JWST
Mission CDR
Northrop Grumman Space Systems
Redondo Beach (CA)
April 10-16, 2010
Recent JWST Milestones
Mission Critical Design Review:
April 2010
Optical Telescope
Element (OTE) Review:
October 2009
Sun shield review:
January 2010
Integrated Science Instrument Module (ISIM) Review: March 2009
Mission CDR facts
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•
•
•
6 Days
Non
ITAR
>150 attendees
45 presentations
Enormous
amount of
information on
JWST, but…
Outstanding Issues (Pre Review)
• Sine vibe notching levels
– Discrepancies between Arianespace and ESA regarding approach to testing and analysis with respect
to launch vehicle requirements.
• Launch and ascent thermal margins
– Payload temperature changes during launch and ascent. ESA concluded that a fixed attitude solution
could be implemented with no performance impact, but it require extra flight programs to account
for varying sun angles as a function of launch date.
• OTE actuator life testing
– Life test gear motor and actuator used on Primary Mirror Segment Assemblies (PMSAs) and
Secondary Mirror Segment Assembly (SMSA) failed prematurely during their life tests. Under
investigation.
• JSC testing timeline and dynamic test environment
– The current estimates for the time required to complete all cryogenic testing exceeds the schedule
allocation (by a factor of ~2!) and needs to be optimized
– Add isolation into the system for problematic test modes
Standing Review Board
PASS
pending resolution of the following
1) Identified verification program and risk
reduction issues
2) Structural margin issues
3) Provide closure plan for all open Request For
Actions
4) Complete activities related to recovery of
Observatory thermal margins
1) Identified verification program and risk
reduction issues
JSC Tests: Current estimates exceed the schedule for
preparations, test and de-preps by about 100 days
Solutions:
1) “selected scope reduction”
2) “schedule allocation increase”
2) Structural margin issues
• JWST too large to be tested deployed:
NO END-TO-END TEST IS FEASIBLE
JWST Deployed Model is validated using a suite
of dynamic and structural tests conducted on
lower levels of assembly at Element, Subsystem
and Component levels.
4) Complete activities related to recovery
of Observatory thermal margins
• The sizes of the radiators associated with each
instrument have been readjusted to better
balance heat rejection margins
• Various sun/thermal shields added to match
50% margin
• Major improvements, i.e. the thermal balance
is highly sensitive to relatively small design
changes!
Final comments
• (JWST) is meeting all science and engineering
requirements for its upcoming mission.
• "The independent team conducting the review
confirmed [that] the designs, hardware and
test plans for Webb will deliver the fantastic
capabilities always envisioned for NASA's next
major space observatory.“
(E. Smith, JWST program scientist, NASA HQ)