The long-awaited James Webb Space Telescope — successor to the Hubble Space Telescope — will now launch between March and June 2019.

James Webb Space Telescope primary mirror
The James Webb Space Telescope in the clean room with all 18 mirror segments in place.
NASA / Chris Gunn

The James Webb Space Telescope (JWST) promises revolution for astronomy. Its 18-segment, 6.5-meter mirror and infrared instruments will see the very first stars and galaxies forming in the universe, watch starbirth in nearby stellar nurseries, peer at exoplanet atmospheres, and directly image exoplanets themselves. The sensitive and sharp-eyed instruments will discern unprecedented detail in just about every aspect of astronomy.

Yet the JWST has had a troubled history. The now $8.8 billion scope was first proposed as a $1.6 billion mission to launch in 2011. Multiple delays and cost overruns prevented that from happening, and Congress threatened to cancel the program altogether, despite the funding already invested.

So in 2011, the year the telescope ought to have launched, NASA officials basically promised Congress that they would stick to a new $8.8 billion budget that would carry it would through commissioning. The launch date, officials said at the time, would be October 2018.

For years, development stuck to schedule and the telescope looked to be on track for its 2018 launch. But on Friday, September 29th, NASA announced in a press release delays in instrument integration would set back the launch date by several months, rescheduling the launch from French Guiana to sometime between March and June 2019.

“The Congressional cap is on the development (through commissioning) cost of Webb and not the launch date,” says program director of JWST Eric Smith (NASA). “No new funding for Webb will be required even with the launch date change.”

“Assuming the remaining integration and test steps proceed as planned for Webb, and no long launch delays are encountered in French Guiana,” he adds, “the Webb Program has sufficient funds to stay within its planned budget.”

The delay is due to delays in integration of various spacecraft elements, says Thomas Zurbuchen (NASA), associate administrator for NASA’s Science Mission Directorate. “The change in launch timing is not indicative of hardware or technical performance concerns.”

The telescope and science instruments are currently undergoing cryovacuum testing to mimic conditions they’ll see in space, orbiting the Sun with Earth but 1.5 million kilometers away, at the L2 Lagrangian point. So far the tests have gone as planned and the instruments are performing as required, Smith says.

The five-layered sunshield, which will protect the infrared detectors from sunlight, was fully integrated onto the telescope in August. The tennis court-sized sheets cool the spacecraft by 300°C across the 4.8-meter spacecraft body. And once the telescope is launched to its orbit — well away from any hope of repair — those sunshields will have to unfold perfectly for the telescope to work as designed.

The size and sheer complexity of the spacecraft, sunshield and all, are the drive behind the extensive testing that’s being done — better a functional telescope that’s six months late (well, six months and several years) than one that’s on time and doesn’t work!

So, what's next? First, engineers will test the spacecraft and sunshield, including deployment testing, as well as vibration and acoustics tests (which ensure the spacecraft and sunshield will survive launch intact). The final step, Smith says, is to integrate the telescope itself with the spacecraft. "After that integration, final testing of the fully assembled observatory will occur."

Watch the sequence of events now expected in 2019:


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Justin S

October 1, 2017 at 6:13 pm

Reading about the Webb Space telescope, I am concerned that it is far too complex. It is years behind schedule and billions over budget. If it is successfully launched, it will be in an inaccessible orbit. If anything goes wrong it will be unusable and unrepairable. I hope I’m wrong, but I predict it will not be successful nor will it meet its design specifications.

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October 2, 2017 at 10:20 am

I understand your cynicism Justin. I watched the animated deployment sequence several times. There is so very much that can go wrong with little to no hope of correction or repair. We have been here before though; some failures and some very astonishingly, victorious achievements; CASSINI!!,KEPLAR!, THE VOYAGERS!!!, and many others. I am hoping for the absolute best outcome because there are too many naysayers out there who would seize upon a failure as an opportunity to restrict science funding in the future.
JWST will hugely expand our understanding and future imagining of the truth of our place in the Cosmos just as Hubble and Cassini have done. That, I think, is a priceless benefit. Go forward JWST!

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Justin S

October 3, 2017 at 5:52 pm

Thanks for your comment, John. Alas, a cynic is what an optimist calls a realist. 😉

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Justin S

October 3, 2017 at 5:53 pm

I just turned 75 years old. I wonder if I'll live to see the JWST launched. I really hope it works! I've seen a lot of technical advancement in my time!

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October 8, 2017 at 1:04 pm

dear Justin, yours is not being a realist just because you confute bad odds based on a "feeling" of odd more difficult variables! (if you were the director of the program those feeling would have been way more realistic). But we totally know that you say that because your anti-jinxing the project as in your great old heart you wish success: and for that we love you so much.

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Anthony Barreiro

October 2, 2017 at 3:26 pm

"[B]etter a functional telescope that’s six months late (well, six months and several years) than one that’s on time and doesn’t work!" -- Indeed!

Given that JWST will be too far from Earth to be repaired or upgraded *with current crewed spacecraft*, I wish NASA would focus on developing the ability to get astronauts to L2, rather than going to Mars so we can all see video of a human raising a flag there. L2 is a lot closer than Mars, and we won't need to worry about humans contaminating JWST with terrestrial microbes.

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Justin S

October 3, 2017 at 5:56 pm

I agree! We need a "space pickup truck!" That is, a small craft capable of far orbit with a small crew and that can carry a few hundred pounds. The space shuttle was nice, but it was more like a dump truck. If you wanted to take a peanut to the ISS, you had to send the whole dump truck.

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October 2, 2017 at 4:37 pm

Amen to all of that!!

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October 2, 2017 at 9:25 pm

I'm firmly with you, Anthony, on this!

As we say back home in NZ... "Get it right, and you have to only do it once"!
Let's hope they get it right, and it goes on to have a lengthy and hassle free life-time.
There's a lot of fringe technology bolted onto that thing (lest we forget).

"Near enough isn't right, but right... is near enough".
Let's hope they really get it right!

Graham W. Wolf at 46 South, Dunedin, NZ.

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October 6, 2017 at 6:05 pm

The fact that it is not possible to go up and fix it gives me a cold feeling in the pit of my stomach. Look at how wonderful Hubble is now, but consider how many times it has been fixed since it went up. Why will JWST be any different?

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October 6, 2017 at 6:46 pm

Monica, Thanks for the update. I guess we are all waiting with baited breath and on tenderhooks that the launch and sequence of deployment works in the cryogenics of space. The cryogenic testing can only simulate the unfolding. Anthony and Justin, maybe the X-7B could do a special very long run to service the craft (but that would be classified)? I guess with so much time and money invested a failure would probably put an end to the Mars mission and maybe that would not be so bad, (maybe just send humanoid robots). Good luck JW from Oz..

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October 7, 2017 at 4:30 am

I too am concerned also about the fate, if that is the correct wording of JWST. I agree with the first posting. It is simply too complex a spacecraft.
That said. I think the engineers and all involved will make sure it does, what it say's on the tin. And that there are NO failures.

I hope the launch is successful and that it does operate to its full potential once in orbit.

From. The Cloudy UK.

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October 7, 2017 at 12:23 pm

Seems to me that NASA and their contractors have ample experience with automated sequences, like the "7 minutes of terror" of Curiosity's landing, that the Webb's mechanics are within their capabilities.
But you know, I just realized ... with all the rapidly progressing commercial space launch activity recently, undreamt of when the Webb was conceived and designed -- even Elon Musk talking of going to Mars in 2024 -- suddenly it doesn't seem quite so farfetched to think of eventually repairing Webb at L2!

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