In a cavernous, dust-free workroom at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, engineers and technicians are putting the finishing touches on one of the most ambitious telescopes ever built.

When it’s launched in 2018, the James Webb Space Telescope will enable scientists to peer into the oldest, farthest reaches of the universe and search for signs of life on distant planets.

“We want to see the first stars and understand how stars, galaxies and planetary systems are formed,” John Durning, deputy project manager for the Webb, said at Goddard recently while technicians worked inside the center’s 10-story “clean room.”

“We don’t understand how we got here,” he added, “and we need to go to the beginning to figure that out.”

Scientists theorize that the universe began with what is known as the big bang about 13.8 billion years ago and that the first stars formed 400 million years later. To see those stars, the Webb will use special instruments to study an invisible form of light that is given off by all objects, especially hot ones.

An artist's illustration of the James Webb Space Telescope, which will launch in 2018. The kite-shaped object beneath the telescope's mirror is its sun shield, which protects the Webb’s instruments from the sun’s heat. (Northrop Grumman)

Looking at that infrared light will allow the unmanned telescope to pull back the curtains of the universe and see stars too distant even for the Hubble, the Webb’s powerful predecessor.

The $8.7 billion Webb project, named for a NASA administrator who helped launch the Apollo moon program in the 1960s, began 20 years ago as a collaboration between NASA and the European and Canadian space agencies. The telescope is designed to work for at least five years and has enough fuel to operate for a decade.

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Central to its design is a set of 18 gold-coated mirrors that are sensitive enough to reflect the light of a single match struck on the moon. The light is analyzed and recorded by instruments that are protected from the sun’s rays by an umbrella as large as a tennis court.

Known as a sun shield, the paper-thin layer of plastic keeps the instruments as cool as 400 degrees below zero. “In terms of sunscreen,” Durning said, “the shield has an SPF of about 1 million.”

And just like an umbrella or a Transformer robot, the sun shield — and the rest of the telescope — folds up, allowing the 15,000-pound Webb to fit snugly inside a rocket.

Once the Webb is launched, it will take about two weeks for the telescope to unfurl and another two weeks for it to begin orbiting the sun — at a point in space that is a million miles from Earth. By comparison, the Hubble is orbiting about 340 miles from Earth.

The Webb still needs to undergo final tests and additions. It will be flown to Houston, Texas, in March and eventually shipped to South America for launch from French Guiana.

Technician Marc Sansebastian will be there to make sure nothing goes wrong. He recently spent four hours inside the telescope, painstakingly applying a small device that will measure the Webb’s movements during a motion test.

He said that working on something that has cost billions of dollars and years of effort is a little bit stressful, but also exciting. With a tool in hand, he said, stepping inside the Webb is like playing “the ultimate game of Operation.”