Webb Update

Rachel Osten, osten@stsci.edu

Summer 2013 proved to be a busy time for the James Webb Space Telescope, and significant progress was made on several fronts.  Key hardware and instruments were delivered, and testing commenced.  Momentum is building in the Webb project. We are planning special activities for outreach to the community at the January 2014 American Astronomical Society (AAS) meeting in Washington, DC.

And then there were three: NIRCam delivered to GSFC

The Near Infrared Camera (NIRCam) joined two other Webb instruments—Mid-Infrared Instrument (MIRI) and Fine Guidance Sensor/Near-Infrared Imager and Slitless Spectrograph (FGS/NIRISS)—at the Goddard Space Flight Center (GSFC). NIRCam arrived on July 27, 2013, from Lockheed Martin Advanced Technology Center in Palo Alto, California.  Principal investigator Marcia Rieke led the team at the University of Arizona and Lockheed who built NIRCam.

NIRCam is the primary near-infrared imager on board Webb. It operates in the range of 0.6–5 microns.  In addition to science observations, this instrument also works as a wavefront sensor, confirming the precise alignment of the mosaic of 18 individual primary mirrors.

NIRCam will make essential contributions to accomplishing Webb’s science goals. It is a versatile instrument for direct imaging, offering a wide-field survey mode, a small-source mode, and a channel for coronagraphic imaging. The short-wavelength (SW) and long-wavelength (LW) channels cover 2.21 × 2.21 arcmin2, with two-pixel sampling of the diffraction-limited point-spread function at 2 and 4 microns. Because of its importance to the Webb observatory in wavefront sensing, NIRCam carries a redundant imaging module and focal plane assembly.

A wide variety of filters offer high-, medium-, and narrow-band direct imaging. A grism offers slitless spectroscopy in the 2.4–5 micron range, with spectral resolving power of 2000. Figure 1 compares NIRCam’s sensitivity to that of other ground- and space-based imagers on large telescopes.

JWST_update-1 JWST_update-2











After NIRCam arrived from the west coast at GSFC in Greenbelt, Maryland on July 27, 2013, an aliveness test was performed to verify the instrument’s responses to inputs (Fig. 2).  The next stop was vibration testing at the Applied Physics Laboratory in Laurel, Maryland. Formal delivery of NIRCam to GSFC is expected to occur in Fall 2013.

Other mission milestones

The Webb program recently achieved two additional milestones. The Near-Infrared Spectrograph (NIRSpec)—the last of Webb’s science instruments to arrive at GSFC—was shipped from Germany in September 2013 and arrived at GSFC on September 20, 2013. NIRSpec will join the other instruments at GSFC for integration into the science instrument module and subsequent testing in 2014.

On August 22nd, the primary backplane support of Webb’s hexagonal primary mirrors arrived at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for testing.  The backplane supports the mirrors, instruments, and other telescope elements.  For more information on this hardware development, see the accompanying article by Blake Bullock.

Testing, testing, testing JWST_update-3

The Integrated Science Instrument Module (ISIM) consists of the four science instruments and nine instrument-support systems. The integration of the FGS/NIRISS and MIRI instruments with the ISIM structure is complete, and the first of three thermal-vacuum tests started on August 29, 2013, at GSFC. The primary purpose of the first thermal-vacuum test was risk reduction—performing dry runs of critical test procedures to identify possible improvements in the testing procedures before the second and third thermal-vacuum tests, which will follow in 2014 and 2015.  This series of tests of the integrated science payload is designed to simulate Webb’s operating environment in deep space. Figure 3 gives a view of the inside of the thermal vacuum chamber at GSFC. This space-environment simulator tests the ISIM at 35 K. FGS/NIRISS and MIRI were in place for the first test; all four instruments will be installed for the two subsequent tests.


The winter 2014 AAS meeting in Washington, DC will offer several opportunities for the community to learn more about Webb.  There will be a dedicated session on Webb science on Wednesday morning, January 8, 2014, at 10 a.m., with speakers addressing key topics for Webb.  The list of speakers and subject areas is:

– Marla Geha, Yale University, galaxy evolution
– John Johnson, Harvard University, exoplanets
– Alicia Soderberg, Harvard University, supernovae
– Matthew Tiscareno, Cornell University, solar system
– Mark Wyatt, Cambridge University, star/planet formation

Wednesday afternoon, January 8, 2014, at 12:45 p.m., a joint Webb and Hubble town-hall meeting will be held. The speakers include Ken Sembach, head of the Institute’s Hubble Mission Office; Eric Smith, the acting director of the Webb program at NASA Headquarters; and Nobel Laureate Adam Riess, affiliated with the Johns Hopkins University and the Institute.

The Institute booth at the AAS meeting will host a number of interactive sessions with the science community. The NIRSpec team at the Institute has been constructing tools and algorithms to assist with the complex multi-object spectroscopy (MOS) mode of the NIRSpec instrument. There will be demonstrations of the planning tool for the NIRSpec microshutter array at the Institute booth to solicit community input to the Webb MOS observation planning process.

The meeting will also feature Google+ “hangouts.”  These are on-line chats during which scientists describe how they plan to use Webb in concert with other observatories.