NASA Installs a Heat Shield the Size of a Tennis Court to Its Latest Telescope

Engineers have packed a huge heat shield onto the James Webb Telescope to prepare it for its launch later this year.

Like the Hubble Space Telescope, Webb will be placed in space so that it can take photos of the cosmos without having to peer through the Earth's atmosphere first.

But while Hubble orbits the Earth at a distance of around 347 miles, Webb will orbit our sun, and be around a million miles away from us.

It will need a heat shield to protect it from the glare of our nearest star, so engineers have designed the shield to guard the telescope's delicate optics.

In addition, Webb is an infrared telescope, which means it is sensitive to extremely faint heat signals from objects potentially billions of light-years away. The mirrors and sensors must be kept extremely cold; another crucial task for the heat shield.

To keep the telescope cold, one side of the shield will constantly be facing the Sun and the other will always be facing away. The hot side will deal with temperatures as high as 230 degrees F, while the cold side will be at around -394 F.

The shield is also large at 70 feet by 47 feet—about the same size as a tennis court. It has to be precisely folded for it all to fit inside the 18-foot diameter payload section of the Ariane 5 rocket that will launch it into space, where it will unfurl.

Folding the sunshield took a month, and the five layers that it consists of are extremely thin; four of them are just 0.001 centimeters thick.

At the end of Webb's first week in space, the shield needs to re-open in exactly the right way. Some 107 pins will have to release in order for this to happen, and there are also 90 different tensioning cables.

Jeff Cheezum, a lead sunshield engineer at aerospace and defense firm Northrop Grumman, said in a statement: "Just like a skydiver needs their parachute packed correctly in order to open perfectly and to successfully get back to Earth, Webb needs its sunshield to be perfectly stowed to ensure that it also opens up perfectly and maintains its shape, in order to successfully keep the telescope at its required operating temperature."

Engineers will now spend three months stowing the packed sunshield away before launch. In July last year, NASA said it was targeting an October 31, 2021 launch date. Webb will lift off from French Guiana.

The James Webb Telescope will look at galaxies that are over 13 billion light-years away from Earth. To capture their faint infrared radiation, it needs a huge mirror. At 21 feet 4 inches across, it is the largest ever launched into space.

For comparison, the Hubble Space Telescope's primary mirror is 7 feet, 10.5 inches across.

James Webb heat shield
In this photo, engineers and scientists examine the sunshield layers back in 2014. NASA, Northrop Grumman, and NeXolve Corporation are all involved in the shield. Alex Evers/Northrop Grumman