How Was Webb Built?

Sunday, February 14, 2016: 8:00 AM-9:30 AM
Coolidge (Marriott Wardman Park)
John C. Mather, NASA Goddard Space Flight Center, Greenbelt, MD
The James Webb Space Telescope (JWST) project, planned for an October 2018 launch, began in earnest with NASA Administrator Dan Goldin’s announcement to the American Astronomical Society in January 1996, for which he received a standing ovation. Webb was NASA’s second Administrator, responsible for the Apollo as well as for the Mariner missions to Mars and the Pioneers to the outer solar system.

The 6.5-m aperture telescope operates at a temperature of about 40 kelvin, protected by a 5-layer sunshield from the heat of the Sun and the Earth, and will orbit around the Sun-Earth Lagrange point 2, on the Sun-Earth line but 930,000 miles farther out than Earth. (JWST will avoid the Earth’s shadow.) Its instruments cover wavelengths from 0.6 to 28.8 µm with cameras and spectrometers, and can detect the heat of a bumblebee at the distance of the Moon.

NASA leads a partnership with the European and Canadian Space Agencies. In 2002, NASA selected teams for the observatory contractor (Northrop Grumman Aerospace), the assigned US Near Infrared Camera (NIRCam) instrument, and the science team. Europe is contributing the optics of the Mid Infrared Instrument (MIRI) and the Near Infrared Spectrometer (NIRSpec), as well as the Ariane 5 launch vehicle. The launch site is in French Guiana in South America. Canada is contributing the Fine Guidance Sensor (FGS) as well as the Near IR Imaging Slitless Spectrometer (NIRISS) instrument. The US is contributing everything else. The Space Telescope Science Institute in Baltimore will solicit and evaluate scientific proposals to use the telescope, as it does for the Hubble Space Telescope, and will make the data public.

The most difficult technology developments have been the ultra-light mirrors, the super-sensitive infrared detectors, the deployable sunshield, which has 5 layers of thin plastic, each as large as a singles tennis court, the closed cycle refrigerator to cool the MIRI to 6 kelvin, and methods were required to focus the segmented JWST after launch.

In 2016 the telescope and instrument module will be combined into a single unit at Goddard Space Flight Center and prepared for shipment to Johnson Space Flight Center for a verification of the thermal design and the end-to-end optical performance. The integration of telescope and spacecraft bus will be completed at the Northrop Grumman facility in Redondo Beach, California, before shipment to the launch site. The planned launch is in October 2018, with first scientific operations in April 2019.  The JWST carries fuel for 10 years of scientific operations.