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The Webb Update #6 - April 2009

Welcome to the sixth issue of the Webb Update, a newsletter to update the community about the James Webb Space Telescope.  Webb 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 receive the email newsletter, please visit our main Newsletter page for information on how to subscribe.

In this newsletter:

Integrated Science Instrument Module Approved for Full Scale Implementation
by Matt Greenhouse, ISIM Scientist

The Integrated Science Instrument Module (ISIM) Critical Design Review (CDR) was held during 9-12 March at Goddard Space Flight Center. This review was the first of three element-level CDRs leading up to the JWST Mission CDR. With the successful completion of this review, the ISIM element is approved for full scale implementation.

The JWST flight segment consists of three elements: ISIM, Optical Telescope, and Spacecraft, that together comprise the Observatory space vehicle.  The ISIM element contains four cryogenic science instrument systems, a fine guidance sensor system, and a number of mission critical supporting systems.

The three elements of the JWST Flight Segment
Figure 1.The three elements of the JWST Flight Segment.

More than 1000 charts and a library of associated documents were presented at the CDR covering all aspects of the ISIM hardware and software, their expected performance to requirements, integrated modeling, test & verification plans, as well as risk management, cost & schedule management. The review board was chaired by the GSFC Mission Assurance branch and included members of the JWST Standing Review Board as well as ESA and CSA representatives. “The review team was very impressed with the ISIM team’s significant progress, great technical expertise, and candid discussion of issues” said review team chairman Ted Hammer during the Board out brief. 


Table 1

With successful completion of this important review, the priority for the ISIM team is to complete work toward the start of ISIM level Integration and Test in the GSFC Space Environment Simulator. Science instrument systems are on schedule for delivery to GSFC during 2010. Upon delivery, the instruments will be integrated with their ISIM supporting systems at GSFC. Over a period of approximately 14 months, the ISIM element, in its entirety, will undergo thermal vacuum and other flight qualification tests using a telescope simulator within the SES chamber. The ISIM element will then be delivered to Northrop Grumman for integration with the telescope. The observatory, as a whole, will undergo cryo-vacuum testing at Johnson Space Center.

Figure 1
Figure 2. ISIM systems are located on the telescope and within the spacecraft.

Testing the MIRI Verification Model
by Gillian Wright, George Rieke and the MIRI Team

The verification model (VM) of the JWST Mid Infrared Instrument (MIRI) has had an extensive thermal-vacuum test over the past year at the Rutherford Appleton Laboratory in Oxfordshire, UK.  The VM is a flight-like version of the instrument, built for a variety of purposes including measuring accurately the heat load for the MIRI Cooler and developing methods for testing and calibrating the flight model (FM) instrument. The VM has sufficient functionality to explore virtually all features of the FM.

The data from testing are of sufficient quality for the MIRI science team to begin defining calibration files and algorithms for pipeline data reduction. The MIRI telescope simulator permitted point-source illumination of the imager and spectrometer anywhere in their respective fields of view, adjustment of the source temperature and flat-field illumination.

We have successfully demonstrated the end-to-end functionality of the data chain at cryogenic temperatures, exercised most of the detector features and modes, and verified that the optical performance is as expected from modeling. The MIRI VM test results build confidence in the design both in terms of science and of operations. All indications are that we have an instrument that will operate well and be capable of great science. The MIRI team is now concentrating on assembly and test of the FM instrument at subsystem level, with instrument integration planned for later this year.


see caption
Picture of VM instrument just prior to the start of testing

JWST Team Member wins Scientist of the Year in Canada

Dr. Rene Doyon, principal investigator for JWST’s Canadian-built Tuneable Filter Imager (TFI) and two of his former students, Christian Marois and David Lafreniere, were awarded the prestigious prize of Scientist of the Year by Radio-Canada (the country’s French-language public television network) in January 2009.


Rene Doyon
Photo: University of Montreal

A professor at the University of Montreal, Dr. Doyon was part of an international team of astrophysicists who became the first to photograph three exoplanets orbiting the same star. The discovery was made with the Keck and Gemini North telescopes in Hawaii, using Angular Differential Imaging (ADI), which reduces the brightness of a star in order to detect faint objects around it.

The Tuneable Filter Imager on the James Webb Space Telescope will use a similar technique, which should improve observations close to a hundred fold. This will give the TFI unique capabilities for detecting the first stars and searching for planets around stars outside our solar system. “If a planet like Earth were to transit in front of a low-mass star, this new technology would even be able to detect if the planet has water—a condition essential for the existence of life,” says Dr. Doyon.

In addition to the Tuneable Filter Imager, Canada is also building JWST’s Fine Guidance Sensor, which will measure position of guide stars with great accuracy, pinpointing stars to one millionth of a degree. Canada is also providing functional support of the science operations for JWST.

Rene Doyon

Letters b, c and d in this image show the positions of the three planets as photographed using ADI technology. The colourful mass in the centre is light residue from the immense halo of the star (Photo: NRC Herzberg Institute of Astrophysics).