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
Soon after the Hubble Space Telescope's launch in 1990, a question began to arise: What was the next step?

Hubble was a resounding success, advancing scientific knowledge of the universe as it pushed at the boundaries of our vision. It was a good time to peer over the horizon and decide astronomy's next move.

In 1996, an 18-member committee headed by astronomer Alan Dressler recommended that NASA develop a space telescope to succeed Hubble. The committee was specific about what the telescope should do. The panel envisioned an observatory 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 4 meters, giving it greater sensitivity to light and the ability to see farther into space than previous telescopes. It would operate in an orbit well beyond Earth's Moon.

In the spring and summer of 1996, 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, tentatively named the Next Generation Space Telescope, would work.

Buoyed by these findings, NASA agreed in 1997 to fund additional studies to further refine the technical and financial requirements for building the telescope. By 2002, it had selected the teams to build the instruments and the group of astronomers that would provide construction guidance.

From Vision to Reality

Since then, the telescope has gone through many changes. Its name changed from the Next Generation Space Telescope to the James Webb Space Telescope, after the NASA administrator who led the development of the Apollo program. The telescope's design and instruments have been altered time and again as their designers encountered, then overcame, obstacles thrown in their paths by the harsh demands of a space orbit at such a vast distance.

Construction began in 2004. In 2005, Webb's launch was set for the European Space Agency's launch site in French Guiana, with the telescope carried into orbit aboard an Ariane 5 rocket. Manufacturing continued on Webb's major components and in 2009, the ISIM unit that houses all of Webb's science instruments was completed. By 2011, all 18 mirror segments were finished and proven through testing to meet their specifications. Webb's individual pieces, constructed in a variety of locations, began to arrive at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Between 2012 and 2013, all four of Webb's science instruments arrived at Goddard.

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 21-foot mirror.

In 2016, the mirrors and science instruments are being connected and tested, then shipped to Johnson Space Flight Center in Houston, Texas. Additional environmental tests of the coupled telescope and instrument assembly will occur in a giant thermal vacuum chamber at Johnson in 2017. Testing of the sunshield will also be completed in 2017. The telescope and instruments will be joined with the spacecraft bus and sunshield in 2018, and final tests of the full observatory will be conducted. Finally, Webb will be united with its launch vehicle and launched from French Guiana in 2020.

Webb Project Timeline


The Space Telescope Institute Council appoints a committee to study 21st-century space-astronomy missions.


The committee recommends, as a successor to Hubble, a significantly larger telescope capable of seeing infrared light. NASA selects Goddard Space Flight Center and the Space Telescope Science Institute to study its feasibility. 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 is 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 becomes Northrop-Grumman Space Technology, and later Northrop-Grumman Aerospace Systems, and works with Ball to develop the observatory during Phases B, C, and D. Kodak later becomes ITT, then Exelis, and now Harris, while ATK later becomes Orbital-ATK. 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–provided Ariane 5 rocket to launch Webb into its operating orbit.


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


NASA has the mission reviewed by internal and external groups. The internal "preliminary design review" and external "non-advocate review" concludes that the plans and designs have reached the maturity needed for NASA to commit to phases C and D. Phases C and D entail detailed design, procurement, testing, and assembly of 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. These tests will verify ISIM's ability to survive launch and the extreme cold of space, and to precisely hold the science instruments in the correct positions with respect to the telescope.


The James Webb Space Telescope passes its Mission Critical Design Review, which signifies that the integrated observatory will meet all science and engineering requirements for its mission. The sunshield also passes its critical design review, certifying that its design is complete and meets mission requirements.


Webb's mirrors are completed. They have been polished and coated in gold, and they have passed cryogenic testing, which exposed them to the frigid temperatures they'll 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 ATK and Northrop Grumman. Webb's two final science instruments, the Near Infrared Camera (NIRCam) and Near Infrared Spectrograph (NIRSpec), as well as the remaining primary mirror segments will be delivered to Goddard Space Flight Center.


Northrop Grumman tests a full-scale engineering model of the sunshield to demonstrate the precision folding and unfolding necessary to protect the mirror and instruments from heat once in space. 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 in order to demonstrate the performance of the instruments as well as the electronics used to communicate with the instruments.


Cryogenic testing of the 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.


The Optical Telescope Element is shipped to Johnson Space Center for cryogenic testing in a giant thermal vacuum chamber called "Chamber A." The spacecraft bus is connected to the sunshield.

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

2018 – 2019

The observatory, sunshield, and spacecraft bus become one unit, and the completed observatory undergoes one final round of testing.


Webb is shipped to Kourou, French Guiana, for launch in 2020.

Updated: May 04, 2016