GLAST Large Area Telescope: Planning Meeting September 3, 2003 AntiCoincidence Detector (ACD) Subsystem WBS: 4.1.6

Transcription

1 Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Planning Meeting September 3, 2003 AntiCoincidence Detector (ACD) Subsystem WBS: David J. Thompson Thomas E. Johnson NASA Goddard Space Flight Center Subsystem Manager/Instrument Manager AntiCoincidnce Detector 1

2 CRITICAL MILESTONE CHART 1 Critical Milestone Jul 03 Aug 03 Sep 03 Oct 03 Nov 03 Dec 03 Jan Feb Ma r Apr Ma y Jun Jul Aug Sep Oct Nov Shell Subassembly Analog ASIC 1 3. Digital ASIC 4. Base Frame Assembly 5. HVBS Flight Unit 6. PMT Flight Unit 7. Tile Detector Assemblies Clear Fiber Cables Mechanical Subsystem (ready for I&T) Free Flt Unit Functional Test ACD Functional Test ACD Pre- Environmental Review ACD Vibration Test ACD TVAC Test ACD Pre-Ship Review ACD Ship 17. ACD Ready for Integration AntiCoincidnce Detector 2

3 Lat Instrument ACD Milestones Tile Shell Assembly GLAST LAT ACD Summary Schedule Task Tile Detector Assembly 7/31/ CDR (S) I&T CDR EM2 CAL PER PSR Flt 10/15/04 Flt Spares Shell Assembly Flt Base Electronic Assembly Base Frame Assembly High Voltage Bias Supply Analog ASIC Digital ASIC Front End Elec. Cards DU DU TU EU (Rec V-6) (Rec V-2) Flt EU Test Flt Test Flt (GARC) Flt (GAFE) Flt Photo Multiplier Tubes Micrometeroid Sh./Th. Blkt Mech Subsys (ready for I&T) ACD I&T TSA Integration BEA Integration Flt (240) CAL Flt ACD Integration/Env. Test ACD Prep, Ship, RFI Env. Testing ACD Ready for Integration 10/15/04 ACD to LAT Integration AntiCoincidnce Detector 3 ACD to LAT Integration (ND Date) 10/25/04

4 Near Term Milestones - 3 Month Plan Milestone Description First System Test w/ one FREE Board, HVBS, PMTs and TDAs Base Frame Channel Fabrication start Complete Fab of TDA tiedowns Receive/Test Flight ASICs (rapid-package) Fab Flight HVBS PCBs Complete Flight Mechanical Drawings Complete Design on MGSE and EGSE Complete Assembly of Flight Shell Start Testing on BEA EU Date 8/15/2003 8/29/2003 9/30/2003 9/30/ /13/ /31/ /31/ /31/ /10/2003 Completed Ready for fabrication Status/Notes Drawings, procedures in signoff Test procedures and test equipment ready Vibration Testing complete. Currently in TVAC testing. New designer just started Receive Sep03; Strength test Oct03. We will test 3 HVBS eus during this test. Complete Fab of Clear Fiber Cables System Test w/ two FREE Boards, HVBS, PMTs and TDAs Complete Fab of Flight TDAs 11/20/ /28/ /31/2003 Connectors complete; work started on assembly Preliminary test Sept Completion December 03 by Fermi. Delay due to manpower Fermi. PMT Housings and Bonding to complete 9/5. Complete PMT Assembly 1/30/2004 PMT assembly area is ready. PMT Assembly to start 9/8. AntiCoincidnce Detector 4

5 Interdependencies 1. Funding IPO, availability of LAT resources, GLAST Project, FY03 carryover 2. ASICs LAT Electronics group support, Product Assurance (packaging, qual, screen, and test). Status on rapid package as well as flight packaging? 3. Delivery of FREE Boards and Parts to Electronics 4. EGSE/G3 Ongoing development with I&T and electronic groups 5. ACD/GASU Cable details and system clock testing. Need signed off and configuration controlled drawing for cables. 6. Grid to Base Frame installation Outline drawing and available date for installation AntiCoincidnce Detector 5

6 Flight Hardware Procurements 1. TDA s December completion, design problem could impact delivery. 2. ASICs Receive rapid packaged ASICs on?, Submit ASICs for flight packaging 1-2 weeks after receiving rapid packaged chips 3. FREE PWBs September/October procure, available November 4. Electronic parts Completed, problem with HV capacitor 5. HVBS Assy August Start February Completion. Problem with HV capacitor causes minor (~ 1 week) delay. 6. Shell Panels Late September completion 7. PMT parts All parts procured, all housings completed next week, RN PCB s due in soon, HV Cap will delay assembly completion. 8. Base Frame Mechanical Parts July-August, complete December 9. TSA Mechanical Parts July-August, complete December AntiCoincidnce Detector 6

7 Manufacturing Plans 1. TDA s Completed 2. ASICs qual, screen and test plan In review 3. FREE and HVBS using standard process 4. PMT Assy Plan In sign off 5. Mechanical Parts Using standard plans 6. Clear Fiber Cables Procedure in final review, beginning fab of EU units as well as training techs. AntiCoincidnce Detector 7

8 Unresolved Assumptions 1. Thermal Blanket interface (outline drawing) 2. Grounding (outline drawing and grounding plan) 3. Rates data (resolved in principle) 4. Link up date for Grid to Base Frame interface 5. EGSE cable lengths GASU to EGSE ~14m 6. GASU has to work in TVac and Vibration (with isolation) AntiCoincidnce Detector 8

9 New Issue #1 TDA design problem Interference between WFS and TDA tiedown at this point Three Potential Solutions identified. Move some TDA tiedowns Reduce bending radius of WSF Decrease size of TDA tiedown Potential impact to shell panels and TDA Tiedowns Good news is that Fermi staffing issue is under control, bad news is they have to refocus their efforts to helping solve this problem. AntiCoincidnce Detector 9

10 New Issue #2 High Voltage Capacitor does not meet requirements. Dielectric strength out of spec. Predicted life time of capacitor would be reduced by a factor of ~2.5 No life testing results available to verify predictions. Engineers expect that actual would be worse than predicted Long lead part (original quote of 12 weeks) Ordered ~16 weeks ago. Parts came in a little late and screening on first batch has just been completed Manufacture has agreed to replace part at no cost. Negotiating for a shorter lead time (~7 weeks may be possible) as well as keeping 40 of the original parts so that testing program can continue. Part is used in PMT assembly as well as HVBS s. Used on 2 nd (middle) resistor network board. This will delay PMT assembly completion. Work-a-rounds include installing all 1 st boards as well a reshuffling work for assembly techs. Will assemble qual PMTs using non-spec parts. Impact to HVBS will be minimal. Proceed with qual unit HVBS using non-spec part. AntiCoincidnce Detector 10

11 Issues and Concerns - updates Need for a final Qualification and Screening Plan for ASICs is a concern LAT has a general Q&S Plan for ASICs Issue has been the specific implementation (particularly testing) needed for the ACD ASICs Working with LAT Parts Control Board in consultation with Goddard parts engineers to finalize details of the plan. Agreed in principle, but documentation is still needed. Test boards are being designed. Shortage of test equipment at Goddard is a concern In particular, equipment needed for the ASIC Q&S program seems to be in short supply Working with Goddard local laboratory and Engineering Directorate to locate or repair needed equipment. Not much success so far. Requested Goddard funding (~$60K) for additional equipment. None provided yet, requiring unbudgeted expenditures to keep testing program on schedule. AntiCoincidnce Detector 11

12 Issues and Concerns - new Reduction of support for ACD TDA production at Fermilab is an issue. Accelerator shutdown, required vacation, and extended medical leave have seriously reduced the staffing available to continue the TDA fabrication. Issue appears to be resolved. Axiom operator (actually 2 this week) vacancy has been resolved. They will work a second shift if required to maintain schedule. Have been assured that this job is a high priority, second only to the beam shutdown. Alex and I will be going to Fermi next week. Reduction of support for ACD mechanical engineering at GSFC is an issue. Problem in another flight project (XRS on Astro E2) has siphoned off some of the time of ACD mechanical engineers Working with Goddard management to retain enough support to maintain schedule. Receiving additional support to backfill support lost to XRS ASIC Yield 50% yield at ambient temperature prior to thermal cycling or burn-in AntiCoincidnce Detector 12

13 Issues and Concerns - updated Late delivery of G3 Test Stand/EGSE from LAT Electronics and I&T is a concern Scheduled for August, recently slipped to November/December Planned for testing of multiple FREE cards and Electronic Chassis, scheduled for August - November Developing workarounds, using older G2 Test Stands and bench electronics. Interfaces are less like the flight interface, but should allow much of the testing. Developing the G3 software before the arrival of the hardware, to minimize the startup delay once the G3 Test Stands arrive. G2 will be testing flight hardware, need documentation. ACD cost increases and availability of FY03 funding is an issue Cost to Complete exercise identified increased costs for ACD Goddard Engineering Directorate has provided additional Civil Service support, replacing contractors with CS personnel wherever a qualified Civil Servant could be found. GLAST Project has offered some support. Additional ACD funding included in the current LAT request. AntiCoincidnce Detector 13

14 Open Design Issues - update OPEN: Outline drawing that defines some interfaces with LAT is still not complete (blanket attachment, grounding, cable tie-downs, optical survey mounts). Action Plan: Work with LAT mechanical design team to resolve open issues by August 29. Status unchanged. CLOSED: LAT Electronics group requested a change in the backshell of the connector to the ACD. This change requires a change in the bracket that holds the connector, and this bracket is a structural element. Modification should be straightforward, but must be analyzed. Action: Decided to stick with original design. CLOSED: FREE Board design updates and finalization. Action: Design complete and in fabrication. OPEN: Need updated interface loads following Grid design changes. Action Plan: Review ACD analysis when updated loads are received. ACD will not delay fabrication of mechanical components due to this open issue (slight risk in doing so). Status unchanged. OPEN: Discovered interference between some wave shifting fibers and TDA flexures. Action Plan: Re-design and re-analyze to resolve. AntiCoincidnce Detector 14

15 Mechanical and EEE Parts - update Mechanical Parts and Materials - ALL APPROVED PMTs Qualified, tested, and screened (final report in draft form now) EEE Parts FREE - 36 different part types; approximately 830 parts per board. All parts approved by PCB with the following exceptions. MAX145 and MAX5121 being qualified by GSFC parts group (chips provided by Calorimeter). ASICs in fabrication. S&Q plan is complete and has been reviewed by members of the PCB. Detailed GARC test procedure in review and draft GAFE test procedure is being circulated MAX494 was recently approved following radiation testing HVBS - 38 different parts types; 108 total parts per board 4 parts are not yet approved (DPA needed on 3 capacitors, screening needed for one wire) High voltage capacitor was rejected, did not meet specification Resistor network - 9 different parts types; 26 total parts One connector is not yet approved, waiting for screening AntiCoincidnce Detector 15