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The Webb Update #4 - December 2007

Welcome to the fourth issue of the Webb update, a newsletter to update the community about the James Webb Space Telescope (JWST).  JWST will be the next flagship astrophysics mission for NASA and is planned for launch in 2014. A text version of this newsletter is emailed to a subscriber list when it is released. If you would like to subscribe to the email newsletter, please visit our main Newsletter page for information on how to subscribe.

In this newsletter:

Astrophysics in the Next Decade: JWST and Concurrent Facilities – Meeting Summary
by Peter Stockman, STScI, Science Organizing Committee Secretary

The conference, held September 24-27, drew almost 200 participants to Tucson to hear forty speakers and moderators discuss the prospects for their fields in the next decade and how the Webb and future facilities would advance them. The subjects ranged from the theory of the very first stars (Tom Abel) to the origins of our Solar System (David Jewitt). Over 40 posters expanded on these themes, with many describing new instruments or new mission concepts. Representatives from most of the major funding agencies described their plans for the upcoming decade: Guy Monnet (ESO), Eric Smith (NASA), Hiroshi Karoji (NOAJ), and Gillian Wright (representing ESA).


conference photo
Mike Shull, Harley Thronson, Matt Greenhouse,
and Chick Woodward at the Tucson meeting.

The Science Organizing Committee organized the conference such that each 40-minute presentation was followed by a 20-minute moderated discussion.  The order of topics was mixed to provide a wide range of science fields every day. Both these experiments were successful in captivating and engaging the participants.

We will publish the conference proceedings, including summaries of the discussions and poster abstracts in mid-2008. In the meantime, we are posting presentations and posters on the conference web site. For more information on the conference see: .

JWST at the Austin AAS Meeting
by Peter Stockman

The JWST project will have a major presence at the upcoming winter AAS meeting in Austin, TX, January 8-11. Northrop Grumman will unveil updates to the JWST sunshield and display samples of the sunshield membrane. Ball Aerospace will bring a full-scale aluminum version of a primary mirror segment. The STScI and GSFC booths will feature pictures of the observatory, brochures and Webb DVDs.

The Science Working Group has organized a JWST Technology Town Hall meeting on January 9 at 12:30pm.The topics will be the new JWST technologies that enable the science instruments: the HgCdTe and Si:As detectors and ASICs, and the NIRSpec Micro-Shutter Array . In addition to addressing the current project status and the upcoming Preliminary Design and Non-Advocate Reviews, the speakers will answer questions from the AAS members.

ISIM Component Completes Cryo-Thermal Distortion Test
by Pam Sullivan, ISIM Manager

The JWST project recently completed the cryo-thermal distortion test of the Integrated Science Instrument Module (ISIM) Breadbox structure at the Marshall Space Flight Center (MSFC). This test, which took place in the X-Ray Calibration Facility (XRCF), is a critical part of the ISIM structure verification and validation. The test was complex and challenging, requiring interferometric measurements of thermal distortions at the micron level over five thermal cycles from room temperature to 40K. Teams from GSFC, ATK, Ball Aerospace, University of Alabama Huntsville, and the Space Telescope Science Institute worked on-site at MSFC, in close cooperation with the XRCF staff, for about 134 days during the period April-August 2007, 62 days of which required round-the-clock support for test operations. 

isim The Breadbox, designed to simulate the ISIM structure, is a composite tube truss structure, 1.2m by 1.4m in size, and is fabricated using the same design details, materials, and fabrication techniques as ISIM.  The test of the Breadbox leveraged the Backplane Stability Test Article (BSTA) test in 2006 to the greatest extent possible by utilizing modified BSTA support structures, test and handling procedures, instrumentation, and support teams. However, unlike the backplane test, both in-plane and out-of-plane distortions of the Breadbox were measured.  The in-plane distortions were measured by distance measuring interferometers, while the out-of-plane distortions were measured by an electronic speckle pattern interferometer.

Based on preliminary data reduction and analysis, the Breadbox test was highly successful.  Data quality, coverage, and cycle-to-cycle repeatability were good to excellent.  Final data processing is underway in support of Breadbox finite element model correlation.  Ultimately, this will be a major element in the verification of the accuracy of the ISIM finite element models used to analytically predict thermal distortions of the structure during various mission phases.

For more information on ISIM, see

Preliminary design Review held for the JWST OTE
by Bill Hayden, JWST Systems Engineer

From Nov 27 to Nov 29, the JWST Optical Telescope Element (OTE) held its Preliminary Design Review (PDR) at Northrop Grumman in Los Angeles.  The joint review team included a panel of independent experts from both Goddard and Northrop Grumman.  Review participants also included members of the NASA Headquarters-chartered JWST Standing Review Board, and members of the Project's Optical Product Integrity Team, which is an advisory group of independent experts in large optical systems.  The OTE passed its PDR with no liens which is the official gate that authorizes the project to proceed to the OTE Critical Design Review (CDR) scheduled for early 2009. 

Many of the OTE subsystems had previously passed their individual critical design reviews, such as the Primary Mirror Segment Assemblies, because they include long-lead items that are critical schedule drivers.  Hence the quality of the OTE PDR reflected the unusually high maturity of the OTE design.  As with all NASA design reviews, a formal process was in place so that the review panels could submit requests for action which will be systematically addressed by Northrop Grumman before the OTE CDR. The OTE PDR predates the Mission PDR by 4 months, which is scheduled in April 2008.

OTE See for additional information.