It is the size of a tennis court and next year it will go into orbit as part of the most sophisticated space telescope ever built.
The kite-shaped object is a mask that will protect the James Webb observatory from the glare and heat of the Sun as it tries to image the deep Universe.
Engineers have just finished joining together its individual layers.
These membranes, made from a polymer material known as kapton, are as thin as a human hair.
In their shade, the Webb telescope should be able to reach its operating temperature of less than 50 degrees above absolute zero (-223C).
The finished shield is too big to fit in a rocket, however - as is the James Webb telescope.
Observatory and shield must therefore be folded up on themselves, origami style, for the ride to orbit. Only when they get into space can they be unpacked into an operational configuration.
The Northrop Grumman Corporation in Redondo Beach, California, which leads the industrial consortium on the project, is currently packing and stowing the membranes ahead of deployment tests that will take place later this month.
Assuming all goes to plan, the shield will then be attached to Webb's foldable mirrors and instruments.
These elements are due to arrive at Redondo Beach later in the year.
They are presently in tests of their own at the US space agency's Johnson centre in Texas. These investigations aim to ensure the telescope can focus and analyse light properly.
James Webb is often described as the successor to the Hubble Space Telescope which is nearing the end of its mission life.
The obvious difference is that Webb is much bigger. Its main mirror is 6.5m across versus Hubble's 2.3m. But the new observatory will also be working at longer wavelengths of light compared with its predecessor.
Webb will sense in the near and mid-infrared range of the electromagnetic spectrum. This should allow the telescope to look deeper into space than Hubble, to see the very first stars to ignite in the cosmos more than 13 billion years ago.
The James Webb Space Telescope is a joint endeavour of Nasa, and the European and Canadian space agencies. Its launch on a European Ariane rocket is currently scheduled for October 2018.