NASA reveals major delay for $8-billion Hubble successor

Doug Carpenter
March 29, 2018

Delays in the testing and integration of NASA's next space observatory, the James Webb Space Telescope (JWST), will push its launch back to May 2020, the agency announced today.

After an independent assessment of remaining tasks for the highly complex space observatory, Webb's previously revised 2019 launch window is now targeted for about May 2020.

"Webb is the highest priority project for the agency's Science Mission Directorate, and the largest global space science project in U.S. history", Robert Lightfoot, NASA's acting administrator, said in a release.

"We have briefed the congressional staff about the likelihood of passing this breach mark, and informed them that the observatory is complete", NASA Acting Administrator Robert Lightfoot said.

Specifically, NASA said testing of the telescope element and spacecraft element demonstrated that each system individually meets their requirements.


Webb is an global project led by NASA with its partners, ESA and the Canadian Space Agency. As a result of the most recent delay, the space agency could exceed its $8.8 billion Congress mandated cap for the telescope.

"Additional steps to address project challenges include increasing NASA engineering oversight, personnel changes, and new management reporting structures", NASA added.

The telescope's spacecraft element consists of a Northrop-built sunshield and a spacecraft bus and is slated to undergo environmental tests this year. For example, the JWST needs to fold up to fit inside the payload bay of an Ariane 5 rocket, and then deploy itself once it's in space.

"Webb has already completed an extensive range of tests to ensure it will safely reach its orbit at almost one million miles from Earth and perform its science mission". "Webb is a really complex machine and rigorous testing is required to have a high confidence of success", Zurbuchen said.

Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate, added: "Considering the investment NASA and our global partners have made, we want to proceed systematically through these last tests, with the additional time necessary, to be ready for a May 2020 launch".


University of California, Irvine astronomer James Bullock is chair of the James Webb Space Telescope users committee. "It's just a matter of putting the two halves together and getting the testing done of the total observatory".

Among the tests to which the telescope is subjected, Webb must be exposed to the vibrations, noise, and extreme temperatures similar to what it will experience during its launch and its mission.

Delays in testing the sunshield and problems with the in-space propulsion system have slowed work.

NASA, which has a history of cost overruns on worldwide projects, warned that a new cost estimate that may exceed the projected $8 billion development cost to complete the final phase of testing and prepare for launch.

The Hubble won't be around forever - the intrepid telescope is expected to come to the end of its life sometime in the coming decade - so having the JWST ready to succeed it is key to the future of space science on a grand scale. However, the space agency has announced that it has (again) delayed the launch of the long-anticipated telescope, that is hoped to shed light on Mars, and other foreign worlds.


NASA has substantially completed all of the hardware for the Webb project, which remains in two pieces before final assembly.

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