Transcript ppt)

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
[email protected]
[email protected]
GLAST LAT ACD FTF 3/17/05
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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.
GLAST LAT ACD FTF 3/17/05
2
Electronics Chassis Assembly and Test Plan
8X
Base Electronics Assembly (1)
Electronics Chassis (8) (4 double + 4 single)
Electronics Chassis
Assembly
EMI/EMC
Vibration
Thermal Vacuum
Qualification / Flight
Spare
Complete
Qualification
Qualification
12 cycles
(completed)
(completed)
(completed)
#1
Complete
Not planned
Complete
Complete
#2
Complete
Not planned
Complete
Complete
#3
Complete
Not planned
Complete
Complete
#4
Complete
Not planned
Complete
Complete
#5
Complete
Not planned
In progress
3/10/05 > 3/21/05
#6
Complete
Not planned
3/9/05>3/23/05
Descoped
#7
3/1/05>3/16/05
Not planned
3/11/05>3/25/05
Descoped
#8
3/2/05>3/17/05
Not planned
3/11/05>3/25/05
Descoped
GLAST LAT ACD FTF 3/17/05
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Schedule Flow
10/4 – 2/5/05
Qual
Electronics
Chassis
Environmental
Test
2/7 - 2/15
1st flight
chassis
Environmental
Acceptance
Test (8d)
6/10/04 – 1/28/05
descoped
Install & test
1st flight
Chassis onto
ACD
Vibration Test
(5d)
EMI/EMC Test
(9d)
4/20 – 4/22
Acoustic Test
(3d)
GLAST LAT ACD FTF 3/17/05
4/23 – 5/12
Thermal Balance/
Thermal-Vac
Test
(20cd)
4/12 (TBR)
PreEnvironmental
Review (PER)
5/13 – 5/14
Mass Properties
(2d)
2/16-3/23
2/28 – 3/18
2/15 – 2/22
Initial
TDA/TSA
I&T in B7
4/14 – 4/19
The remaining
Seven Flight
Chassis
Environmental
Acceptance tests (25d)
4/11 – 4/12
Install Thermal
Blanket &
MMS(4d)
5/17
Pre-ship
Review (PSR)
Assemble last 2
rows of
TDAs & WSF
(124-130, 224-230,
324-330, 424-430)
onto TSA
Install & test
remaining flight
Chassis onto
ACD
3/31 – 4/9
ACD Subsystem
Efficiency
Verification test
(include rotate
ACD 90 degree)(10d)
5/18 – 5/23
ACD ship
to SLAC
(5d)
3/24 – 3/30
ACD Full
Functional
Test(6d)
5/24 – 5/28
Post ship
Check out
(5d)
3/23/05
ACD
Integration
complete
5/28
ACD RFI
4
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..)
GLAST LAT ACD FTF 3/17/05
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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!
GLAST LAT ACD FTF 3/17/05
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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.
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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 lighttransmitting 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.
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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.
GLAST LAT ACD FTF 3/17/05
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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.
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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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