[MUSIC PLAYING] The mid-infrared instrument or MIRI on the James Webb Space Telescope is unique in a number of ways. First of all, it looks at a different part of the electromagnetic spectrum than the other instruments do. It looks at mid-infrared frequencies. Second of all, it takes both pictures and spectra. To find out more about the MIRI, we have with us the European principal investigator, Gillian Wright. Gillian, it looks at the mid-infrared range of frequencies. What is mid-infrared? 

Mid-infrared means we look at longer wavelengths compared to what the other instruments do, which is described as near-infrared. It's better at looking through dust. It's also more sensitive to different colors of objects, lots of molecules that might indicate life on other planets. Those molecules make spectra in the mid-infrared. 

It takes pictures and spectra. Why the two? 

Yes, because to do our science, we want to be able to take both pictures and spectra. So I suppose in an ideal world, we would have had to mid-infrared instruments on JWST. But there wasn't space, so we built it into just one instrument that does both things. 

And I understand we have a real, honest to goodness MIRI right here at Rutherford Appleton Laboratory, right? 

Yes, we're all really excited because we've just finished putting the flight model of the instrument together. And we're about to start testing. 

So, Gillian, this is the MIRI, huh? 

Yes, this is the MIRI. This is the flight instrument. So we need to be very careful. MIRI deliberately has a very modular design so that each module-- for example, this box here-- can be built and tested by itself before we build it into the rest of the instrument. 

Did you build these modules all here? 

No, we had different modules built in different parts of Europe. Because that way we could use the skills of a lot of different institutes, all of which have very specialist knowledge about certain areas of how to do instruments. And we could bring it all together to create the MIRI. 

But the MIRI is both a spectrometer and an imager. 

Yes, that's right. So the spectrometer-- when it's this way around, the spectrometer sits on the top. But we can turn the instrument over so we could take a look at the imager. The light would come in here from the telescope. And it hits the mirror, which turns it and sends it to the middle of the instrument. Most of the light is then sent to the imager so that we can take pictures with the imager. And a very small fraction of the light is sent to the spectrometer for us to do spectroscopy. 

Gillian, thanks so much for showing us your MIRI. 

You're very welcome. 

As you can see, the MIRI is basically two instruments in one. And it will be able to do its job because of the help of international partners. Thanks for joining us from another edition of Behind the Web. 

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