The James Webb Space Telescope is NASA's successor to Hubble. Mind you, it's not a replacement: JWST will see in the infrared, peering deeper into the Universe with its ginormous 6 meter unfoldable mirror than Hubble can.
But that infrared part is important. Objects that are warm give off IR light, and if you don't cool your telescope, it'll glow in the wavelengths you're trying to see. It would be like having a flashlight shining down your 'scope!
So JWST has to be cooled, and since it'll be in a spot in space where the Sun shines 24/7 (the so-called L2 point, where the Sun's and Earth's gravity balances), it basically needs a sunshade. And also since the 'scope is pretty big, the shade itself has to be sizable.
What engineers came up with is a multi-layered blanket of material that will sit "underneath" the telescope, blocking the sunlight and passively cooling the whole thing. The shade will be pretty big, about the size of a tennis court! To make sure it works, they created 1/3 scale model of the actual shade. This diminutive has been built, and is now undergoing tests at Goddard Space Flight Center.
[Click to deployenate]
Cool! Um. Literally.
You can also keep up with the construction of JWST using a webcam mounted in the clean room. I remember that room well; though I never got in I used to watch them work on Hubble cameras there.
Also, to give you an idea of just how big JWST will be... In 2007, I was at an astronomy meeting where a frakkin' full-scale JWST model made an appearance. Here's a video I made about it:
I did my best with this video considering the day before I was dying from a norovirus. Man, I love Seattle, but that was a rough week.
Anyway, JWST is still planning a 2014 launch. If you like Hubble images, JWST will blow you away. Just the galaxy shots it will produce will be spectacular beyond compare. And the deep field images will go much farther than Hubble can, if you can imagine that! JWST is a revolution in astronomy waiting to happen, every bit as much as Hubble was. Let's hope these tests go well, and we can get that bird flying.