CAPE CANAVERAL: The US space agency (Nasa) aced the most complicated, critical job on its newly launched space telescope on Tuesday: unrolling and stretching a sunshade the size of a tennis court.

Ground controllers cheered and bumped fists once the fifth and final layer of the sunshield was tightly secured around the James Webb telescope. It took just 36 hours to tighten the ultra-thin layers using motor-driven cables, half the expected time.

The seven-ton telescope is so big that the sun-shield and the primary gold-plated mirror had to be folded for launch. The sun shield is so unwieldy that it spans 70 feet by 46 feet to keep all the infrared, heat-sensing science instruments in constant subzero shadow.

The $10 billion telescopes are more than halfway toward its destination 1.6 million kilometers away, following its Christmas Day sendoff. It is the biggest and most powerful observatory ever launched — 100 times more powerful than the Hubble telescope — enabling it to peer back to almost the beginning of time.

Considered Hubble’s successor, Webb will attempt to hunt downlight from the universe’s first stars and galaxies. “This is a really big moment,” project manager Bill Ochs told the control team in Baltimore. “We’ve still got a lot of work to do, but getting the sun shield out and deployed is really, really big.”

Engineers spent years redoing and tweaking the shade. At one point, dozens of fasteners fell off during a vibration test.