It’s about time for the James Webb Space Telescope (JWST) to leave Earth and embark on its amazing mission to observe the infrared universe. I know a lot of folks are waiting anxiously for it to do so, myself included. If you go to the James Webb Space Telescope site, you will find a lot of material to check out about the instruments, the spacecraft, and the science that JWST can do.

In my last article, I wrote about the launch and the telescope, so today I want to focus on its mission. Essentially, it is to “uncover the hidden universe.” What does that mean?

The telescope and its instruments can “see” (detect) infrared light. Most of that light is in wavelengths we can’t see with our Mark I eyeballs. They limit our vision to a narrow part of the electromagnetic spectrum of light. There are things that occur in other wavelengths (such as ultraviolet or gamma or radio or infrared) that we’d never know about without specialized instruments such as JWST’s.

So, the “infrared universe” is out there, we just can’t see it that easily. At least, not without special instruments. Another thing about infrared (IR), is that Earth’s atmosphere interferes with the detection of that light. Sure, there are some infrared-enabled observatories on the planet, but they’re all at very high altitudes, where the atmospheric water vapor, for example, is quite low. The best place, really, to do infrared astronomy, is from space. And, the absolute best way to do it is to put the spacecraft well away from Earth, where the instruments can detect the light without any interference. And that’s what JWST can do.

What’s In the Infrared Universe

Just about everything in the universe has what you can think of as an “infrared signature.” That includes planets, asteroids, moons, worlds around other stars, the stars themselves, nebulae, and galaxies. It means that they all emit (or reflect) infrared light. That gives JWST a wide variety of objects and events to study, which makes it an exciting mission and a worthy partner to the Hubble Space Telescope (which is sensitive mostly to visible and some infrared and a little ultraviolet light).

Ancient Light and Modern Exploration

JWST explore the “current universe” and fill in some crucial information about objects and events “out there”. The telescope will be able to look far back in time as well as across space. That, for me, is one of the most interesting topics its observations will explore. It will help answer the question: “What happened in the earliest times in the universe?”

The chart here shows a timeline of the universe in very simple detail. It goes back to the very beginning of our universe, some 13.8 billion years ago. Now, we know the universe formed in an event called “The Big Bang.” It went through two phases. One was one called the Dark Ages when everything was… well… dark. That didn’t last very long, in the cosmic scheme of things, maybe about 200 million years. Then, the first stars were born and they began to shine.

This was a period called the “Epoch of Reionization.” It essentially means that things “lit up” again as the infant universe progressed. Those, early massive stars lived short, intense lives, and ended in spectacular supernova explosions. Their materials seeded the early universe with materials that ended up in clouds of gas and dust. Those were birthplaces for a second generation of stars. At around the same time, gravity began collecting these stars and nebulae into the first galaxies. The universe has continued to expand throughout its history. Along the way, more stars and galaxies have evolved to what we see today.

Observing that Infrared Universe

JWST is able to take advantage of a secret key to the ancient universe contained in infrared light. Light from those ancient events, stars, and galaxies, traveled across space for us to “see”. As it did, it was stretched by the expansion of the universe. So, those ancient stars may have emitted visible light, or near-infrared or even ultraviolet wavelengths. But, all that light got stretched well into the infrared part of the electromagnetic spectrum. Since JWST is very sensitive to the infrared spectrum, it’s going to act as a time machine. That will allow us to see what happened “way back when.” In essence, it’s going to probe the Epoch of Reionization and show us what those first stars and galaxies were like.

Stay Tuned

Currently, the JWST is scheduled for launch at 7:20 a.m. (Eastern Time) on December 24, 2021. If all goes well, it will ride to space aboard an Ariane 5 rocket from the ESA launch site in Kourou, French Guiana. You should be able to log into NASA TV or NASA Live to follow the launch and deployment activities. It’s going to be a great day for a launch, one that JWST scientists, technical staff, and launch are eager to see.

Well, kids, the James Webb Space Telescope (JWST, sometimes jokingly called the “Just Wait Space Telescope” due to the long time it has taken to get it to the launch pad) is finally atop its rocket and just about ready to go. The propulsion systems that will take it to its LaGrange orbit and keep it pointed correctly were all fueled a few days ago. Scientists are ready for it to go—heck, they’ve been ready for years. And, the technical crew is working round the clock on final arrangements for the launch, now scheduled for December 22nd. (UPDATE: it is now scheduled for launch no earlier than December 24th, due to a technical problem that engineers are working to solve.) People around the world will be watching from their homes, classrooms, planetarium domes, and science centers. There’s a growing collective sense of anticipation and we all hope this long-awaited telescope will finally take flight and begin to deliver data.

Beauty, Complexity, and Danger

The James Webb Space Telescope is a complex and (to me, anyway) stunningly beautiful piece of space hardware. There are thousands of pieces and parts that make up its spacecraft bus, mirrors, instruments, and solar shade that all have to work perfectly once the observatory is released to head for its LaGrange point. The idea of the solar shields and mirrors unfolding gracefully is nerve-wracking when you stop to think about it. They all have to deploy in the correct sequence, without a hitch. If they do, everything’s great. If they don’t—well, it just doesn’t bear thinking about, but it would be a disaster. I’m sure the NASA folk have worked through the scenarios so that they have a Plan A, Plan B, Plan C, and so forth, to deal with any problems. Still, there are many complex steps that have to happen perfectly before JWST is ready for science.

JWST: Launch and Deployment Rundown

First is launch, aboard an Ariane 5 rocket. Then, after it gets safely to space, the spacecraft fairing is ejected and the spacecraft is released. Very shortly after that, the JWST solar panel, which supplies power, is deployed. The next step is a mid-course correction burn to get the scope on the right path to L2—shorthand for LaGrange 2, a point in Earth’s orbit that allows the spacecraft to “follow” Earth (and face its night side) at a distance of 1.5 million kilometers. There are actually three correction burns to fine-tune the trajectory to L2.

The next big (and breathtaking) step is the sun shield deployment. That’s the one action that I’ve wondered about ever since I saw a full-scale model of the JWST at a meeting in Seattle a few years ago. It’s a very delicate but necessary piece of the spacecraft that protects the instruments from sunlight. That’s needed because JWST is infrared-sensitive, and the instruments need to be as cold as possible to do their work.

JWST: Unfolding the Mirrors

Only after the sunshield assemblies are in place will the mirrors themselves unfold. JWST doesn’t just have one mirror, it has a segmented main mirror and a single secondary mirror. The main gathers all the light of interest to the instruments inside the spacecraft and directs it to the secondary, which directs it to the instrument bay behind the main mirror. After the secondary is in place, the segmented mirror unfolds itself. That’s the second process that fascinates me—and I sure hope it all goes well!

JWST: Getting Ready for Science

All this happens while the spacecraft is on its way to deployment at L2. That trip will take about a month. Once it gets to its final destination the telescope starts a cooling process that takes roughly five months. It will also fine tune-its instruments, do final mirror alignments, and in general, get ready to do the science astronomers have waited to conduct for more than a decade.

That’s a little look at the process of getting JWST to its “workplace in space.” I’ll focus on JWST’s proposed science program in my next article. For now, though, check out NASA’s well-illustrated pages about the telescope, including a guided tour of its launch, unfolding, and deployment. And, tune in for launch if you can!