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GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Persis S. Drell

Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Persis S. Drell Stanford Linear Accelerator Center LAT Deputy Project Manager persis@slac.standford.edu 650-926-8791. Outline. Technical Status- last month’s accomplishments

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GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Persis S. Drell

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  1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Persis S. Drell Stanford Linear Accelerator Center LAT Deputy Project Manager persis@slac.standford.edu 650-926-8791

  2. Outline • Technical Status- last month’s accomplishments • Issues identified and closure plans • Status of flight hardware • Cost and Schedule Status • Tower A Schedule • Delivery schedule for Tower B—Tower 16

  3. Accomplishments and Issues Identified in Tower A Fabrication • Tracker Tray Fabrication • Bias circuit bonding problem resolved • MRB 10/1/04 • Flight tray production restarted 10/4/04 • Tray Production Status (Plyform + INFN) • >90 bare trays (no converter or bias circuits) produced • Converter production • Tiles for Tower A at Plyform etched in Turin, primed in Plyform • Tiles for Tower B and beyond being etched and primed at GSFC • Delivery rate plan of 300 tiles/week • 21 trays completed with converter and bias circuit through T/V • 1 failure • 2 tiles had primer delaminate from converter foils (Turin process) • Cause under investigation • 3 others show bubbles (before T/V) • Disposition under discussion

  4. FLIGHT TRAYS SUMMARY Production Step Qty-FH Bare Panel 73 ESPI done 56 Panel with payload 20 T-VAC done 10 Tray Production Status (example)

  5. Issues Identified in Tower A Fabrication • Tower A Tray Assembly Status (G&A) • Anomaly found in assembly: missing connections on MCM • WORK IS STOPPED • 1 tray with MCMs bonded (but no SSDs yet) found to have a problem with no bias from the MCM to the two center ladder attachment points on the bias circuit. • One caused by resistor badly soldered on MCM • Cause of other is not yet known • 6 more MCMs of 32 tested in Pisa have at least 1 missing bias or HV connection • 18+ tested at SLAC do not show any problem • Currently applying all available resources in Pisa and at SLAC to determine root cause • G&A work is ~ 1 week behind nominal Tower A fabrication schedule at this point

  6. MCM and Bias Circuit

  7. Issues Identified in Tower A Fabrication • Other Issues for Tower A • In Tower 0, identified interference between connector on MCM and sidewall on many trays • New MCM bonding procedures finalized to ensure connector stay clear • Critical hardware for Tower A assembly in work • Impacted by SLAC shutdown • Pulled work from shops and sent outside to complete • Flight cables for Tower A a critical problem

  8. Issues Identified in Flight Cable Production • Two technical issues identified: • Separations between barrel plating and internal layers. • Bubbles in adhesive holding connector to cable

  9. Path forward with Tracker Flex Cables • Parlex • CAP developed for plating process • Early tests validated new process • Coupon tests on cables with new plating process so far test acceptable • Process problems in cable assembly under discussion • Bubbles in the adhesive between the flex and the Omnetics connectors. • Stop work issued—QA visit tomorrow supported by tracker personnel • Delivery schedule continues to be unreliable • Project Manager to visit next week • Option: If new process has good coupons, consider getting bare cables and assemble at company of our choosing • Investigations underway • Current proposal to install cables in hand (with original plating process or with adhesive bubbles) if necessary to stay on schedule for Tower A assembly • Tower A will have lien to be resolved at a later time

  10. Alternate sources for tracker flex cables • Developing alternate source for full length cables • PO at Titan with 12/1 delivery to produce 5 C4 cables • Will proceed with QA source inspection if looks viable • Developing option of 2 short cables with ‘rigid-flex’ joint • Need to validate design • New drawings in process • Anticipate flight order with alternate source by 12/15

  11. Alternate sources for tracker flex cables

  12. Issues Identified in MCM Production • 343 units delivered to SLAC • 325 through burn in and final test at SLAC • Need 686 for 18 towers + electronics group • Production at Teledyne currently stopped • MCM Issues • Pitch adaptor • 13.5% drop out at MIP 1 due to broken traces (visual inspection) • Brittle Ni plating cracks easily in bend region, sometimes also cracking Cu • Two new pitch adaptor concepts in work to eliminate problem • Option 1: masking over bend radius • Option 2: selective plating process for Ni plating • New designs to be qualified when production at Teledyne resumes (scheduled for 11/15) • New electrical test fixture in test for detecting broken traces

  13. Issues Identified in MCM Production • MCM Issues (cont.) • MCM Leakage Current Problem • 8 boards have developed low resistance between layers 7 and 8 (120 V potential difference) of the multilayer board during burn-in. • Destructive Physical Analysis in process at Goddard and CALCE to determine root cause • Moisture during lamination or reflow, contamination, and conductive filament growth are all possibilities. • In case it is moisture, a pre-reflow bake has been added. Prepreg will be vacuum dried if more PWBs are made. • The problems seem clustered, so we are holding PWBs from the same panels as failed boards • The MCMs failed 2, 3.5, 4, 6, 10, 20, and 75 hours into our 168 hour burn-in where about 350 others did not fail giving hope that the burn-in catches almost all the problems. • Data readback errors • Some MCMs are too sensitive to clock duty factor during burn-in • Related to quality of clock received by GTRC • Problem mitigated by changing termination resistor on cables

  14. Issues Identified in MCM Production • MCM Conformal Coating Problems • Issues identified in QA with peeling, contamination and bubbles • A full inspection of all units has been completed. • CC got into many connectors. • They will be carefully cleaned • CC is lifting in small areas near components. • 200 thermal cycles did not make the lifting worse. • 3 vacuum cycles on 4 MCMs did not make lifting worse • The risk involved in reworking them may be greater than in using them as is. • CC is thin or missing on sides of many components • Due to spraying from only one direction • Mostly on non-conductive sides of “tall” components • Not clear if rework is practical. (CC could end up too thick.) • MRB 10AM 11/3/04 • In parallel, manufacturing process is being improved to prevent these problems on future units.

  15. Issues Identified in MCM Production • Restart of MCM Flight Production • Need improved ESD and PWB bake-out • Waiting for final quote • Implement conformal coat process improvments • Pitch adapter re-qualification program • MC restart MRR at Teledyne anticipated 11/15/04

  16. Flight Hardware Drawings Status • Top/Bottom Tray Panels (including flexures) • All drawings complete and released. • Interface Hardware • All complete and released. • Mid Tray Panels • Some rework and improvements of the drawings to reflect as-built condition are in work. • Tray Assembly (Bonding MCMs + Ladders to tray panels) • All complete and released. • Sidewall Drawings • All complete and released. • Heat Straps • Complete and released.

  17. Flight Hardware Drawings Status • Flex-Circuit Cables • All complete and released. Drawing revision to match as built in progress • Top Mount Cable Retainer and Alignment Hardware • All complete and released. • Tower Assembly Drawing • Complete and in release cycle • Electronics, including SSDs, MCMs, Bias Circuits, ASICs, etc.: all complete and released. • Ladder drawing revised to match as built. • Ready for release

  18. Status of Parts & Materials from SLAC

  19. Status of Parts & Materials from SLAC

  20. Status of Parts & Materials from SLAC

  21. Status of GSE from SLAC

  22. Status of GSE from SLAC

  23. Status of GSE from SLAC

  24. PMCS Schedule & Cost Variance • September: Schedule variance decreased from -$736k to -$575k on total $15,274 BCWI • Schedule has actually degraded due to work stoppage at Teledyne • Improvement in PMCS comes from receiving prepreg used for sidewalls • Keep in mind most of Tracker assembly work is in Italy and not tracked by this schedule variance calculation • Cumulative Cost Variance: -$456k • Large payment made to Teledyne for MCM’s received before work stoppage

  25. Schedule Status: Tower A Campaign • The Tracker team is focused on delivery of Tower A to I&T • Updated plan: Tower A ships 12/16/04

  26. Schedule Status: Tower Delivery Schedule • Updated plan: • Start production 10/4 • Plyform produces 4 trays/day starting 11/1 • G&A going to 2 shifts • Extra CMM • Extra Wire bonder • Tower 13,14 arrive in May

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