What do you do when your cutting-edge space telescope turns out to be too big for any rocket available? If you’re NASA, and the instrument in question is the James Webb Space Telescope, you make it into a masterpiece of tech origami so that it can fold like a butterfly into the Ariane 5 rocket scheduled to take it into orbit.
It’s the largest and most complex space telescope developed so-far, and when opened up its vast sunshield will measure more than 66 feet by 46 feet. NASA finished assembling it in August 2019, and since then has been doing testing on the mirrors and science instruments.
Webb actually consists of two main parts. On the one hand there’s the telescope itself, which is a conical assembly that can be pointed at distant galaxies. Its Optical Telescope Element consists of eighteen 52-inch hexagonal mirror segments, each made of beryllium and plated with gold. They combine to form a 21 foot diameter mirror, significantly larger than that of the Hubble Space Telescope.
For it to properly observe the infrared spectrum, however, it needs to be kept cool. That’s where the second part comes in, the huge sunshield that will help keep it below -370 degrees Fahrenheit. Its five layers are each as thin as a human hair, and are made from polyamide film with coatings of aluminum and silicon.
To squeeze into the Ariane 5 rocket, the sunshield will have to fold twelve times in total. That will bring the Webb telescope down to something that fits in the 15 foot by 53 foot payload fairing, like a moth in a chrysalis.
Next, with the telescope successfully collapsed down, the NASA, ESA, and Canadian Space Agency engineers can do their final acoustic and vibration testing. Assuming it aces that, it will be deployed one last time before being dispatched to French Guiana for its launch in ten months time.
It’s not been an easy path to here. Engineers ran into issues with tears in the delicate sunshield, which delayed the project, and previous cost-overruns have made it controversial in political circles. Once in space, it will be positioned near the EarthSun L2 Lagrangian point, also assisting in keeping the instrumentation cold. Designed to last for five years, but with at least ten the goal, it will give astronomers unprecedented insight into the light of the first stars in the universe, formed after the Big Bang.
It’ll also study how galaxies form and evolve, as well as how stars and planetary systems are born and then die. The designers hope that its near-infrared sight will allow it to help identify the origins of life, and other planets where conditions might also be conducive to life forming. Still, it’s a risky project and the team on Earth need to get it absolutely right before Webb takes off. The telescope is not designed to be serviceable once in space and, unlike Hubble’s storied past, if something goes wrong the instrumentation cannot be repaired or replaced.