GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 1 GLAST Large Area Telescope: Electronics, Data Acquisition & Instrument Flight Software Power, Grounding & EMI March 19-20, 2003 David Nelson Stanford Linear Accelerator Center (650) Gamma-ray Large Area Space Telescope

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 2 Summary –Overview –Requirements –Space Power Interface –Power Allocation –Power Distribution Module –Tower Power Supply Module –Grounding –EMI/EMC –EMI Allocation –Verification & Test –Summary

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 3 Overview Grounding & Shielding GRID Added Cal Base plates Added T&DF TEMs Added T&DF TEM Power Supplies Added T&DF PDU, GASU, CPUs Added X-LAT plates & RF shields

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 4 Requirements Documents –LAT-SS Level III Power Systems Specifications –LAT-SS Level IV Tower Power Supply Specifications –GSFC 433-RQMT-0005 EMI Requirements –NASA-HDBK Electrical Grounding Architecture for Unmanned Spacecraft –LAT-SS LAT Grounding & Shielding –LAT-SS GLAST LAT Grounding & Shielding Interface Control Documents (ICD)

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 5 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

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 6 Power Allocation QuantityColdCurrent Hot Case CaseEstimateAllocation Total Mech On-Board Power TEM--Tower Electronics Module TEM board Power Supplies TKR,CAL,TEM GASU--Global Tgr ACD, Signal Dist. Unit EP, AEM, Sig Dist & Supplies Other Boxes SIU--Spacecraft Interface Unit EPU Total EPU--Event Processor Unit PDU--Power Distribution Unit

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 7 LAT Power Distribution TKR: Tracker CAL: Calorimeter ACD: Anti-Coincidence Detector EPU: Event Processor Unit SIU: Spacecraft Interface Unit GAS Unit: Global Trigger- ACD-Signal Distribution Unit PS Board: TEM Power Supply DAQ Board: TEM DAQ Board PDU: Power Distribution Unit

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 8 Power Allocation Example: SIB Courtesy of Dennis Silver, Silver Engineering

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 9 Power Distribution in PDU Discrete signal from SIU selects which SC main power to use 28V/3.3V PDU converter is powered when SC Main feed is powered Discrete signal from SIU turns on power to GASU prime or redundant DAQ board PDU FPGA controls power switches for TEM’s, EPU’s, and ACD supplies in GASU Power switches are implemented with PMOS transistors ICD: LAT-SS and LAT- SS Status: layout started of flight-board model

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 10 Tower Power Supply Module

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 11 Tower Power Supplies Tower Supply converts 28V to the following: Supply TypeVoltage, VCurrent, AmpPower, W CAL-Analog CAL-Digital CAL Bias50 to 100 adj TKR-Analog TKR-Analog TKR -Digital TKR Bias50 to 150 adj TEM -Digital

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 12 Tower Power Development Engineering model tower power supply built and used in EGSE test-stands at SLAC, NRL, GSFC, Italy –Flight like interfaces and functionality

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 13 Tower Power Flight Proof-of-Principle Power Supplies –Received and evaluated most challenging converter: 28V-1.5V supply for TKR Designed at vendor Uses synchronous rectification to meet efficiency requirement (measured 78%) Built mostly with flight- components Noise performance: 500  V Evaluated with TKR electronics, no increase in noise observed Status: –Tower supplies out for bids –RFP expected back March 25, 03 –Statement of Work: LAT-SS –ICD: LAT-TD-01281

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 14 SHIELDING

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 15 Grounding & Shielding LAT RF SHIELD BOX ENCLOSURE

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 16 EMI/ EMC & EMI Allocation Primary document 433-RQMT-005 Radiated Emissions (RE101, RE102) –20% of total emissions are allocated to subsystems outside LAT RF shield ACD, Tracker, Heaters –60% of total emissions are allocated to subsystems inside LAT shield Radiated Susceptibility (RS101,RS103) –All subsystems must meet Section 5.3 of 433-RQMT-005 Conducted Emissions (CE101, CECM) –Only the T&DF subsystem is affected and must meet requirements Conducted Susceptibility (CS101, CS116) –Only the T&DF subsystem is affected and must meet requirements

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 17 Verification & Test

GLAST LAT ProjectDOE/NASA Peer Critical Design Review, March 19-20, 2003 D. Nelson 18 Summary Engineering models of main supplies (tower power supplies) built and are used in 16 EGSE test sets in collaboration Flight model out for RFP, to be awarded end of March 03 Grounding and EMI plan in place