The world's biggest telescope under assembly, NASA's James Webb Telescope set for launch in 2018, has achieved a benchmark: the telescope part is now ready and all the sunshield layers are in place.

The last layer was received on Sept. 29 at the Northrop Grumman Corporation's Space Park facility in Redondo Beach, California.

"The completed sunshield membranes are the culmination of years of collaborative effort by the NeXolve, Northrop Grumman, and NASA team," said James Cooper, Webb telescope sunshield manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

This next-generation space observatory is the successor to the Hubble Space Telescope and will be the most powerful space telescope ever built.

The sunshield and the rest of the spacecraft will later fold into an Ariane 5 rocket. Considered a major milestone in the spacecraft's development, spanning 20 years, the telescope assembly has been progressing at Goddard Space Flight Center.

The James Webb Telescope is a joint venture of NASA, the European Space Agency, and the Canadian Space Agency.

Sensitive Sunshield

The sunshield is crucial in blocking the background heat from entering the infrared sensors of the telescope. Manufactured by the NeXolve Corporation in Huntsville, Alabama, the membrane is as thin as a human hair. The shield comprises 18 hexagonal mirrors, made of lightweight beryllium with gold coating.

Each layer of the sunshield is made of Kapton and stays cooler than the one beneath. According to NASA experts, the membranes can slash the temperatures between the hot and cold sides of the observatory by 570 degrees Fahrenheit.

In terms of size, each sunshield of the JWST will be the equivalent of a tennis court and make the mission of the telescope effective in imaging stars and galaxies created 13.5 billion years ago.

According to NASA, the shields will safeguard the optics and instruments of the telescope.

"Today we're celebrating the fact that our telescope is finished, and we're about to prove that it works," said John Mather, a JWST senior project scientist.

Northrop Grumman, which designed the telescope's optics and spacecraft, will integrate the final flight layers into the sunshield subsystem for the final validation process.

JWST Infrared Advantage

Meanwhile, experts say the main advantage of JWST will be its ability to pierce through cosmic dust to reveal the universe's first galaxies for discovering new planetary systems and collect infrared light, which the Hubble was unable to do.

With Earth's atmosphere glowing in the infrared light, it has been hard to make measurements from the ground as the Hubble also emits extra heat and mars the process of documenting infrared readings.

However, the JWST with its ability to work at absolute zero temperature can station at a point, Lagrange Point 2, behind Earth and shield itself from infrared emissions.