Speaking to reporters Tuesday, Thomas Zurbuchen, head of NASA's Science Mission Directorate, said the delay is required to deal with issues that arose as the telescope components were brought together at the Redondo Beach, Calif., facility of Northrop Grumman, the project's main contractor. Tests of some of the spacecraft's main components, particularly the tennis-court-size sun shield, have taken longer than expected. In addition, “a few mistakes happened,” Zurbuchen said, prolonging the integration and testing phase.
“Extensive testing is the only way to ensure the mission will succeed with high confidence,” Zurbuchen said. “Simply put, we have one shot to get this right before going into space.”
The project's standing review board predicted with 70 percent confidence that, with further tests, the telescope will be ready to launch in May 2020.
The massive space telescope, which has already cost $7.3 billion to develop, was a top priority in the National Academies of Sciences, Engineering and Medicine's 2000 Decadal Survey. Designed to work in the infrared part of the electromagnetic spectrum, the JWST's gold-covered, 20-foot-wide mirror would collect the oldest light in the universe, allowing scientists unprecedented insight into the time known as “cosmic dawn.” It would also probe the mysteries of black holes and seek out signs of life on planets orbiting distant suns.
But much of the technology required for such a fantastic instrument didn't yet exist. The JWST's creators had to invent, among other things, a main mirror and a heat shield that could unfold like origami in orbit. The cost of the mission quickly ballooned past the initial projection of about $1 billion, and the launch was pushed back from 2007 to 2008, then 2009, then 2010, then 2011, then 2013, then 2014, then 2015 or maybe 2016. The journal Nature called the JWST “the telescope that ate astronomy.”
After nearly canceling the mission in 2011, Congress voted to cap all additional funding for the project at $8 billion. A new plan put the telescope on target to launch in 2018. But that date has since slipped to 2019 and, today, to May 2020 at the earliest.
Acting NASA administrator Robert Lightfoot said the exhaustive integration and testing process, which can feel excruciatingly slow at times, is needed to ensure that the JWST is functional when it arrives in orbit. Unlike Hubble, which was in low Earth orbit and could be repaired by astronauts when a flaw in its main mirror was revealed after launch, the JWST will be a million miles from Earth, four times as far as the moon.
“It's this really important balance between pushing and being considerate and absolutely thoughtful about where we’re going,” Lightfoot said.
According to Dennis Andrucyk, deputy associate administrator of the Science Mission Directorate, the launch schedule took hits after mishaps required the replacement of a transducer that was incorrectly powered, valves that were affected when the wrong solvent was run through the propulsion system and a catalyst bed that was overheated. Engineers are also working to fix small tears in the sun shield and slack in the cables that help it unfold. Meanwhile, each unfolding and refolding of the sun shield has taken twice as long as expected, further delaying work.
According to a recent Government Accountability Office report, Northrop Grumman staff are working three shifts, 24 hours a day, to handle the issues.
Andrucyk said Tuesday that NASA will increase engineering oversight of these final phases, including ensuring that a senior official from the Goddard Space Flight Center (where the JWST was built) is always present at Northrop Grumman. In addition, an independent review board chaired by retired aerospace executive Tom Young will review the project's schedule, helping to establish a firmer timeline for launch. NASA expects to give a full report to Congress in late June.
The delay will have ramifications beyond the JWST team. NASA will need to negotiate a new launch date with the European Space Agency, which runs the spaceport in French Guiana where the telescope is supposed to lift off. And astronomers who wish to use the telescope for research will now have until 2019 to submit proposals for experiments.
The ongoing drama with the JWST may also affect the outlook for the Wide Field Infrared Survey Telescope, a dark-matter observatory that was the top priority of the 2010 Decadal Survey. NASA is already weighing cost-cutting measures for the mission, which was recently projected to cost 12 percent more than its budget. And in his most recent budget request, President Trump proposed scrapping the mission (for now, Congress has decided to keep funding it).
But Zurbuchen said the two missions are different in design, if not in importance. “We’re not going to be in a situation where 10 miracles are required” technologically, as happened with the JWST, he said.
Still, he mulled whether the National Academies of Sciences, Engineering and Medicine should wait for data from Webb before finalizing the next decadal survey, which will set priorities for the 2030s and beyond.