The Hubble Space Telescope is 17 years old — that’s like 150 to you and me. Next year, the geriatric orbiting eye will receive its final tune-up, and soon it will go live on a farm where it can play with other obsolete space-based observatories. The good news is that NASA scientists have already cooked up a replacement. The James Webb Space Telescope, scheduled for a 2013 launch, folds to fit into the cone of a rocket for deeper deployment than its predecessor. Once in orbit, it will capture infrared instead of visible light and — since distance equals time in space — will be able to see back to about 400 million years after the big bang. That should let it snag shots of the first bright objects, the origins of planetary systems, and the assembly of galaxies. “Every time you get new capabilities, you see a quantum jump in progress,” says Mark Clampin, the observatory’s project scientist. “I’m sure we’ll discover things we’ve never seen before.”
The New Space Telescope, Unfolded
Hubble’s reflectors are too small to probe the farthest galaxies. So the Webb is equipped with 18 hexagonal beryllium mirrors, each 51 inches wide. Beryllium is lighter, stronger, and more stable then glass — the completed array will be half the weight of Hubble’s main mirror but 2.5 times bigger. Each segment can pivot in six different directions and can be adjusted from Earth.
2 Micro shutters
The business end of the telescope (the collector) has 62,415 openings, measuring about 100 x 200 microns each. These can capture spectrographs — images of incoming electro magnetic radiation — from 100 galaxies at a time. Scientists will be able to open and close the shutters separately, depending on which gal axies are in the Webb’s field of view.
3 Infrared devices
The new telescope features four high-pixel density image sensor arrays — not so different from the ones found at the heart of a typical digicam. In this case, there’s a near-infrared camera, a near- infrared spectrograph, a mid-infrared camera, and a fine guidance sensor.
4 Sun shield
The sun’s heat can easily overwhelm the infrared light that the telescope is looking for. Solution: five tennis-court-sized Mylar shields. Coated in aluminum and conductive silicon, the parasols will keep the scope cold enough to capture images while protecting it from radiation. Why five layers? Micrometeoroids! More layers means the slow buildup of small holes won’t have an effect.
Earth is a crummy vantage point for looking at space — a hazy atmosphere prevents detection of some wave lengths, heat screws up infrared imaging, and atmospheric turbulence distorts focus. To avoid all this, scientists will shoot the Webb telescope to what is known as Lagrange point 2, a spot 932,000 miles out that’s balanced between the gravities of Earth and the sun.
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