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GLAST Large Area Telescope LAT Pre-Shipment Review EMI/EMC Michael Lovellette, Test Director Naval Research Lab PowerPoint Presentation
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Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope LAT Pre-Shipment Review EMI/EMC Michael Lovellette, Test Director Naval Research Lab. EMI/EMC The Bottom Line . No emissions excesses found in any LAT system level test, CE or RE One susceptibility found

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Presentation Transcript
slide1

Gamma-ray Large Area Space Telescope

GLAST Large Area Telescope

LAT Pre-Shipment Review

EMI/EMC

Michael Lovellette, Test Director

Naval Research Lab

EMI/EMC

slide2

EMI/EMC The Bottom Line

  • No emissions excesses found in any LAT system level test, CE or RE
  • One susceptibility found
    • Tracker occupancy specification of <10-4 violated at ~100 MHz vertical polarization in RS
      • Nothing on the vehicle radiates in this frequency band
      • Also unlikely for external radiation
      • Not considered a problem, waiver submitted
  • EMI report in preparation, LAT-TD08585-01

EMI/EMC

slide3

Purpose / Contents

  • Demonstrate LAT complies with all EMI/EMC requirements:
    • Conducted and radiated emissions below required levels
    • LAT does not exhibit susceptibilities when exposed to conducted or radiated energy at required levels
  • Test Categories
    • Conducted emissions (CE)
    • Radiated emissions (RE)
    • Conducted susceptibility (CS)
    • Radiated susceptibility (RS)
  • Requirements flowdown
    • Mission System Spec  433-SPEC-0005
    • LAT Environmental Requirements Spec  LAT-SS-00778
    • LAT Performance Verification Plan  LAT-MD-00408-04c
    • EMI Test Plan  LAT-MD-02726-02

EMI/EMC

radiator subsystem emi emc test
Radiator Subsystem EMI/EMC Test
  • 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 was performed just prior to LAT RE102 test.
  • Not formally part of the LAT level EMI test, performed on an STR

EMI/EMC

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 & CEDM* 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

* Not required but we did it anyway

EMI/EMC

lat power interfaces
LAT Power Interfaces
  • SC-LAT Power Interfaces
    • SC PRU (P) - LAT DAQ
    • SC PRU (R) - LAT DAQ
    • 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 PDU (P) - LAT Makeup Heaters (Survival)
    • SC PDU (R) - LAT Makeup Heaters (Survival)

Makeup circuit power interfaces are not tested.

VCHP heater testing limited to RE102

EMI/EMC

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
  • Redundant side testing limited to Conducted Emissions (CE102) and Conducted Susceptibility (CS102)

EMI/EMC

as run test sequence
As Run Test Sequence
  • 22 June
    • CSCM DAQ primary bus
    • CSCM SIU primary bus
    • CS06 DAQ primary bus
    • CS06 SIU primary bus
    • CS102 DAQ primary bus
    • CS102 SIU primary bus
  • 23 June
    • CS06 SIU primary bus
    • CS102 DAQ primary bus
    • CS102 SIU primary bus
  • 24 June
    • CS102 DAQ redundant bus
    • CE102 DAQ primary bus
    • CE102 SIU primary bus
    • CECM SIU primary bus
    • CEDM SIU primary bus
    • CS06 retest
    • CECM DAQ primary bus
    • RS101 retest
  • 10 July - High Bay
    • CS102 retest DAQ & SIU primary bus
  • 12 June - High Bay
    • CE102 DAQ hot & ret redundant bus
    • CE102 SIU hot & ret redundant bus
  • 13 June
    • CS 102 DAQ ret redundant bus
    • CS102 SIU hot & ret redundant bus
  • 15 June - Anechoic Chamber
    • RE 102 calibration
    • RE102 Test
  • 16 June
    • RE102 continued
  • 17 June
    • RS103
  • 19 June
    • RS103 continued
  • 20 June
    • RS103
    • RE101
    • RS103 retest
  • 21 June
    • RS103 retest
    • RS101

EMI/EMC

deviations from emi test plan
Deviations from EMI Test Plan
  • UHF Notch shown in Figure 36 not included in RE102 requirement
    • Table 6 Gives correct notches
  • CS102 pulse level 10 V as indicated in text, not 20V as shown in Figures 27 and 30.
  • CEDM test not required
    • We did it anyway
  • During initial RE testing some radiator connectors not connected
    • No change noted once they were connected
  • During redundant side CS test 150kHz to 10MHz signal injection was lead was inadvertently connected to a thermistor lead
    • Incorrect lead stripped for access
    • Thermistor passed CS testing with flying colors
    • Test successfully repeated during primary side CS testing using correct pin number

EMI/EMC

deviations from emi test plan cs102

Chamber

Bulkhead

RF Generator

Attenuator

RF

Amp

Spectrum

Analyzer

≥100 H

(if necessary)

Attenuator

LAT-SIU Interface

VSC

LSC

(+)

≤ 5 cm

(-)

In

Out

Deviations from EMI Test Plan - CS102
  • Impossible to locate current probe between injection point and LAT connector due to the twisted pair type wiring
  • Current probe was located at LSC
    • Reduced current feedback sensitivity
  • Pre calibrated current limits used

EMI/EMC

lat grounding
LAT Grounding
  • Before Radiated Testing the LAT was positioned on copper sheets and all grounds were connected with 18” Cu sheets

EMI/EMC

radiator emi test
Radiator EMI Test
  • The radiator was connected to the special power supply
  • The first run showed power supply harmonics over the limit

EMI/EMC

conducted emissions
Conducted Emissions
  • All conducted emissions tests passed comfortably
    • Representative plot shown here.

EMI/EMC

conducted susceptibility
Conducted Susceptibility
  • The only susceptibilities detected during conducted testing were additional noise on RTD temperature measurements
    • This imposed ± 2 or 3 degrees noise on the temperature readout
    • Some of the readouts affected were VCHP reservoir temperatures used by the thermal control software
    • Does not violate any requirements, but worth noting for thermal control software design
  • This additional noise can be accommodated by a modification to the digital filter in the thermal control system
    • D. Wood has modified filter and tested against noise data taken during EMI CS test

EMI/EMC

cecm cscm cs06
CECM, CSCM, CS06
  • All LAT system tests nominal
  • There was an exceedence during subsystem CECM test on the heater control box (HCB) VCHP reservoir heater feed.
    • No retest performed at system level
    • Waiver approved by project office, CCR 433-0374

EMI/EMC

radiated emissions
Radiated Emissions
  • All radiated emissions, RE101 & RE102, were below required levels
  • All broad band was well below the limit
  • SGLS notch also passed easily
  • GPS notch required some additional shielding of test harnesses, connectors and connector savers to get below limits

EMI/EMC

radiated susceptibility rs103
Radiated Susceptibility - RS103
  • RS103 Test sweeps were performed and data analysis performed off line
  • ACD, CAL and TKR performance verified

EMI/EMC

radiated susceptibility rs101
Radiated Susceptibility - RS101
  • RS101 tested limited locations
  • Connectors
  • Tracker

EMI/EMC

radiated susceptibilities
Radiated Susceptibilities
  • LAT exhibited increased tracker occupancy at ~33, 66, & 99 MHz during testing with vertical polarization
    • Effect noted during post test processing
    • Only the 99 MHz frequency violated tracker occupancy requirement of < 10-4
  • There are no sources of EM radiation on the S/V at these frequencies and the frequency is below most external sources
  • Considered not to be a problem
  • Waiver submitted to project office

EMI/EMC

personnel
Personnel
  • EMI/EMC Test Director - Michael Lovellette
  • EMI/EMC Facility Operations
    • Mike Obara - Test Conductor
    • Tony Gray - Test Conductor
  • LAT Instrument Operations
    • Brian Grist – Operations Lead
    • Standard LAT I&T Operators and Online analysis support
    • Anders Borgland – Offline instrument analysis lead
    • Elliott Bloom – LAT181 analysis lead

EMI/EMC