf =.04) Tower Electronics TEM DAQTEM PS GASUPDUSIU SIBLCBPSBCPU incl FSW HarnessEPU Back Plane

21. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 21 Parts Lists –Electrical component list for DAQ submitted to Electrical Parts Control Board and most parts are approved (see later presentation) –Mechanical components list for DAQ submitted to Mechanical Parts Control Board

22. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 22 Spares Plan ItemNeed for Flight QualFlight Spares Spare PCI boards Tower DAQ Module Assembly1612*n/a Tower Power Supply Module Assembly1611*n/a GASU Assembly (contains prime and redundant unit)110*n/a PDU Assembly (contains prime and redundant unit)110*n/a SIU Assembly210*CPU/SIU- SIB/PSB/LCB EPU Assembly30**0*EPU-SIB * Qualification Models are flight spares ** EPU does not have separate qualification since crate is the same as SIU crate

23. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 23 Technical Issues and Status No known technical issues in respect to functionality and performance except potentially –TEM GTCC and GCCC ASIC (back from fabrication end of 3/03) –Reliability; Analysis in progress

24. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 24 Drawing Tree (Example)

25. GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 G. Haller 4.1.7 Elex System Engineering V7 25 Summary Changes since PDR described Interfaces documents released and under change control Technical budget at CDR level with sufficient margin Verification and test plans documented Risks contained in LAT database with mitigations FMEA and reliability well under way Drawing tree well advanced System engineering will be at CDR level by CDR time –Main remaining item is completion of reliability analysis