Electrical

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Section 16 Electrical
. . . Bruce Zink EO-1 Electrical Lead, Swales
Aerospace, Inc.
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Contents

• System Block Diagram
• Verification Matrix
• Failure Free Time
• Changes since last review
• Remaining Work to be Performed
• Critical RFAs
• Status of Open Actions
• Residual Risk
• Launch Readiness

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System Block Diagram
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Power System Block Diagram
5
As Run Verification Matrix
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Projected Power On Time
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Changes Since Red Team Review

• WARP re-integration
• Following WARP repair and test
• Calorimeter integration and verification
• ACDS removal, rework, and re-integration
• Interpoint converter stiffener installation
• GPS Power Converter Unit removal, rework, and
  re-integration
• Interpoint converter stiffener installation
• AST removal, rework, and re-integration
• Interpoint converter stiffener installation

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Changes Since Red Team Review (continued)

• IRU re-integration
• Following removal to prevent Helium exposure
• 1773 Bus Characterization
• Verify bus performance following breaking
  connections to ACDS, WARP, Hyperion, and AST
• Minimum system margin gt9dB over temperature range
• Trickle Charge Diode Installation
• Replaced fuse with diode and tested successfully
• S-Band Transponder Removal
• Returned to manufacturer due to AGC oscillations
• Integrated command uplink bypass to continue
  powered testing

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Remaining Work To Be Completed

• Harness Closeouts
• Remaining work related to re-installation of
  S-Band transponder and bay closeouts for flight.
• S-Band Transponder Repair
• S-Band Transponder Re-Integration
• Repeat of previous successful integration
  following repair
• Hyperion Re-Integration
• Repeat of previous successful integration
  following removal to allow integration of S-Band
  Transponder

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Remaining Work To Be Completed (continued)

• S/A Integration
• Repeat of previous successful integration for
  Vibration Acoustic Test
• 1773 Bus Characterization (following Hyperion
  final integration)
• Required due to Hyperion de-mate
• Repeat of previous successful integrations
• Performed 7 times to date

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Status of Open Actions

• 1773 Bus Fault During MOC Sim (WOA 876 PR20-1,
  20-3)
• Modification of PSE default power on
  configuration mitigated problem
• PSE SW Build 8.1 performs load shed of all
  non-essential loads following special command
  reset
• Solar Array Deployment Test
• All testing to date successful
• Planned for launch site
• Primary side with flight fuse plug

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Residual RiskOne Time Events (Redbook Items)

• Chassis current Transient (WOA 770-20-3,
  PR20-3)
• One event of 300mA, also seen on stripchart
  recorder
• EMC testing was taking place with probes
  connected to spacecraft power bus
• No recurrence since event on 11/22/99
• 1390 Hours of powered testing
• Chassis current event (WOA 572-30-10)
• Prolonged chassis current event reaching a peak
  of 925 mA
• Ad Hoc testing immediately following event caused
  brief recurrence of anomaly
• Solar Array Simulator cable (EGSE) found to have
  split insulation on multiple wires within
  backshell
• Following inspection a new Solar Array Simulator
  cable was fabricated
• No recurrence since 8/20/99 ( with exception of
  770-20-3 which was a brief event )
• 2370 Hours of powered testing

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Residual Risk(continued)

• 1773 Bus Fault during MOC Sim (WOA 876-20-1 and
  876-20-3, PR20-1, 20-3)
• 1773 bus susceptible to babbling transmitter
• Low risk of fault (TRMM and XTE heritage)
• Change in PSE default services mitigated risk
  associated with this problem (Version 8.1)
• Special command reset sheds all non-essential
  loads
• Operational ability to re-set or power down all
  non-essential RTs
• Ability to remove babbling RT, or re-set and stop
  babbling
• Low likelihood of occurrence combined with
  operational workarounds results in low risk
  associated with this issue
• S-Band Transponder Anomaly
• AGC oscillations must be diagnosed and repaired
• See Special Topic

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Launch Readiness

• Complete troubleshooting of S-Band Transponder
• Locate problem
• Fix problem
• Integrate and Test S-Band Transponder
• Repaired unit
• Complete system level testing (CPT, S/A
  deployment)
• Previous success suggests low risk
• Complete remaining activities
• See previous section on Remaining Work to be
  Completed
• Low risk S/C closeouts and repeats of previous
  integrations
• Ready for launch following previously mentioned
  activities

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Special Topic Follow-Up Nadir Deck Heater Short
. . . Bruce Zink EO-1 Electrical Lead, Swales
Aerospace, Inc.
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Nadir Deck Short Circuit

• Summary of Event (WOA 676-20-8)
• Mis-wired heaters caused high current events in
  first TVAC
• Repair Implementation
• Heater circuits and switched services in question
  abandoned
• New heaters installed on nadir deck
• Re-wiring performed to re-establish lost services
• Test and Verification
• Circuits tested by jumpering thermostats
• Circuits verified in T/V II cold plateau
• Negligible residual risk

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Special Topic Umbilical Console Operational
Issues
. . . Bruce Zink EO-1 Electrical Lead, Swales
Aerospace, Inc.
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Description of Problem

• GPIB bus internal to Umbilical Console suffers
  from periodic crashes
• Conflict on bus (cause not fully understood)
  results in loss of commanding and status
  telemetry from solar array simulators and Direct
  Power Converter supply
• Existing configuration of supplies remains
  following a crash
• Commanding of output relays for the solar array
  simulators and DPC is not affected by GPIB
  crash
• Communications with ASIST is not affected by a
  crash
• Does this situation create risk associated with
  Launch??

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Umbilical Console Block Diagram
Ethernet ASIST Link
Switch Control
Windows NT Computer

• ASIST used to command UC and acquire telemetry
• GPIB Bus used to control settings on power
  supplies
• Sorenson Bus mimics GPIB bus for remaining
  supplies
• Output relays controlled via dedicated hardware
  not on GPIB bus

HP Solar Array Simulator
GPIB Bus
To Spacecraft
Sorenson DPC/Master
Sorenson SAS 3
Sorenson Bus
Sorenson SAS 10
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Umbilical Command Timeline

• Power up
• Configure DPC to 30V
• Close DPC output relay
• Bring S/C Battery On-Line
• Adjust DPC to match battery voltage
• Send battery on pulse
• Open DPC output relay
• Adjust DPC voltage to 22VDC
• Configure Solar Array Simulators
• Adjust HP SAS and all Sorenson supplies to
  standard settings

Denotes use of GPIB Bus
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Umbilical Command Timeline

• Standard Spacecraft Operations
• Cycle SAS output relays to control battery
  charging
• Launch (T-5 minutes)
• Open all SAS output relays to go to internal
  power
• Scrub/Power Down Spacecraft
• Adjust DPC to match battery voltage (iterative
  process)
• Close DPC output relay
• Issue battery off pulse
• Open DPC output relay

Denotes use of GPIB Bus
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Umbilical Recovery Procedure

• Wait for spacecraft night
• SAS supplies reconfigured during recovery, no
  effect on spacecraft when SAS output relays are
  open
• Exit Umbilical SW program
• Performed using remote administration from
  remotely located computer
• Cycle AC power to Sorenson DPC supply
• Performed using remote controlled power switch
• Controlled via fiber link from remote PC
• Re-start Umbilical SW program
• Performed using remote administration from
  remotely located computer
• Continue testing

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Summary

• Problem has seen extensive effort by a large
  group of people
• Definitely related to Sorenson internal bus
• Unable to precisely locate and fix problem
• Further attempts to fix problem are
  counter-productive
• Configuration changes this close to launch carry
  risk of other problems
• Recovery procedure is in place, and exercised
  regularly
• Problem cannot threaten launch
• See command timeline, which shows no GPIB
  activity required to handle launch (following
  initial configuration)
• Power up and SAS configuration completed gt8 hours
  prior to launch
• Recovery time is on the order of 10 minutes
• UC crash occurred during last Launch Sim, S/C
  launched successfully and on time!!!

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Special Topic Solar Array Cable Damage PR
1045-40-1
. . . Bruce Zink EO-1 Electrical Lead, Swales
Aerospace, Inc.
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Solar Array Cable Damage

• Background
• During final panel closeout inspections on June 6
  a hair line mark (centered around three o'clock)
  was noticed on the 86 wire bundle that comes out
  of the SADA
• The hair line mark was further inspected and
  determined to be a cut of the insulation for
  seven wires. The geometry of the cut indicated
  damage due to a sharp object. It must be noted
  that this cut was very difficult to see due to
  fine cut. The location of the cut is
  approximately 0.75 inches off the face of the
  SADA interface which is approximately at the
  start of the bend radius for the cable bundle as
  it is folded up against the Solar Array Yoke.
  This obviously is a high stress area.
• Under higher magnification (10 - 20x) it was
  determined that at least three wires had exposed
  copper. In addition oxidation has occurred
  indicating the damage was done some time ago.

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Solar Array Cable Damage

• Background (continued)
• All seven wires were verified as follows
• Connector Pin Description - Function
• Cable Wrap J2 7 Inboard S/A panel structural
  ground
• Cable Wrap J2 37 Circuit 11 (outboard panel
  fixed string)
• Cable Wrap J2 19 Circuit 4- (Outboard panel,
  shuntable)
• Cable Wrap J2 38 Guard (ground wire shield for
  CSS)
• Cable Wrap J2 14 Guard
• Cable Wrap J2 42 Guard
• Cable Wrap J2 27 Coarse Sun Sensor 2

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Solar Array Cable Damage
Detail View A
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Solar Array Cable DamageClose-up
Detail View A
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Solar Array Cable Damage

• Probable Cause
• It is believed that this damage occurred while in
  the 238 TV chamber in the preparation of the
  Spacecraft for TV (October 99) or while clearing
  out the GSE blankets in and around the SADA .
  This can not be verified and it is more than
  likely an accident which went unnoticed. The
  SADA and cable wrap were thoroughly inspected via
  bore scope shortly before TV and was found to be
  nominal.
• Prior to TV 1, a through inspection was
  performed in this area without issue
• No work has been done in this area since leaving
  TV, until recently
• Cutting instruments are generally used in chamber
  operations (TC number cutting, GSE MLI
  clearing,etc.)
• One TV GSE cabling was found damaged in similar
  manner following TV
• Configuration in chamber was not conducive to
  ideal working conditions for technicians due
  to extremely tight configuration and poor
  lighting
• QA oversight was from distance during T/V buildup
  and T/V teardown in chamber due to continuous
  monitoring of Oxygen level at chamber door due to
  concern of nitrogen Purge in closed chamber.
  Safety of personnel was first priority! Also
  there was insufficient room to have two people in
  the same physical area.
• Other post TV activity require use of razor
  blades (Radiator tape cutting, excess adhesive
  removal/trimming, etc.) however this has been
  limited and is under constant monitoring by QA

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Solar Array Cable Damage

• Corrective Action
• Based on the type of damage critical location
  it was determined by both Swales Aerospace GSFC
  Quality (M. Kelly) that this damage could not be
  repaired by splicing or any other means. The
  wires associated with pin J2-7, J2-37, J2-19,
  J2-27 would need to be replaced by swapping with
  existing spares within assembly.
• Implementation of swap was made using a patch
  cable due to access restrictions.
• Make use of current internal Bay 5 SADA cabling
  interface connection
• Fabricated Connector Bracket Assembly which
  essentially swaps wires (J2-7, J2-37, J2-19
  J2-27) with the spares

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Bay 4 View of SADA
Detail View B
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Bay 4 View of SADA
Detail View B
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Solar Array Cable Damage

• Corrective Action (continued)
• In addition to the fabrication of Connector
  Bracket Assembly the following other actions
  were taken
• Millohm insulation resistance (cross pin)
  testing of entire cable to verify all wires prior
  to initiating of change rework of damaged
  cables
• Although J 2-7, J2-37, J2-19, J2-27 wires were
  abandoned, exposed copper insulation wiring was
  covered. Guard wires were also reworked.
• Millohm HiPot entire cable following rework.
  (Connector Bracket Assembly testing which also
  includes HiPot testing performed prior to
  delivery to Spacecraft)
• Integrated Connector Bracket Assembly with Cable
  Wrap Assembly
• Verified all SADA signals with Connector Bracket
  Assembly installed
• Followed by full SADA functional
• Following completion of S/C bay closure a S/C
  Aliveness Test was performed

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Solar Array Cable Damage

• Corrective Action (continued)
• Other Global actions taken
• Inspected all external cabling prior to blanket
  installation.
• Fabricated Red Tag Item to cover critical area of
  Solar Array cable. It will be removed prior to
  Solar Array installation.
• Rework of cable harness will have no effect to
  overall deployment of Solar Array
• Deployment Hinge has gt4x Torque margin for worst
  case environmental effects

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Connector Bracket Assembly Fitcheck on
SpacecraftMonday 6/12/00 - 1400
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Summary

• All repairs and preventative measures implemented
  successfully
• All changes documented in appropriate drawings
• Extensive spacecraft testing has taken place
  since repair, including a full TVAC test with no
  anomalies related to the cable wrap assembly
• Negligible residual risk
• Ready to fly