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GLAST Large Area Telescope: Face to Face Meeting March 17, 2005

GLAST Large Area Telescope: Face to Face Meeting March 17, 2005 AntiCoincidence Detector (ACD) Subsystem WBS: 4.1.6 David J. Thompson Thomas E. Johnson NASA Goddard Space Flight Center Subsystem Manager/Instrument Manager David.J.Thompson@nasa.gov Thomas.E.Johnson@nasa.gov.

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GLAST Large Area Telescope: Face to Face Meeting March 17, 2005

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  1. GLAST Large Area Telescope: Face to Face Meeting March 17, 2005 AntiCoincidence Detector (ACD) Subsystem WBS: 4.1.6 David J. Thompson Thomas E. Johnson NASA Goddard Space Flight Center Subsystem Manager/Instrument Manager David.J.Thompson@nasa.gov Thomas.E.Johnson@nasa.gov

  2. Significant Accomplishments • All flight phototubes are complete. • Flight Electronic Chassis 4R installed on ACD. • Completed vibration and TVAC testing of Flight Electronics Chassis 2L, 1L, and 3L. 2L is ready for integration to ACD. • Upgraded to LATTE 4.7.3. Enlisted help for test software development.

  3. Electronics Chassis Assembly and Test Plan 8X Base Electronics Assembly (1) Electronics Chassis (8) (4 double + 4 single)

  4. Schedule Flow 10/4 – 2/5/05 2/7 - 2/15 Qual Electronics Chassis Environmental Test 1st flight chassis Environmental Acceptance Test (8d) The remaining Seven Flight Chassis Environmental Acceptance tests (25d) 2/16-3/23 6/10/04 – 1/28/05 2/28 – 3/18 2/15 – 2/22 Assemble last 2 rows of TDAs & WSF (124-130, 224-230, 324-330, 424-430) onto TSA Initial TDA/TSA I&T in B7 Install & test 1st flight Chassis onto ACD Install & test remaining flight Chassis onto ACD 4/12 (TBR) 3/24 – 3/30 4/14 – 4/19 descoped 4/11 – 4/12 3/31 – 4/9 3/23/05 Vibration Test (5d) EMI/EMC Test (9d) Pre- Environmental Review (PER) Install Thermal Blanket & MMS(4d) ACD Subsystem Efficiency Verification test (include rotate ACD 90 degree)(10d) ACD Full Functional Test(6d) ACD Integration complete 5/24 – 5/28 4/20 – 4/22 4/23 – 5/12 5/13 – 5/14 5/17 5/18 – 5/23 5/28 Acoustic Test (3d) Thermal Balance/ Thermal-Vac Test (20cd) Mass Properties (2d) Pre-ship Review (PSR) ACD ship to SLAC (5d) Post ship Check out (5d) ACD RFI

  5. Issues and Concerns • The principal issue is schedule, which drives cost. • Anything that affects our extremely aggressive schedule is a concern. • Snow • EGSE • EMI • Magnetic Shields • Additional vibration testing • Documentation (CMMI, test reports, data packages etc..)

  6. EGSE – Test Stands Recent Activities • Crashes in long runs traced to memory leaks, mostly in third-party software. Fixed as of LATTE 4.7.3. • We have modified ACD software to handle the new features and are running LATTE 4.7.3. ACD software development has been more time-consuming than expected (ACD issues, not related to LATTE 4.7.3). Unfinished Work: 31 scripts needed. 28 working, 3 in development. • The unfinished scripts are those needed to test detectors and full ACD. • Software for handling calibration files and establishing baselines is still in development (not just scripts) Some help from the GLAST Project and the Calorimeter • GLAST Project has extended funding for our lead software developer, who was scheduled to move off ACD due to funding limitation. • GLAST Project funded a short-term test conductor, freeing up time for our other test conductors to concentrate on script and calibration file development • Byron Leas of the Calorimeter group has agreed to help with software to handle calibration files. Thanks, Neil and Byron!

  7. EMI – Waivers and Additional Tests • The ACD qualification chassis did not meet all the EMI/EMC requirements. Emissions are higher at some frequencies than the LAT specification, including one in the GPS band. There are no simple fixes. GLAST Project may request a re-test. • CSCM test, which was skipped at recommendation of Goddard EMI personnel, has been replaced with CS114 test (a safer version of the same test). This test can be run in the lab. • The principal ACD descope is to eliminate EMI testing at the full ACD level, which requires a waiver of this test requirement. The basic rationale is that we do not have a flight interface and would have to do testing with our unshielded GASU under the ACD (for cable lengths), making any test results suspect. • CR has been submitted to the LAT. No action yet. Rebaseline savings of cost and schedule have assumed this CR is approved.

  8. Magnetic Shielding Phototube Cap Magnetic Shield. ACD tried to save some money by using a combination of stainless steel (154 locations) and mu-metal (40 locations) magnetic shields, based on preliminary tests that indicated this approach was practical. The stainless steel shields did not work well enough (became more magnetized over time than expected). Back-up of getting limited quantity of mu-metal shields was delayed in the Goddard shop for various reasons. An order was placed ($20K), but first shields did not arrive last week when expected. We cannot complete final integration of the light-transmitting fibers to the chassis without these shields. Schedule impact to integration. Tom Johnson spoke to the fabrication shop and they promised to deliver (overnight) the first 40 shields on March 14.

  9. Additional Vibration Testing • - A small frequency shift has been seen during X axis vibration testing of the qual chassis and the first 4 flight chassis (shifts ranged from 7 -11% which is about 8-13 Hz). The theory explaining this drop has been a slip/settling between the two PMT rails as they are not pinned together (and do not need to be pinned together) • We are confident it is not a failure or major fatigue but wanted to explain the shift if possible • Analysis predicts a frequency drop of 10% if the preload on the PMT rail fasteners is removed. This is consistent with our theory and test results. • Repeated x axis vibration testing using the Qual chassis confirms that the shift is due to settling of assembly, not failure. After numerous tests (-12dB, -6dB, full level and 4 at -6dB), the frequency dropped from the initial level of 97Hz to 87Hz, with no change seen following the full level test. • This test was not part of our schedule.

  10. CMMI ACD is one of three projects chosen by Goddard management to participate in a NASA-Headquarters-mandated assessment of “Capability Maturity Model Integration” system (CMMI). CMMI is described as covering more topics than ISO. Michael Amato (Systems Engineer) and Lorna Londot (Configuration Management lead) were in CMMI training and workshops for four days last week. Tom Johnson was tied up for a day. Many members of the ACD team are preparing for extensive interviews and reviews of documentation, to be held next week. These are the same people who should be working on all the documentation (including the Acceptance Data Package) we need for upcoming reviews. Needless to say, the ACD schedule will take a hit.

  11. Other Issues • - IDD sheet with harness brackets LAT had requested we add reveal a possible conflict with a blanket ground plate we need to add to the BEA covers. • Sent LAT a drawing for them define any interferences so we can modify or move plate (or harness) if possible

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