09 EMI

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GLAST Large Area Telescope LAT Pre-Shipment Review EMI/EMC Neil Johnson NRL Michael Lovellette NRL Stanford Linear Accelerator Center


Purpose / Contents Demonstrate readiness to proceed with EMI/EMC testing of the integrated flight instrument, i.e. the LAT: Test requirements are complete LAT has been appropriately tested at lower levels of assembly Passes comprehensive systems test EMI/EMC test plans and procedures complete Facilities readiness and certification verified STE and MGSE complete, fabricated, and ready for use Manpower is sufficient to cover all planned for activities


Requirements complete All flight system design analyses and unit testing have been successfully completed Mission System Spec  433-SPEC-0005 EMI Environments LAT Environmental Requirements Spec  LAT-SS-00778 EMI Environments LAT Performance Verification Plan  LAT-MD-00408-04c Verification test definition EMI Test Plan  LAT-MD-0027261-01 LAT EMI-specific operating modes have been defined LICOS scripts and supporting displays are in development

Subsystem EMI/EMC Test Summary: 

Subsystem EMI/EMC Test Summary

Radiator Subsystem EMI/EMC Issue: 

Radiator Subsystem EMI/EMC Issue VCHP heater Radiated Emissions testing S/C power source for LAT VCHP heaters is an unfiltered DC-DC converter. Concern is the conducted noise for this power source will become radiated emission issue for LAT system test. This issue shall be resolved by special subsystem (Radiator) test – RE102 – using simulated S/C power source. The test will be performed just prior to LAT system EMI/EMC test. Preliminary testing of this at SLAC gives reasonable confidence that there is no significant issue here.

LAT EMI Test: 

LAT EMI Test LAT test levels derived from LAT-SS-0778 Test Suite: CE102 Conducted Emissions, Power Leads, 10 kHz to 10 MHz, MIL-STD-462, CE03 CECM Conducted Emissions, Time Domain, 150 MHz Bandwidth CS102 Conducted Susceptibility, Power Leads, 10 kHz to 10 MHz, MIL-STD-462, CS02 CSCM Conducted Susceptibility, Common Mode, 30 Hz to 150 MHz, MIL-STD-462, CS02 CS06 Conducted Susceptibility, Spike, Power Leads, MIL-STD-462 RE101 Radiated Emissions, Magnetic Field, 20 Hz to 50 kHz RE102 Radiated Emissions, Electric Field, 10 kHz to 18 GHz, MIL-STD-461E RS101 Radiated Susceptibility, Magnetic Field, 20 Hz to 50 kHz RS103 Radiated Susceptibility, Electric Field, 30 MHz to 18 GHz Verify by Analysis: RS103 Radiated Susceptibility, Electric Field, 18 GHz to 40 GHz Static Magnetic Field

LAT Power Interfaces: 

LAT Power Interfaces SC-LAT Power Interfaces SC PRU (P) - LAT PDU SC PRU (R) - LAT PDU SC PRU (P) - LAT SIU (P) SC PRU (R) - LAT SIU (R) SC PRU (P) - LAT VCHP +Y Heaters SC PRU (P) - LAT VCHP –Y Heaters SC PRU (R) - LAT VCHP +Y Heaters SC PRU (R) - LAT VCHP –Y Heaters SC PRU (P) - LAT Makeup Heaters (Survival) SC PRU (R) - LAT Makeup Heaters (Survival) Heater circuit power interfaces are not tested.

Test Limitations: 

Test Limitations RS103 upper limit of 18GHz (40GHz) 18 – 40 GHz addressed by analysis. Limited area of RS101 test Requires scanning each 10cm x 10cm area, ~16min/scan ~1450 scans for the LAT, another ~1200 for the radiators (~29 days) Scan selected locations around connectors, PMTs, BEA Limited R (redundant) side conducted testing Emissions tests and susceptibility only where noted on Primary side

EMI Test Configuration: 

EMI Test Configuration Performed in NRL anechoic chamber ESD bags will be removed during active testing. Bags in place for transport and inactive periods. GN2 purge to control humidity Active cooling w/ LAT chiller system Path finder of LAT instrument on the test stand in NRL’s anechoic chamber

Test Layout: 

Test Layout LAT Chiller Connection

Conducted Test Considerations: 

Conducted Test Considerations Fully test Primary: SC PRU (P) - LAT PDU (P) SC PRU (P) - LAT SIU (P) Limited test of Redundant: (as a result of Primary findings) SC PRU (R) - LAT PDU (R) SC PRU (R) - LAT SIU (R) No plan to test PRU - LAT Survival Heaters Thermostatic control, open circuit at LAT operating temp Not active with LAT operating in Mission No plan to test PRU - VCHP Heaters

Test Harnesses: 

Test Harnesses Radiated testing will used nominal EGSE cables Harness is fully shielded Includes all connector savers Any test ports are closed out or have shielded harnesses Test harnesses are shielded Accelerometers TCs & thermistors Breakout cables required for conducted emissions testing LAT-DS-06531 LSC to RF shield, SIU power LAT-DS-06530 BPU PNL to LSC, SIU power LAT-DS-06528 BPU PNL to LSC, LSC to DAQ, DAQ power

Test Software: 

Test Software Emissions Testing – Script # LAT-171 LAT configured to collect muons with additional periodic trigger to appropriately populate the T&DF data flow and science data stream to the VSC. Susceptibility Testing – Script # LAT-181: LAT configured to collect muons with CAL triggers (flight level) and ACD vetos enabled. Susceptibility monitoring TKR event occupancy CAL pedestal widths (noise) and trigger rates ACD pedestal widths (noise) and veto rates T&DF commanding and data flow errors Real time monitoring Strip chart of most susceptible TKR tower/tray occupancies Strip chart of CAL / ACD trigger rates Strip chart of LAT trigger rate and deadtime Diagnostic error messages Post processing Global TKR occupancy vs time Global CAL, ACD pedestal widths vs time


Personnel EMI/EMC Test Director - Michael Lovellette EMI/EMC Facility Operations Mike Obara - Test Conductor Tony Grey - Test Conductor LAT Instrument Operations Brian Grist – Operations Lead Standard LAT I&T Operators and Online analysis support

EMI/EMC Test Summary: 

EMI/EMC Test Summary Ready to test Facility ready to support test No outstanding issues with subsystem testing except completion of radiator VCHP heater CS / RE verification Supporting analyses for static magnetic field have been accepted by Blanchette for GLAST project Supporting analysis for RS103 18 – 40 GHz performance is in progress. Need closure of ACD contribution to the analysis with Blanchette.

RE102 - Integrated LAT: 

RE102 - Integrated LAT

RE101 – All LAT Equipment: 

RE101 – All LAT Equipment

CE102 Spacecraft PRU – LAT DAQ: 

CE102 Spacecraft PRU – LAT DAQ

CE102 Spacecraft PRU – LAT SIU, VCHP Htrs: 

CE102 Spacecraft PRU – LAT SIU, VCHP Htrs

Conducted Emissions Common Mode: 

Conducted Emissions Common Mode

RS103 Perform – LAT: 

RS103 Perform – LAT

RS101 Perform – LAT: 

RS101 Perform – LAT

CS102 Spacecraft PRU – LAT DAQ: 

CS102 Spacecraft PRU – LAT DAQ

CS102 Spacecraft PRU – LAT SIU, VCHP Htrs: 

CS102 Spacecraft PRU – LAT SIU, VCHP Htrs

Conducted Susceptibility Common Mode : 

Conducted Susceptibility Common Mode

CS06 Operate – All LAT Equipment: 

CS06 Operate – All LAT Equipment

CS06 Perform – All LAT Equipment: 

CS06 Perform – All LAT Equipment

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