GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
GLAST Large Area Telescope:
Gamma-ray Large
Area Space
Telescope
Tracker Subsystem
WBS 4.1.4
Highlights in Progress Since the
January Review
Robert Johnson
Santa Cruz Institute for Particle Physics
University of California at Santa Cruz
Tracker Subsystem Manager
johnson@scipp.ucsc.edu
Tracker, WBS 4.1.4
1
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Outline
•
•
•
•
•
•
•
Overview
Results from January Review
Action Item Status
Changes Since January Review
Hardware update since January
Schedule and Cost
Summary
Tracker, WBS 4.1.4
2
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Tracker Overview
• 16 layers of tungsten converter foils.
Multi-Chip
Electronics
Module (MCM)
– 12 layers of 3% X0 converters
– Followed by four 18% layers
• x-y Si-strip detector pair closely
following each converter foil.
• Two additional pairs at the bottom
are needed for triggering.
• 19 stiff composite “tray” panels
support SSDs on both faces with
electronics on two sides.
19 Carbon-Fiber
Tray Panels
2 mm gap
Readout
Cable
CarbonFiber Wall
– Converters are on the bottom face, just
above the SSD plane
– 2-mm gap between trays
• Carbon-fiber sidewalls conduct heat
to the base and stiffen the module.
• Electronics are based on 2 ASICs, PC
boards, and custom flex cables.
• 31.6 kg mass per module.
• 10.5 W of power per module.
Tracker, WBS 4.1.4
3
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Tracker Production Overview
Module Structure (walls, flexures,
thermal-gasket, fasteners)
Engineering: SLAC, Hytec
Procurement: SLAC
SSD Procurement, Testing
Japan, Italy, SLAC
SSD Ladder
Assembly
Italy
Tracker Module
Assembly and Test
Italy
10,368
2592
18
Tray Assembly
and Test
Italy
342
342
Cable Plant
UCSC
Electronics Design,
Fabrication & Test
UCSC, SLAC
Tracker, WBS 4.1.4
648
Composite Panel & Converters
Engineering:
SLAC, Hytec, and Italy
Procurement: Italy
4
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Results from January PDR/Baseline Review
• The Tracker has an Experienced Project Team .
• The concept of the Tracker is well matched to the science goals
and utilizes mature technology.
• The design is well thought out and can be implemented within
the available time.
• A strong consortium of groups in Italy has taken the
responsibility for assembling and testing all the ladders, trays,
and towers. This is a crucial contribution to the Tracker which
is being executed in a very effective and competent manner.
• “Baseline the Tracker with Increased Contingency”
Tracker, WBS 4.1.4
5
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Action Item Status
Action Item
Response
1
Baseline the
Tracker with
Increased
Contingency
The current basis for estimating
Project contingency needed uses 25%
of the Tracker cost to go VS 18% in
January
2
Thoroughly evaluate Agreed – Plan in place
pre-production IC’s
3
Refine Assembly
and Test
Procedures
Agreed – In process
Tracker, WBS 4.1.4
6
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Changes Since January 02 Review
• The schedule has been revised to accommodate the overall LAT
schedule extension.
– Added time for additional ASIC submissions.
– Incorporated a more conservative schedule for Tracker module
production with the Italian groups.
– Critical Deliveries:
• Modules 3, 4 available March 29, 2004, with 11 weeks of float.
• Modules 15, 16 available August 4, 2004, with 7 weeks of float.
• Budget
•
– Estimated cost at completion increased $180K
MOA with Italy
– INFN ready to sign and has been providing the requested funding
and covering for the delay in ASI approval.
– ASI has not yet signed but has recently begun funding Tracker
work with approval of $800k for FY2002.
Tracker, WBS 4.1.4
7
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Prototype Tower Module
• Mechanical prototype loaded with
dummy SSDs.
• Includes flexure interface to the
Grid.
• Used to test and evaluate
assembly methods.
– Assembly worked well, but tray
tolerances were not quite to
specification. Tray assembly
tooling has since been revised
and specifications met.
• Vibration and Thermal testing:
– Single panel: LAT-TD-759. 
– Grid-to-tower interface
thermal cycle: report in
progress. 
– Random vibration of the full
module: LAT-TD-788.
Problems (see following)
Composite trays and mass models
of the prototype tower, before
mounting of the sidewalls.
Tracker, WBS 4.1.4
8
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Vibration Test Problem #1
• Some screws attaching the sidewalls to
the bottom tray backed out during
transverse-axis qualification-level
random vibration. This problem was
solved (as verified in a retest):
– Replace hex heads by Torx-Plus to
enable tightening to the full
specification without stripping the
heads.
– Double the number of screws in the
non-MCM sides of the bottom tray.
– Add aluminum washer-inserts to the
sidewalls for these fasteners.
• We also plan to use a secondary locking
mechanism for the screws in the final
assembly, as extra insurance.
Tracker, WBS 4.1.4
Full module
instrumented for
thrust-axis
vibration
9
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Vibration Test Problem #2
• In the first test, a hairline crack formed in the bottom-tray
closeout between the edge and a corner-flexure fastener.
• In the second test suite at transverse-axis qualification levels
the cracking increased and the problem propagated to all 4
corners, breaking loose the corner-flexure mount inserts. (The
mid-span flexures all held fast.)
• Remediation in process:
Cracking as seen after
– Analysis to make sure we
the second test suite.
–
understand the failure and the
cure.
– Remove light-weighting cutouts
in the bottom tray and increase
its height by 5 mm.
– Reinforce each corner with a
bonded metal bracket.
Remediation Plan presented to
Project ART.
Tracker, WBS 4.1.4
10
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Tracker ASICs
• The second run of the GTRC and GTFE ASICs needed to be
resubmitted:
– GTRC V2:
• Missing rule in the Tanner DRC led to a short in the memory.
• Although complete chip was simulated with Synopsys Timemill,
clock skew margins were not sufficient for the IC to function
at nominal supply voltage (Tanner does not extract the clock
network as a distributed RC network).
– GTFE Vf: a minor modification was not verified by simulation due to
misunderstanding, missing an error that removed the baseline
restoration.
– GTFE Ve: the same missing DRC rule led to a nonfunctional analog
chain.
• Remediation:
– Careful crosscheck of the DRC rule-set against the Agilent vendor
rules and use of the MOSIS DRC checking service.
– Improved pre-submission procedural control.
– Controlled row-wise clock routing in the GTRC core.
– Submission of a back-up GTRC version without RAM.
Tracker, WBS 4.1.4
11
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Tracker ASICs
• The digital section does function in the GTFE Ve & Vf chips,
allowing substantial testing to proceed:
– Probe-card testing of the GTFE using the full set of test vectors
developed according to LAT-TD-247.
– Testing on the mini-MCM using GTRC V1 chips.
• Several problems were addressed in the versions in production:
– Proper response in the GTFE to undefined op-codes.
– Logic errors in GTFE register loading.
– Protection resistors in the I/O pads led to unreliable operation at
the full 20 MHz.
– Clock skew issues in the GTRC.
– DRC errors and the GTFE Vf comparator bug.
•
Chips presently in fabrication (Due August 22):
– GTRC with custom RAM and GTRC with Flip-Flop RAM (both usable
for flight).
– AC and DC coupled GTFE versions.
Tracker, WBS 4.1.4
12
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Electronics Testing
• Several “mini-MCMs” are under test at UCSC and SLAC, using
the V1 GTRC and Vf GTFE chips.
•
•
•
– Using COM card, interface board, and Python script at UCSC, to
develop the test station for MCM production.
– Using 2 COM cards, TEM, and SCL script at SLAC to debug the
ultimate readout scheme.
Mini-MCM has been interfaced with flight like Tower Electronics
Module(TEM) to verify functionality and interfaces. Continued use for
hardware and flight software development.
Parts qualification is in progress for poly-switches and HV caps.
Planning is in progress for radiation testing (total dose and FEE) after
the new chips arrive.
A mini-MCM loaded with 2
prototype front-end chips
and 1 controller chip.
Tracker, WBS 4.1.4
13
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Electronics Test Systems
• GTFE wafer probing:
– Operational on a manual probe station (undiced wafers will be
available end of August).
– Thorough set of test vectors for complete functional testing (see
LAT-TD-247).
– All of the test vectors have been exercised through the simulation
and actual chips (which uncovered the bugs fixed in the present
submission).
• GTRC wafer probing:
–
–
–
–
Complete hardware and software for manual testing.
Thorough set of test vectors (see LAT-TD-248).
No bare die yet to test it on (probes don’t fit V1).
Test vectors are presently being exercised through the simulation
and on the mini-MCM (with some restrictions, such as not being
able on the mini-MCM to cycle through the address space).
Tracker, WBS 4.1.4
14
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Electronics Test Systems
• MCM testing during production at Teledyne:
– Second-version interface board is in hand with enclosure plus a
better monitoring interface for power supplies and LVDS bias
levels.
– Test plan documented in LAT-TD-153 and LAT-TD-249.
– Test vectors are under development for functional testing, based
on extending the GTRC set.
– VME ADC modules were obtained, and software is in progress to
test the power supply voltages and the LVDS driver bias levels.
– Some software has been developed for threshold scanning (analog
performance tests) and tested on the d-version chip.
– Basic system, to be operated by its developers, will be ready for
testing the engineering-model MCMs in September.
• MCM burn-in station: layout of special cables is in progress.
Tracker, WBS 4.1.4
15
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Electronics Production
• Teledyne has successfully developed and tested the tooling for
bonding the pitch adapter flex circuit onto the MCM PWB.
• All parts and materials are present at Teledyne to begin
assembly of the dummy MCMs for the mechanical/thermal
engineering model tracker module. These modules will have all
parts, but with dummy or bad (GTFE Ve) ICs and with some
capacitors replaced with resistors to mimic the IC heat load.
• All of the molded plastic MCM carrying cases are in hand (in
fact, in sufficient numbers for the flight build). These are used
for MCM testing and burn-in following assembly, as well as for
storage and transport.
• Assembly of the dummy MCMs is beginning at Teledyne.
• Pisa is testing the MCM-tray interface, especially with thermal
cycling.
Tracker, WBS 4.1.4
16
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Engineering Model Tooling & Production
• Experience with the prototype Tracker module led to many
detailed changes in the assembly tooling designs for trays.
• Plyform (Italy) is now assembling EM composite panels with the
new tooling, and work is beginning to add the converters and
bias circuits.
• G&A Engineering (Italy) has assembled all of the dummy SSD
ladders and is now working on the live ones, expected completion
July 30, 2002. The electronics test system for the ladders is
operational.
• Tools for mounting the ladders and for assembly of the
top/bottom trays are in progress.
Tracker, WBS 4.1.4
17
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Procurement of Long-Lead Items
• Silicon procurement and deliveries on schedule.
– 2314 HPK SSDs have been received and tested in Italy.
– Production of flight SSD ladders will begin as early as
August 5, 2002 pending ladder assembly procedure review
and release.
• The carbon-carbon closeout material is on order from Alcomp
(US).
• In purchasing some items for the EM sufficient quantities for
the flight build were ordered to reduce costs:
– The molded MCM carrying cases.
– All of the screws for sidewall attachment.
Tracker, WBS 4.1.4
18
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Summary Schedule
FY 00
FY 01
FY 02
FY 03
FY 04
FY 05
JAFE
N MA
B ARPMA
R JU
Y JU
NA
L USGEOC
P NTODVEJA
C FE
N MA
B ARPMA
R JU
Y JU
N A
L USGEOC
P NTODVE JA
C FE
N MA
B ARPMA
R JU
Y JU
N A
L USGEOC
P NTODVEJA
C FE
N MA
B ARPMA
R JU
Y JU
N A
L USGEOC
P NTODVEJA
C FE
N MA
B ARPMA
R JU
Y JU
N A
L USGEOC
P NTODVE JA
C FE
N MA
B ARPMA
R JU
Y JU
N ALUOC
SGE TP
+ Key Milestones
PD R
C DR
Sh ip L AT
LAT I&T
+ Tray Assembly Development
+ Tray Mechanical
+ Electronics Design
+ SSD Product ion
+ Flight Electronics Assembly
+ Flight Trays Sub-Assembly
+ Final Assembly of Flight Trays
+ Qualificat ion Test
+ Flight Tower Assembly & Test Units 1 thru 14
+ Flight Tower Assembly & Test Unit s 15 and 16
Early B ar
LT-RV Summary Schedule
25JUL02 09:23
414 Tracker
Baseline
Progress B ar
© Primavera Systems, Inc.
Critical Activity
Tracker, WBS 4.1.4
19
O
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Key Milestones
Tracker, WBS 4.1.4
20
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Cost & Commitments
4.1.4 Tracker
($M)
10
8
5
3
0
FY00
ACWP
FY01
FY02
Actual Commits
FY03
FY04
BCWS
Budget + Commits
Tracker, WBS 4.1.4
FY05
21
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Cost Profile
4.1.4 Tracker
1,600
1,400
1,200
(K$)
1,000
800
600
400
200
0
FY00
FY01
LABOR
FY02
TRAVEL
FY03
FY04
FY05
MATERIALS & SERVICES
Tracker, WBS 4.1.4
22
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Workforce Plan
4.1.4 Tracker
30.0
25.0
FTEs
20.0
15.0
10.0
5.0
0.0
FY00
FY01
FY02
FY03
DOE + NASA Project
Tracker, WBS 4.1.4
FY04
FY05
Collaborators
23
GLAST LAT Project
DOE/NASA Delta Baseline/Preliminary Design Review, July 30, 2002
Summary
• The flexure-mount redesign effort is on schedule and should
not delay the Engineering Model schedule or the CDR.
• All other aspects of the Tracker design are complete. All
lowest-level drawings are in place as drafts, with 22 released.
Good progress on assembly and tooling drawings. See the
drawing tree on the Tracker web page.
• Some details of the production fixtures and processes are still
being tweaked and tested as the Engineering-Model build
progresses.
• Work is accelerating on documentation of test plans and
processes and production processes, in preparation for CDR.
• Overall, the Tracker development is progressing on schedule for
the subsystem CDR in January 2003 and the LAT CDR in April
2003.
Tracker, WBS 4.1.4
24