GUEST BLOG / Analysis by BBC Science Editor, Rebecca Morelle--Expectations are now sky high. It's time for astronomers to breathe a sigh of relief. Usually, it's the launch that's the most nail-biting part of a mission but the last two weeks have been even more nerve-wracking.
Unfolding a telescope of such colossal proportions has been one of the most challenging deployments ever attempted in space. But team Webb has done it. And, in fact, it's gone so smoothly, they've made the task look easy.
The decades of work on the telescope's design and its innovative engineering have clearly paid off. The real proof of the observatory's power though won't come until this summer when the first images are captured and beamed back to Earth. And expectations are sky-high - the views should not only be spectacular but they could also answer some of the biggest questions - like how did our Universe begin and does life exist beyond the Earth? Webb has a lot of promise to live up to.
There is still much to do to get James Webb ready to image the Universe. The initial task is simply to let it get very cold. The telescope is designed to work in the infrared. It's at this longer wavelength of light (longer than we can see with our eyes) that the pioneer stars will be observed to shine.
But unless Webb is taken down to a super-low temperature, its own heat energy will swamp the faintest of signals. "We'd be blotting out the very thing we want to see; it would be like trying to look at a lighted match in front of a burning haystack. You'd be lost," said Gillian Wright one of Webb's principal investigators. The big shield will produce a shadow from the Sun that will eventually put Webb below -230C.
Only in this frigid condition will the four scientific instruments onboard have the required sensitivity. Engineers will begin checking over their function and performance shortly. They'll also have to align all 18 hexagonal segments in the main mirror to make them behave like a single monolithic reflecting surface. Each of the segments has motors at the rear that can move them up and down, tip them sideways, rotate them, and even slightly bend them to give them exactly the right curvature.
All of this preparatory work will fill the next five months or so. The first public release of pictures from Webb is not expected until the end of June at the earliest. But we should be prepared to be wowed, say space agency officials. "Webb is an engineering marvel, but it also has this beauty to it," enthused Lee Feinberg. "One of my favourite things was to watch people's faces when they walked up and looked at it. There is a feeling of awe that humans created this thing. It's just the size and the scale, and the gold coatings. It really lifts you up," he told BBC News.