GLAST Large Area Telescope: Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Electronics, Data Acquisition & Flight Software LAT Electronics Design Engineering Gunther Haller Stanford Linear Accelerator Center Manager, Electronics, DAQ & FSW LAT Chief Electronics Engineer haller@slac.stanford.edu (650) 926-4257

LAT Electronics Physical TKR Front-End Electronics (MCM) ACD Front-End Electronics (FREE) CAL Front-End Electronics (AFEE) TKR 16 Tower Electronics Modules DAQ electronics module (DAQ-EM) Power-supplies for tower electronics CAL Global-Trigger/ACD-EM/Signal-Distribution (GAS) Unit* 3 Event-Processor Units (2+1 spare) Event processing CPU LAT Communication Board (LCB) Storage Interface Board (SIB) Spacecraft Interface Unit Storage Interface Board (SIB): EEPROM SC 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 * Primary & Secondary Units shown in one chassis

LAT Electronics TKR: Tracker CAL: Calorimeter ACD: Anti-Coincidence Detector EPU: Event Processor Unit SIU: Spacecraft Interface Unit GAS Unit: Global Trigger-ACD-Signal Distribution Unit TEM: Tower Electronics Module There are 2 prim EPU’s, 1 redundant EPU (not shown) 1 prim SIU, 1 redundant SIU (not shown) 1 prim GAS, 1 redund. GAS (not shown) 1 prim PDU (not shown), 1 redundant PDU (not shown)

Tracker Electronics TKR sub-system electronics Si-Strip Detectors GTRC ASIC GTFE ASIC TKR sub-system electronics Si-Strip Detectors 24 GTFE (GLAST Tracker Front-End) ASICs (1,536 signal channels) 2 GTRC (GLAST Tracker Readout Controller) ASICs MCM (Multi-Chip Module) Flex-cables Presented in tracker sub-system presentation

Calorimeter Electronics GCRC ASIC GCFE ASIC CAL sub-system electronics Diodes 48 GCFE (GLAST Calorimeter Front-End) ASICs 4 GCRC (GLAST Calorimeter Readout Controller) ASICs AFEE (Analog Front-End Electronics) board Presented in calorimeter sub-system presentation

ACD Electronics ACD sub-system electronics PMT’s 18 GAFE (GLAST ACD Front-End) ASICs 1 GARC (GLAST ACD Readout Controller) ASIC FREE (Front-End Electronics) board High-Voltage Supply board (not shown) Presented in ACD sub-system presentation GAFE ASIC GARC ASIC

DAQ Electronics DAQ sub-system electronics SIU, EPU, GASU, PDU, TEM, Harness, Instrument Software Example shown is Tower Electronics Module Engineering Unit Presented in DAQ & Instrument Software presentations

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

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 (renamed SIB to Storage Interface Board) 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.

LAT Spacecraft Interface Power (to SIU, PDU, Heaters) 28V regulated and unregulated MIL1553 (to/from SIU) Commanding, house-keeping Science Interface (from GASU) Transport of science data to spacecraft solid-state recorder 1-PPS timing signal (to GASU) Timing pulse GBM GRB Candidate signal (to GASU) Notification of candidate Gamma-Ray Burst (GRB), from GBM routed through SC Discretes (to/from SIU)) Pulsed and level digital signals from and to spacecraft Analog Monitoring (from entire LAT) Temperature and voltage monitoring by SC; available even when LAT is off Two sets of power & signals: Prime and redundant Spectrum Astro SC-LAT Interface Document

Power Interface to Spacecraft All power feeds from spacecraft can be turned off/on via ground Heaters are on separate power feeds Each SIU is powered via one dedicated SC power feed Rest of LAT power is on main feed One primary, one redundant Cross-connected in LAT PDU Can use either SC main feed to power either PDU Spacecraft turns off SIU/DAQ feeds when going to survival mode LAT start-up ICD: LAT-TD-01536 Describes process of cold and warm boot (bring-up) of LAT

Spacecraft 1-PPS and GRB Candidate Signal (to GASU) 1-PPS signal from spacecraft (prime and redundant) are connected to both GASU boards (prime and redundant) GASU selects which SC signal to use Result is fanned out to all processor crates (SIU’s as well as EPU’s) prime and redundant signals are connected to discrete RAD750 processor inputs (PID’s) Software select which 1-PPS to use SC-LAT components are fully cross-connected Same for GBM GRB candidate signal LAT needs to know which SC-port or GBM-port to listen to Ground commanding

Spacecraft Discrete Signals & MIL1553 (to SIU) Discrete Signals from SC to LAT: Discrete LVDS-signals from spacecraft prime and redundant are connected to both SIU crates (prime and redundant) Reset discrete: P and R SC signal is logically Or’ed and used as CPU reset Spare discretes: CPU selects whether to use P or R input and result is routed to CPU discrete inputs (3 prime and 3 redundant) Discrete Signals from LAT to SC (not shown) Discrete LVDS-signals from LAT SIU P and SIU R are driven to both, prime and redundant, spacecraft C&DH (Control & Data Handling) systems MIL1553 Command/Data (not shown) Command & Data interface to both, SIU P and SIU R

LAT-SC Science Interface (from GASU) GASU event builder Directs data from TEM’s to any of the CPU’s (not shown) Directs data from CPU to CPU Directs data from CPU to spacecraft Any CPU can direct data via either GASU Event-Builder (P or R) to SC Data is driven to both SC sections (P and R) SC needs to select which GASU to listen to LAT GASU needs to know which SC port (P or R) flow-control line is active All configured via ground commanding

Connections LAT/Spacecraft and to LAT EMI Shield ACD HTR EGSE EPU SIU P GASU PDU SIU R TEM HTR LAT EMI shield Heater & Monitoring Box Spacecraft

Grounding and Shielding EMI/EMC: GSFC-355-RQMT

Shielding

Power Allocation Quantity Cold Current Hot Case Case Estimate   Quantity Cold Current Hot Case Case Estimate Allocation Total 286.20 313.79 318.00 359.85 Mech On-Board Power 1 38.00 35.00 TEM--Tower Electronics Module 43.20 46.70 48.00 54.32 TEM board 16 2.70 2.92 3.00 3.39 Power Supplies 148.50 163.29 165.00 186.72 TKR,CAL,TEM 9.28 10.21 11.67 GASU--Global Tgr ACD, Signal Dist. Unit 19.80 22.37 22.00 24.90 EP, AEM, Sig Dist & Supplies Other Boxes 74.70 81.43 83.00 93.92 SIU--Spacecraft Interface Unit 21.60 23.89 24.00 27.16 EPU Total 38.70 42.60 43.00 48.66 EPU--Event Processor Unit 2 19.35 21.30 21.50 24.33 PDU--Power Distribution Unit 14.40 14.93 16.00 18.11

Monitoring Spacecraft monitors Voltages & Temperatures PDU, SIU, GASU, VCHP switches Temperatures Locations outside LAT EMI shield PDU monitors TEM, EPU, SIU GASU monitors ACD TEM monitors CAL, TKR

Temperature Monitoring (SC & PDU) Location of Sensor Sensor Type Sensors by processed Spacecraft PDU Prime Redundant ACD Tiles Thermal 5   ACD TSA Shell (inside) ACD TSA Shell (outside) 2 ACD BEA-Grid interface ACD PMT Rail 4 Calorimeter Baseplate 16 SIU EPU 3 GASU TEM DAQ Board TEM pwr Supply Radiator Anti-Freeze Htr Radiators 8 10 Grid-Radiator interface Grid Make-up Heaters VCHP-XLHP interface 12 X-LAT Plate VCHP-DSHP interface Grid VCHP's Reservoir Htr 24 VCHP Reservoir Htr Pri/Sec Voltage Spare Temp. Channels SC Action if low or high limit is reached

Temperature Monitoring (TEM & GASU) Sensor processed by Location Sensor Type TEM GASU Prime Redundant ACD FREE Thermal   12 CAL AFEE 128 AEM Power Supply 1 AEM DAQ Board TKR Cables 256 LAT Instrumentation Plan: LAT-SS-00890 Spacecraft ICD: GSFC-IRD-433

Voltage/Current Monitoring Location Sensor Type Sensed by Spacecraft Sensed by PDU Sensed by TEM Sensed by GASU Prime Redundant VCHP Reservoir Htr Pri/Sec Voltage 4   SIU Pri/Sec 3.3/5V V 2 PDU Pri/Sec 3.3V V GASU Pri/Sec 3.3/28V/3.3VA V 6 EPU 3.3V V TEM 3.3V V 16 ACD FREE V 12 ACD FREE I Current 1 ACD HV (I) 24 TKR V 64 TKR I CAL V 48 CAL I TEM DAQ V TEM DAQ I LAT SIU Bus V Pri/Sec LAT VCHP Bus V Pri/Sec Spare Voltage Channels 18 Total 32 20 256 43 Note: LAT does not monitor currents or voltages on SC-LAT feeds

Heater Control Survival Heaters (GRID & VCHP Anti-Freeze) Powered by SC unregulated feed Block redundant prime and redundant set Thermostat control, not controlled by LAT electronics Survival & Operational Heaters (VCHP) Powered by SC regulated feed Block redundant prime and redundant set of 12 heaters Controlled by LAT SIU Temperature monitoring Software algorithm in CPU 12 hardware switches in SIB Hardware watchdog to power heaters as default Final responsibility of not exceeding low or high survival temperatures lays with SC LAT-SS-00715 Thermal Control System ICD

Instrument Protection: High and Low Temperatures GRID/Anti-freeze heaters turn on when T is below thermostats no LAT active control VCHP heaters LAT responsible for operational control Survival T if T too high or too low SC puts LAT into safe mode SC turns-off LAT SIU and Main DAQ power SC may need to switch heater feeds in cold case SC responsible for LAT Document: LAT-TD-01553

Instrument Protection: ACD PMT Protection LAT turns down PMT high-voltage levels during SAA passage to protect PMT’s In response to SC SAA notification, or When SC heard-beat is lost PMT’s are hardware protected within ACD in case of DAQ mishap ACD HV supplies have built-in protection to limit current to PMT’s Document: LAT-TD-01553

Instrument Protection: Over-Current LAT does not monitor current on SC feeds SIU power feed not fused on LAT, SC has current limit switch Main DAQ feed power not fused on LAT, SC has current limit switch LAT PDU distributes 28V to about 20 LAT loads. Each sub-feed is fused on PDU via poly-switches Tower Electronics Modules convert and distribute power (+1.5V, 2.5V, 3.3V, 0-100V, 0-150V) to TKR & CAL: Feeds are fused on TEMs via poly-switches

Summary Interface to SC defined Grounding and shielding of LAT defined Monitoring of temperatures, voltages, and currents defined Heater control defined Instrument protection tree documented SC, not LAT has final responsibility to protect instrument from damage in respect to temperatures SC has to meet power quality specifications to not damage LAT LAT is responsible for SAA PMT survival First layer of protection software controlled Second layer (back-up) protection: hardware Over-current protection of electronics components via poly-fuses