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