NASA’s beleaguered James Webb Space Telescope (JWST) is facing yet another delay, and will not launch until March 2021. That’s 10 months later than the tentative schedule that the agency announced just three months ago . To meet the new target, NASA must convince lawmakers in Congress to approve the mission’s higher price.

The space agency estimates that the latest delay will add US$800 million to the telescope’s cost, on top of the $8 billion Congress had already approved for its development. NASA plans to make up that shortfall in part by using money that had been intended to support the telescope’s science operations in space. Still, the delays will loom over the agency’s astrophysics budget, with unknown effects on the next big space telescope in NASA’s queue, the Wide-Field Infrared Survey Telescope (WFIRST).

“I’m not happy sitting here,” said Thomas Zurbuchen, NASA’s associate administrator for science, at a 27 June news briefing on the delay. But he said that ensuring a successful mission was worth the extra time and money.

“JWST should continue because of the compelling science and because of its national importance,” said Thomas Young, a retired executive with Lockheed Martin in Bethesda, Maryland. He oversaw an independent review of the telescope project that led to the new schedule and budget estimates.

Spending committees in both chambers of Congress have sharply criticized the JWST delays in reports accompanying bills that would supply NASA’s 2019 funding. “These slips in the launch schedule are an enormous disappointment to the Committee,” wrote an appropriations committee in the House of Representatives — and that was before the latest delay.

Errors add up

JWST is the most complex astronomical telescope ever built, and problems have piled up during the last stages of its development. The observatory is currently in a clean room at Northrop Grumman Aerospace Systems in Redondo Beach, California, where it is undergoing extensive testing prior to launch. Among other issues, various screws and washers came loose from the covers of its sunshield during acoustic testing.

Engineers made several errors at Northrop, including cleaning valves with the wrong solvent so that they later leaked, and not tightening the sunshield fasteners properly.

JWST has a 6.5-metre segmented mirror that will launch in a folded configuration and then unfurl like flower petals once it is in space. Its sunshield must also deploy without a hitch. The observatory is technologically more complex than the orbiting Hubble Space Telescope, whose primary mirror was ground incorrectly, a problem discovered only after launch. Astronauts fixed Hubble’s vision in low Earth orbit with corrective optics; repairs are not possible for JWST, which will orbit at a point in space 1.5 million kilometres from Earth.

Until last September, JWST had been on track for an October 2018 launch. Then NASA pushed the launch to June 2019, then May 2020, and now March 2021.

Decadal detour

The last delay, which NASA announced in March, prompted Zurbuchen to propose that the US astronomy community postpone its next ‘decadal survey’. This influential process, which takes place every 10 years, asks astronomers to decide what scientific questions their field should tackle and what facilities they should build to answer those questions. The next decadal survey is due in 2020, and preparations were well underway when Zurbuchen suggested delaying it until JWST could be launched.

But the two other agencies involved in the astronomy decadal survey — the National Science Foundation and the Department of Energy — did not want to put it off. And neither did most astronomers polled by the US National Academies of Sciences, Engineering and Medicine, which oversees the survey. In late May, Zurbuchen reversed his opposition to proceeding with the survey as planned, and it is now on track to meet its original deadline.

JWST is scheduled to go into space aboard an Ariane 5 rocket provided by the European Space Agency, from the Kourou launch facility in French Guiana.

Budget worries

How the JWST woes will affect the rest of NASA’s science missions is yet to be resolved. At particular risk is WFIRST, slated for launch in the mid-2020s. Just as JWST was the highest priority recommendation from the 2000 decadal survey, WFIRST was the highest priority in the 2010 decadal survey. Both are being developed by NASA’s astrophysics division. The Trump administration has proposed cancelling WFIRST, although so far Congress has come to its rescue with continued funding.

Delays in the JWST launch date will hit early-career scientists particularly hard, says Leigh Fletcher, a planetary scientist at Leicester University, UK, who plans to use JWST to study Jupiter. “Opportunities for new research positions and fellowships to exploit Webb data get pushed further into the future, sometimes beyond the event horizon of fixed-term job contracts,” he says.

In the long run, the telescope promises revolutionary science that cannot be achieved any other way, says Jason Kalirai, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, and the project scientist for JWST. In a recent paper, he reviewed the possible discoveries, such as probing the earliest galaxies in the Universe as well as the atmospheres of planets around other stars ¹ . “We need JWST to make the next big breakthroughs in astrophysics, and are willing to wait for it,” he says.