Dec 23, 2021 7:00 AM

The James Webb Space Telescope Finally Prepares for Launch

After decades of hard work and controversies, NASA scientists ready Hubble’s massive successor for its mission to probe the distant universe.

In the mid-1990s, a team of scientists proposed developing a next-generation infrared space probe. Nearly three decades later, after overcoming engineering, logistical, and political challenges, the ambitious spacecraft envisioned as Hubble’s successor will finally blast off.

Dubbed the James Webb Space Telescope, or JWST, in honor of a former NASA administrator, it comes packed with the biggest mirror ever to fly in space, a huge sunshield, and a suite of cutting-edge instruments that will enable it to find new life-friendly planets, reveal the births and deaths of stars, and probe the early years of the universe. The massive undertaking has become a reality thanks to a collaboration between hundreds of scientists and engineers at NASA, the European Space Agency, and the Canadian Space Agency. Barring inclement weather or technical difficulties, it’s scheduled for launch on December 25 at 7:20 am Eastern time, atop an Arianespace Ariane 5 rocket from Europe’s Spaceport in Kourou, French Guiana, on the northeastern coast of South America. If that launch is delayed, the next window of opportunity comes 24 hours later.

“I am thrilled. When astronomers have a dream, we never know how long it will take for it to happen,” says John Mather, JWST senior project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. JWST is much bigger and more powerful than the Hubble and Spitzer Space Telescopes, he says. “If you were a bumblebee hovering at a distance between the moon and Earth away from the telescope, we would be able to see you.”

It’s also different in key ways. While JWST currently fits compactly within the rocket’s frame, the telescope will unfold in space. A gold-coated segmented mirror of 18 hexagons will span 21 feet in total. A five-layer, diamond-shaped sunshield will unfurl to the size of a tennis court, to block out excess light that might hinder the search for exoplanets and other faint cosmic objects.

Unlike Hubble’s optical view of the universe, JWST will focus on infrared wavelengths so that it can penetrate gas and dust clouds to image distant objects. But infrared light is essentially heat radiation, so its ultra-sensitive detectors can’t be contaminated with any other heat. To minimize its own radiation, the telescope will be chilled to colder than -380 degrees Fahrenheit, which is barely warmer than absolute zero. And it will be sent nearly a million miles from home, to a point where it will take minimal fuel to counteract the gravitational pull of the sun and Earth, and where the shield will be able to effectively block their light.

The telescope’s high-resolution near- and mid-infrared cameras, as well as spectrographs, which spread the measured light into its component wavelengths, will zoom in on the atmospheres of nearby planets and on dust-enshrouded stellar nurseries. They’ll also probe some of the first galaxies to form in the early universe, which have never been seen by humans before. Once JWST becomes fully operational in mid-2022, it will beam hundreds of gigabytes of data every day back to scientists on Earth, and it will be in continual communication through the Deep Space Network, an international array of giant antennas managed by NASA’s Jet Propulsion Laboratory. Its mission is expected to last five years, at a minimum.

Scientists will try to use the telescope to solve one of the strangest puzzles of the cosmos: the fact that no one can pin down the rate at which the universe is exploding outward. Measurements of nearby pulsating stars called Cepheids, which can be used like milepost markers, and measurements of radiation from the early universe don’t give the same answer. “Many of the current issues in measuring distances using Cepheids, JWST will allow us to overcome them immediately, which is pretty exciting,” says Wendy Freedman, an astronomer at the University Chicago who’s leading a research program on the universe’s expansion rate that will use the telescope’s near-infrared camera. Hubble transformed the field decades ago, and now JWST could do so again, if Freedman and her colleagues’ finally resolve the cosmic discrepancy. “I’m really looking forward to that jump in technical capability,” she says.

Other astronomers will use JWST to probe the early universe. “Our goal is to map a large area of the sky and detect thousands of galaxies within a few hundred million years after the Big Bang,” says Jeyhan Kartaltepe, an astronomer at the Rochester Institute of Technology and lead scientist of COSMOS-Web, the largest program taking advantage of JWST’s first cycle of observations. It will survey a square section of the sky three times the area of the moon and study half a million galaxies. Kartaltepe and her colleagues did their best with Hubble’s cameras in the past, but Hubble could “only” see objects some 25 billion light years away. That meant that the earliest galaxies, heretofore unobserved and potentially very different from our Milky Way, have remained a mystery.

The massive telescope has also had its share of massive controversies, particularly over its cost and delays. Twenty years ago in a decadal survey, during which a team of experts organized by the National Academies of Sciences, Engineering, and Medicine produce a heavy report that ranks the next big projects in space science, they chose to make building the James Webb Space Telescope a top priority, as they had similarly prioritized its predecessors, including Hubble and Spitzer. But while NASA originally planned its launch for 2007, that date was repeatedly pushed back. Early estimates put the budget at less than $1 billion in today’s dollars, but the price tag continued to blow up, eventually reaching $8.8 billion, not counting about $1 billion for its future operating costs. Members of Congress called for an investigation into its spiraling costs and delays in 2010, and even threatened to kill its funding in 2011.

“When we started, our boss was very eager to push us to do something very quickly and much cheaper than usual. We tried, and then later we said, ‘Actually that’s not possible. We don’t want to work on this for 10 or 20 years and then take a chance that it might not work,’” Mather says. He and his team left nothing to chance, testing thoroughly and developing redundant versions of systems whenever possible. Other telescopes, like Hubble, also faced multiple delays and big cost increases, he points out. And its first images were blurry, a problem that astronauts had to fix in orbit. But today those early problems have been long forgotten; what people now remember are the telescope’s spectacular photos of the birthing clouds of stars and neighboring galaxies.

More recently, some astronomers and astrophysicists have argued that NASA should rename its new flagship observatory. In a March opinion piece in Scientific American, four scientists argued that in the 1960s its namesake was aware of, if not complicit with, “lavender scare” policies within the federal government, including NASA. Analogous to the anti-Communist “red scare,” these policies pushed many LGBTQ workers from their jobs at federal agencies.

Those authors, as well as more than 1,700 others in an online petition that was circulated following the publication of that opinion piece, called for the telescope to be renamed. Their objections prompted NASA to conduct an internal investigation in June. The agency didn’t release the results of that probe, but on September 27, current NASA administrator Bill Nelson sent a short statement to some news outlets: “We have found no evidence at this time that warrants changing the name of the James Webb Space Telescope.”

“I think that NASA could’ve done a lot better with their promises of transparency,” says Sarah Tuttle, a University of Washington astronomer and one of the authors of the op-ed. “I certainly hope in the future that NASA will consider actually instituting a community process as we name and launch more exciting big flagship missions.” She and other space scientists lament the James Webb name as an unfortunate distraction from the science the telescope will enable; they proposed alternatives like the Harriet Tubman Space Telescope and the Just Wonderful Space Telescope.

“Our focus should be on the tremendous power of this amazing facility that people have worked their whole careers on building. To have it bogged down with an element of controversy isn’t good for anyone involved,” says Caitlin Casey, an astronomer at the University of Texas at Austin who coleads the COSMOS-Web collaboration. This group changed the name of their own research program from COSMOS-Webb, and Casey now refers to the telescope only by its acronym.

Now that the telescope has finally arrived, everyone’s excitedly—and nervously—focused on its launch. Minor hiccups involving the tool for attaching the telescope to the top of the rocket, and involving a communication issue between the observatory and the launch vehicle system, delayed the launch, which was previously scheduled for December 18.

Assuming the launch goes according to plan, astronomers will then have to wait about six months until space science’s biggest Christmas present opens up and begins to witness new cosmic marvels. First, NASA engineers and their international colleagues have to follow an hourly step-by-step process for unfolding the telescope, moving it into position, cooling it down, and checking every part of every instrument, Mather says. He expects the scientific observations to start by the beginning of summer.

Hubble, which flies in low Earth orbit, has needed frequent servicing by astronauts over the years, and, as of late, it has been prone to hardware problems. For JWST, there can be no repairs in space because it will be so far away. Since no one can float up to JWST with a screwdriver, engineers have to hope that all their testing and backup systems will be enough. They have also developed methods for adjusting the telescope remotely, when needed. For example, scientists on the ground can precisely align the telescope’s mirrors, which are each attached to seven mechanical motors.

Astronomers believe JWST will not just benefit science, it will be a boon for communicating that knowledge to people who are curious about distant worlds, the lives of stars, and the beginning of the universe. “I think the images will be just as iconic and transformative as Hubble images, if not even more,” Casey says. “I’m going to be really thrilled to see them, and I think the public will really be captivated by them.”