In the February issue of Scientific American two astrophysicists offer a close-up look at a telescope they are developing for NASA. The Nuclear Spectroscopic Telescope Array (NuSTAR) is the space agency's first mission capable of focusing high-energy x-rays. Among other goals, NuSTAR is expected to capture the highest quality hard x-ray images to date of black holes, neutron stars and other extreme phenomena. The photo feature in the magazine showed just the optics; this slide show reveals NuSTAR's other components as they are assembled in preparation for the telescope's launch next year.

Slide Show: A Look inside NASA's Next X-Ray Observatory

8 Comments

1. 1. rushil2u 11:43 AM 1/26/11

   How precisely does one go about 'focusing' X-rays? I was under the impression that they are difficult to refract. And where does NuSTAR's elaborate arrangement of mirrors come into the picture?
   Anyone in the know out there, do enlighten me.

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2. 2. starsandspice 12:16 PM 1/26/11

   X-rays can be focused, but it's difficult. X-rays reflect (not refract) at what's called grazing incidence angles - i.e., *very* small angles. The higher the X-ray energy, the smaller the angle. That's why the mast of NuSTAR has to be so long, so that X-rays of very high energies (5-85 keV) have a long enough space to reflect and focus at the detector.

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3. 3. jtdwyer in reply to starsandspice 01:26 PM 1/26/11

   Very good question, rushil2u, and excellent explanation, starsandspice - thanks!
   
   So the x-rays focused in any single image must be within a very narrow window at a very specific distance - is that correct?

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4. 4. Wayne Williamson 05:35 PM 1/26/11

   Just wondering why they picked glass for the "focusing" mechanism...If I remember correctly...previous x-ray telescopes used stainless steel.....

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5. 5. Magellanic42 in reply to Wayne Williamson 11:06 AM 1/27/11

   XMM had aluminum shells, if I recall, and Chandra had 2mm glass. But where Chandra had 4 layers, NuSTAR has 133 in each optic. Also, each NuSTAR shell is 1/10th the thickness of a Chandra shell. They chose glass because it was lightweight, cheap and the easiest to shape.

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6. 6. girsperger in reply to rushil2u 10:26 AM 2/3/11

   You may find an in-depth explanation of NuSTAR's optics here: http://www.nustar.caltech.edu/about-nustar/instrumentation/optics

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7. 7. DaleW 06:44 PM 4/17/11

   The details of X-ray optics were given in the Sci Am article about the Uhuru satellite in the late 60s or early 70s. Sad to see that this article wasn't nearly as thorough, and also that the online archive doesn't go back nearly that far.
   
   But yes, it's very hard to refract X-rays, so the satellites use reflecting optics. The problem with that is that the fraction of X-rays reflected is small unless the angle of reflection is very small. It sounds like they use multiple, concentric mirrors, and each mirror has a layered reflective coating.
   
   I'd have liked to see more detail on how they get all the mirrors to reflect coherently, the detector system, and how the deployable mast system achieves accurate enough alignment. For that matter, the sizes of the components aren't even discussed in the article!
   

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8. 8. DaleW 06:47 PM 4/17/11

   I might be wrong above, the first X-ray focusing optics may have been on the Einstein satellite.

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