[MUSIC PLAYING] We are here at the Marshall Space Flight Center in Huntsville, Alabama, known for its long history in propulsion research. But this NASA site is still a big player, this time for the James Webb Space Telescope. We're right outside the vacuum chamber where the mirrors for the Webb Space Telescope are being tested. Back in the '90s, this facility was used to test out one of NASA's great observatories, the Chandra X-ray Observatory. We have here the project scientist for Chandra, Martin Weisskopf. Can you tell us a little bit about the differences between Hubble, and Chandra, and James Webb? 

These are observatories that look at different parts of what we call the electromagnetic spectrum. That is light at various different energies, from x-rays where it takes a lot of energy to produce them, to visible light where the Hubble Space Telescope operates, and the near infrared where the James Webb Telescope will operate. In this way, by studying objects in the universe, we can learn a lot about them that we can't learn by just simply looking at one wavelength. 

What kind of information can we glean from x-rays? 

X-ray astronomy is the system that brought the first discoveries of black holes in the universe. So we look at very interesting astronomical objects at very great distances. In conjunction with Hubble, Webb will be looking to identify many Chandra sources that are not seen with Hubble. 

Now we're outside the facility where the mirror testing is being done. And you can't help but see this long tube that is connected to the building itself. I'm told it's almost six football fields long. Martin, what was this tube used for? 

This tube is very important for separating the telescope that was on the Chandra X-ray Observatory from x-ray sources located at the other end of the building. It has to be this length in order to make those x-ray sources appear like tiny stars so that we could determine whether our x-ray telescope could distinguish small objects in the sky. 

Why is it still here? Chandra was tested in the mid-'90s. 

It's still here because it's very, very useful for many programs. The vacuum chamber is being used to test the Webb optics. And we hope to be testing x-ray telescopes in future programs. 

Well, thanks for your time, Martin. 

You're quite welcome. 

The testing here for the Chandra Observatory ran about six months, from 1996 to 1997. Then the telescope was sent off to be integrated with the rest of the observatory. Chandra was launched on July 23, 1999. Thanks for joining us for another edition of Behind the Web. 

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