[MUSIC PLAYING] The James Webb Space Telescope is made up of four instruments. But only one of them is being built in the United States. It's called NIRCAM or Near-Infrared Camera. To find out more about NIRCAM, we have with us the principal investigator for NIRCAM, Marcia Rieke. Marcia, what exactly does NIRCAM do? 

NIRCAM is both the science camera for short wavelengths for JWST, meaning it should take beautiful pictures like we've come to expect from Hubble. But it's also the facility wavefront sensor and is used to tell how to line up the telescope. NIRCAM is actually part of the telescope in making the telescope work right. 

What kind of science do you expect from NIRCAM. 

Oh, that's a question we could spend the next five hours on. But what we're expecting is to find the first galaxies that formed after the Big Bang. We hope to find and characterize planets around other stars, more about how solar systems form, all kinds of things. 

We're standing above some sort of clean room. Marcia, can we get down there to get a closer look at what's going on? 

I think that can be arranged. And my team that's been building this, and aligning it, and calibrating it can lead you through what it does. 

What we have here is the optical metrology assembly for the NIRCAM instrument. We placed NIRCAM inside of the chamber. The system of mirrors takes a small beam from a star, and it expands it up, and then it makes the beam coming into the NIRCAM instrument the same size and shape as if it would be coming from JWST. 

Why do you have a chamber for NIRCAM? Why not just have it connected out here? 

We want to simulate the operational environment that the NIRCAM instrument will be in. It can see hot. It can see cold. It can see vacuum, all those different conditions that it would go through in its normal life. 

Thanks a lot for showing us your assembly. 

You're most welcome. 

The testing at the optical metrology assembly made sure NIRCAM could not just see a star clearly, but use its vision to do science and help align the telescope. After that phase was completed, NIRCAM went through some vibration testing before ending up here, at NASA's Goddard Space Flight Center. This time, it'll go through a number of checks, but it won't go it alone. NIRCAM's joined by the other science instruments on the Webb Telescope. Thanks for joining us for this edition of Behind the Web. 

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