Webb Project History

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Early design concepts for Webb, known at the time as the Next Generation Space Telescope, already incorporated a segmented mirror, an “open” design, and a large sunshield. CREDIT: NASA.
Even before the Hubble Space Telescope’s launch in 1990, astronomers began posing the question: What is the next step after Hubble?

In September 1989, the Space Telescope Science Institute (STScI) and NASA co-hosted the Next Generation Space Telescope Workshop at STScI, bringing together more than 130 astronomers and engineers. The group proposed that NASA investigate the feasibility of a 10-meter, passively cooled, near-infrared telescope in a high-Earth orbit or a 16-meter telescope based on the Moon to study galaxies at high redshift.

In 1996, an 18-member STScI committee led by astronomer Alan Dressler formally recommended that NASA develop a space telescope that would view the heavens in infrared light—the wavelength band that enables astronomers to see through dust and gas clouds and extends humanity’s vision farther out into space and back in time. It would have a mirror with a diameter of more than four meters, and operate in an orbit well beyond Earth’s moon.

Three teams made up of scientists and engineers from the private and public sectors met to determine whether NASA could realize the committee’s vision. All three came to the conclusion that the proposed telescope would work. NASA agreed in 1997 to fund additional studies to refine the technical and financial requirements for building the telescope. By 2002, the agency had selected the teams to build the instruments and the group of astronomers who would provide construction guidance. Also in 2002, the telescope was formally named the James Webb Space Telescope, after the NASA administrator who led the development of the Apollo program.

From Vision to Reality

Engineers and astronomers innovated new ways to meet the Webb telescope’s scientific demands, as well as a mission at an unserviceable distance from Earth. Unlike Hubble, astronauts will not be able to repair and upgrade the telescope.

Construction on Webb began in 2004. In 2005, the European Space Agency’s Centre Spatial Guyanais (CSG) spaceport in French Guiana was chosen as the launch site, and an Ariane 5 rocket as the launch vehicle. By 2011, all 18 mirror segments were finished and proven through testing to meet required specifications.

Between 2012 and 2013, Webb’s individual pieces, constructed in a variety of locations, began to arrive at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. In 2013, construction of the sunshield layers began. From 2013 to 2016, Webb’s science instruments were subjected to numerous tests of extreme temperature and vibration. From late 2015 to early 2016, all 18 of Webb’s individual mirrors were installed on the telescope’s backplane structure to assemble the 6.5 meter (21.3 feet) mirror.

In 2017, the mirrors and science instruments were connected and tested, then shipped to NASA’s Johnson Space Center in Houston, Texas. Additional environmental tests of the coupled telescope and instrument assembly occurred in a giant thermal vacuum chamber at Johnson in 2017, withstanding Hurricane Harvey in late August without a delay in schedule. Final assembly and testing takes place in 2018 and 2019 to ensure that Webb will perform its complex deployment unfolding and scientific mission perfectly once in space, since it will be farther away than humans have ever travelled and will not be able to be serviced. Webb will be launched from CSG in 2021.

Webb Project Timeline


The Space Telescope Science Institute (STScI) and NASA co-host the Next Generation Space Telescope Workshop at STScI. The focus was the science and technical capabilities of an observatory that would follow the Hubble Space Telescope after it was decommissioned, which was estimated at that time to be 2005.


An STScI committee recommends a significantly larger telescope capable of observing infrared light.

NASA selects Goddard Space Flight Center and STScI to study the feasibility of the Next Generation Space Telescope. Three independent government and aerospace teams determine that such an observatory is feasible.


NASA selects teams from the Goddard Space Flight Center, TRW, and Ball Aerospace to fine-tune the telescope’s technical and financial requirements.


Lockheed Martin, Ball Aerospace, and TRW (also partnering with Kodak and ATK) conduct Phase A mission studies, including preliminary analysis of the design and cost.

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Webb’s telescope structure fully deployed in the clean room at NASA Goddard. CREDIT: NASA, Chris Gunn.


Based on two Phase A studies, NASA selects the design of TRW/Ball Aerospace to continue in Phase B detailed design studies, which examine the performance and cost of the chosen design.

The telescope is renamed from the Next Generation Space Telescope to the James Webb Space Telescope.

In Phase B, TRW and Ball are awarded the observatory contract, but changes follow immediately. Northrop Grumman acquires TRW, and works with Ball to develop the observatory during Phases B, C, and D.

NASA selects the flight science working group and the team responsible for developing the Near-Infrared Camera (NIRCam).


Construction begins on certain telescope parts that require extensive, long-term work—in particular, Webb’s science instruments and the 18 segments of the primary mirror.


NASA approves the use of the European Space Agency’s Ariane 5 rocket to launch Webb into space.


The science instrument teams for the Near-Infrared Camera (NIRCam) and the Mid-Infrared Instrument (MIRI) pass critical design reviews and initiate construction of the flight instruments. All Webb’s essential technologies are tested successfully under flight conditions.


NASA has the Webb mission reviewed by internal and external groups. The internal preliminary design review and external non-advocate review conclude that the plans and designs have reached the maturity needed for NASA to commit to phases C and D, which entail detailed design, procurement, testing, and assembly of the telescope and observatory components. Construction begins in earnest.


The Integrated Science Instrument Module (ISIM) structure, built to house Webb'’s four science instruments, arrives at Goddard Space Flight Center for testing.


Webb passes its mission critical design review, which signifies that the integrated observatory will meet all science and engineering requirements for its mission.


Webb’s mirrors are completed. They are beryllium coated in a thin layer of gold, and have passed cryogenic testing, which exposed them to the frigid temperatures they will be subjected to in space.


Goddard Space Flight Center receives two of Webb’s four science instruments, the Mid-Infrared Instrument (MIRI) and the Near-Infrared Imager and Slitless Spectrograph (NIRISS), as well as Webb’s Fine Guidance Sensor, from the European and Canadian space agencies. Webb’s secondary mirror and the first three primary mirror segments also arrive at Goddard Space Flight Center from Ball Aerospace & Technologies Corp.

Northrop Grumman and partner ATK finish constructing the center section of Webb’s backplane structure, designed to hold the telescope’s primary mirror segments.


The two side “wings” of Webb’s backplane structure are completed by Northrop Grumman and ATK. Webb’s two final science instruments, the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec), as well as the remaining primary mirror segments, are delivered to Goddard Space Flight Center.


Manufacturing of the spacecraft parts (such as fuel tanks, gyroscopes, and solar panels) begins.

Cryogenic testing of the Integrated Science Instrument Module (ISIM), including all four instruments begins, to demonstrate the performance of the instruments as well as the electronics used to communicate with the instruments.


Cryogenic testing of the Integrated Science Instrument Module (ISIM) is completed. The 18 primary mirror segments are mounted into the backplane, along with the secondary mirror and support struts. The primary and secondary mirrors are integrated with the aft mirrors and the ISIM to create the unit known as the Optical Telescope Element.

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Engineers conduct a deployment test for Webb's sunshield. CREDIT: Chris Gunn, NASA.


The Optical Telescope Element successfully undergoes cryogenic testing in a giant thermal vacuum chamber called Chamber A at Johnson Space Center.

2018 – 2020

The Optical Telescope Element is delivered to Northrop Grumman in Redondo Beach, California. The observatory, sunshield, and spacecraft bus become one unit, and the completed observatory undergoes final testing.


Webb is shipped to Kourou, French Guiana, for launch in 2021.

Updated: May 04, 2016