Just last week, NASA announced the alien-hunting James Webb Space Telescope had passed its latest round of cryogenic testing. Subjected to temperatures approaching absolute zero, this begs the question: Just how hardy does this mammoth telescope need to be?
A glimpse into the origins of the universe
Back on track after a series of delays, astronomers hope the telescope will answer some of the greatest mysteries of the universe. Often considered a successor to Hubble, it could pick up the first light of the Big Bang and the formation of the first galaxies. For alien-hunters, it will chart the atmospheres of distant exoplanets, helping scientists to gauge if they can support life.
A violent launch
The telescope will endure an incredibly violent launch, tearing through the Earth’s atmosphere to reach the depths of space. Engineers have used powerful vibration tests to measure how the technology should cope under this extreme motion, Geithner said.
Engineers used a giant electromagnetic-powered metal plate to shake the telescope up to 100 times per second. To test its endurance even further, they locked the equipment in an “acoustics chamber.” Geithner said: “This is a thick-walled room with large speakers that produce literally deafening levels of sound.”
“For a one-of-a-kind article like Webb, the levels of vibration we subject it to in testing on the ground is about twice what it will endure during the mission,” Geithner added.
Webb will face extreme temperatures in space. Leftover radiation from the Big Bang keeps space at an icy minus 455 degrees Fahrenheit, while intense heat blasting from the Sun fries everything in its path. An astronaut on a spacewalk within the Earth’s orbit would face temperatures between 250 and minus 250 degrees Fahrenheit.
The telescope will have to withstand both the cold and the heat for up to 10 years. Geithner described the engineering challenge this presents: “Webb has to survive the stresses of shrinking and expanding during cold temperature tests and warming it back up again—things that will happen when it goes into space.”
To test that Webb’s materials will adapt to these pressures without warping out of shape, NASA used cryogenic testing. This means putting the telescope into a giant freezer.
“We put the Webb telescope's hardware into a big vacuum chamber, close the door, pump all the air out, and then run liquid nitrogen and extremely cold helium gas through plumbing that crisscrosses the surface of thin “shells” that are nested Russian-doll style inside the vacuum chamber,” Geithner said.
The hot rays of the sun present an extra challenge for the Webb telescope, which sees using infrared light.
Geithner said: “For an infrared telescope to be as sensitive as possible, its optics and scientific instruments need to be very cold, so their own heat does not blind them to the faint infrared signals they are trying to observe from astronomical objects.”
To keep the instruments extremely cold, they will be shrouded in five layers of special plastic the size of a tennis court. “Basically, it looks like a five-layered, giant silver kite in space,” Geithner said.
The “belching” sun
Webb will sit outside of the Earth’s magnetic field, making it vulnerable to a constant barrage of subatomic particles from the sun.
“Earth’s magnetic field acts like a deflector shield for protons and electrons spewing all the time from the sun,” Geithner said. “These charged particles are hard on electronics.”
The sun will sometimes “belch” particles in the form of solar flares, where years’ worth of protons and electrons are ejected over just a few hours. Webb’s electronics are encased in metal boxes to give added protection from these events.
The telescope is designed to survive without maintenance for up to 10 years. If something does break, Webb can only be serviced by robots. Too cold for humans, only machines could conceivably repair and refuel the device.
Currently scheduled for launch between March and June 2019, the telescope could be as influential as the Hubble Telescope. Whether it will reveal the origins of the universe, capture the beginnings of our own galaxy or end the search for extraterrestrial life, we can only wait and see.
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