Transcript ppt
GLAST LAT Project Gamma-ray Large Area Space Telescope F2F, June 15, 2005 GLAST Large Area Telescope: Performance & Safety Assurance Joseph Cullinan SLAC Performance & Safety Assurance Manager [email protected] (650) 926-5034 F2F – June 15, 2005 GLAST LAT Project Status and Issues • DAQ - Transition of QE personnel to support electronics hardware testing has been effective to support inspection, data review, documentation review/management and NCR documentation of TEM/TPS and PDU testing - TEM/TPS environmental testing running smoothly - No NCRs on last T/V test of two TEM/TPS assys - Supporting cCPI connector solder attach process development at Aeroflex for backplane and plug-in boards (GSFC performing test board evaluation) - Trying to resolve problems with incomplete solder fill around some connector leads soldered through boards F2F – June 15, 2005 GLAST LAT Project Status and Issues • Cables Recent MRB with GSFC involved two cable issues: - Three PDU cables reworked in-house did not repeat full electrical acceptance testing per NASA cable assy standard prior to shipment to Aeroflex - Cables were returned to vendor to complete testing and have been returned to Aeroflex for PDU assembly and meet NASA standards - All cables reworked at vendor are fully retested, so this issue was isolated to cables reworked in-house. - Cables with metallic braid shielding do not include a kapton tape wrap around the wires to provide additional layer of protection between wires and external braid - Practice is recommended by NASA standard but not required - Big risk is cold flow of teflon wire insulation under stress caused by over-tightening of tie wraps or bending cables over sharp edges or tight radii (less than 3x cable diameter) - Evaluation of cable tray layout shows no expected bending over sharp edges or tight radii. Tie wrap installation and compression will be controlled with approved and calibrated installation tool. - Plan is for no change to cable design (expected 6 week delay in remaining cable delivery schedule to add extra insulation layer) F2F – June 15, 2005 GLAST LAT Project Status and Issues • Flex Cables (Pioneer Circuits, Inc) Supported start up of panel production at Pioneer (second source) - Final drawing changes, documentation review, clarification of requirements (MIPs, test coupon evaluation requirements, annular ring requirements) - Supporting development of Omnetics connector epoxy attachment process, including test coupon fabrication, inspection for connector cracking, shear testing • Flex cables (Parlex) Omnetics connector cracking in insulation between sockets is still an issue. Cracks are observed (30x magnification) after epoxy bonding connectors to cables; only very few as-received connectors were found to have cracks Parlex evaluating bonding process that uses no compressive load on connectors. Initial test samples showed shear strength equivalent to connectors bonded with compressive load. This may reduce/eliminate cracks observed in connectors following attachment to cables. MRB with GSFC scheduled for tomorrow to review data to date and determine acceptance criteria for cables that have cracks (current acceptance criteria is no cracks) - This includes review of voltage breakdown analysis and current leakage testing of cracked connectors that indicate existence of cracks may have little effect on electrical performance of connector - Removing and replacing bonded connectors is difficult and damage during rework process can result in loss of entire cable F2F – June 15, 2005 GLAST LAT Project Status and Issues • Teledyne - Continued support of final TMCM production Latest issues: Cutting tool used to trim pitch adapter after attachment to board malfunctioned two weeks ago and several boards were scrapped following trimming. LAT QA performed inspection of test and flight boards trimmed with refurbished tool to requalifiy tool for production; so far no issues with tool. Teledyne appears to be giving up on outside vendor (Plasma Systems) to conformal coat TMCMs because of ongoing quality issues. Teledyne has continued to coat boards inhouse. • Lockheed Martin - Supporting X-LAT and radiator panel testing - Held MRB May 13 to review X-LAT heat pipe thermal bond void issue. Plan to schedule follow-up MRB with LM and GSFC to review infrared imaging of voids before and after XLAT testing to determine final disposition.