What is the James Webb Space Telescope?
Picture the biggest telescope dish that technology can make. Next to it, a sunshield the size of a tennis court. Now, imagine folding them up like origami into a rocket and blasting them one million miles into space. This enormous engineering challenge is exactly what astronomers all across the world are facing as the James Webb telescope undergoes its final tests ahead of launch. And its aims are just as ambitious as it’s engineering. Izzie Clarke spoke to NASA's Bill Ochs about the mission...
"I worked Hubble for a long time. Hubble, when it was launched, rewrote the astronomy books and James Webb’s going to rewrite them again."
"The sunshade is about the size of a tennis court and that has to be unfolded in space."
"It’s mirror is seven times the collecting area of Hubble. You could put seven Hubble optics in the same surface area as the Webb."
"This thing I’ve spent 20 years working on is going to be strapped on a great big rocket and somebody’s going to fire it up into the sky. And that is a little bit nerve-wracking to think about."
Izzie - Picture the biggest telescope dish that technology can make. Next to it, a sunshield the size of a tennis court. Now, imagine folding them up like origami into a rocket and blasting them one million miles into space. This enormous engineering challenge is exactly what astronomers all across the world are facing as the James Webb telescope undergoes its final tests ahead of launch. And its aims are just as ambitious as it’s engineering.
Bill - We want to go back and look at the very beginnings of the universe.
Izzie - That’s NASA’s Bill Ochs. He’s the project manager of James Webb, overseeing every step of the telescope’s mission - from design development and terrestrial testing, right through to on orbit operations.
Bill - We’re want to back and look at how the first galaxies, stars and planets were formed. In addition, we also want to be able to go look at some of the exoplanets that have been discovered recently. We’re able to determine if they have the basic elements of life. We can’t really see little green men running around on those planets, but we can see if they have the basic elements for life as we know it.
Izzie - how exactly is this telescope hoping to explore this?
Bill - To achieve our scientific goals there’s a couple of different things you want to be able to do first. We have to be an infrared telescope - as light travels through the universe it goes from the visible light, and as the lightwaves lengthen, it shifts into the infrared part of the light spectrum. We also have to be really big to have a lot of light collecting power, so our primary mirror of our telescope is about seven times larger than Hubble’s primary mirror. That drives a lot of different technologies. We have to be able to fold our mirror up so it fits inside the rocket. Since it’s infrared, it has to be kept really really cold, and we keep it cold passively with this large sun shield that’s about the size of a tennis court. Think of it as a large umbrella. All of those things give us the ability to make the discoveries that I have mentioned earlier.
Izzie - For this missions predecessor, Hubble, astronomers and engineers were able to tweak and repair the spacecraft and equipment along the way. But once JWST is in space, that’s it. There’s nothing else that can be done. It has to be right first time.
Bill - We can’t do the type of servicing they did on Hubble. But Hubble, I always tell folks, it’s very unique to NASA. Not all of our satellites are serviceable, that’s probably the only one that’s really had a lot of servicing, but we’re much more like a traditional NASA mission where it is not serviceable. We test, test, and retest; we simulate, simulate, and resimulate to really put it through a very strenuous test programme with a lot of integrity. There’s not much else you can do.
Izzie - How far out is orbit?
Bill - We’re unique, we’re not like Hubble that’s in a low Earth orbit that was accessible by the Space Shuttle for servicing. We’re going to be about a million miles from Earth, out past the Moon at a point called the lagrange point 2. We go out there for a couple of reasons: 1) again, we want to be really cold; we want to get ourselves as far away from the Sun. It puts the Earth between us and the Sun. It also helps with observing efficiency. Whereas Hubble was in orbit, you go round behind the Earth and the Earth will be between you and whatever you are observing. Then you’ve got to come back around; we acquire than and continue your observation. We can do continuous observations; that saves time and we can make an observation the Hubble makes that may take them days, we can do in a matter of hours because of where we’re going to be located.
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