NASA's James Webb Space Telescope launches: 'Milestone achieved'

This outstanding, meticulously crafted and trailblazing piece of machinery is now on its way to show us the first light in the universe -- from 13.7 billion years ago. We'll start hearing back from Webb six months from now.

"Milestone achieved," says NASA.

Arguably the most crucial part of today's launch is a success! Webb's solar panels have deployed and it's charging up for the cosmic adventure of a lifetime.

Amid applause, the upper stage camera offers us the very first views of Webb, and soon after, our very last views as the telescope moves toward its work station.

Main engines are off "exactly as expected" and Webb is in its coasting phase. The telescope will be separated from the upper stage of the Ariane 5 in just a few seconds, readying itself for the risky unfurling procedures.

After Webb's thrusters are working, its solar arrays are scheduled to be deployed at the 30 minute mark post-launch.

"Within the first day, we expect to get signals back that it has deployed the solar panels and that it is power positive," according to Webb engineer Alison Nordt, the space science and instrumentation director at aerospace giant Lockheed Martin.

Once that's done, ground control will be waiting for its very first communication with Webb.

The main engine has been cut off, leading to the next phase of the sequence -- separation. 

Everything's still looking nominal and the section of the rocket containing Webb is now traveling alone at 220 kilometers in altitude and a bit over 7 kilometers per second.

The vehicle performance and trajectory is reported as "nominal." The trajectory appears to be as expected and ground control is waiting for the next separation.

Webb's right up there, experiencing its last days on Earth in the tip of the Ariane 5 rocket. "Weather is go, green board, no issues." The last minute before countdown is getting closer.

It's a relief, Webb is going to launch in about 7 minutes -- confirmed, at last. 

We're seconds away from entering the critical synchronized sequence where you'll hear everyone calling for every final check on the scope.

"Don't let those clouds fool you." All weather parameters are still green and Webb's launch is still on for 4:20 a.m. PT. The most critical phase of the countdown will soon begin. 

We'll very, very soon have the final weather report to ensure absolutely no. more. delays.

All fueled up as of just over 30 minutes ago, and the green light is still lighting the way for Webb to change our understanding of the universe! 20 minutes left till launch.

At liftoff, we'll see the main engine ignite before boosters are switched on to make sure it's working. So, don't be surprised if you're seeing Webb turn on and not move. But after the boosters are on, "there's no turning back, the rocket is going to lift off."

"Yes, they're starting," Greg Robinson, the James Webb Space Telescope program director says of the butterflies everyone's been asking about. And 20 minutes prior to launch, they'll really start to fly, he says.

30 minutes until the launch window opens for Webb. I hope you're all as caffeinated and pumped as I am. 

According to NASA, 4:52 a.m. PT will be the latter end of the launch window.

Over at mission control, engineers are "laser focused" on the last checks for Webb as we approach the opening of the launch window at 4:20 a.m. PT.

Webb is still ready with a green light. 10 minutes before launch, though, we'll get a final update on if we're still a GO on the note of weather.

In the event of a successful launch, experts say it'll take about six months for ground control to receive the very first images from Webb. That's after the telescope is completely unfurled from its origami-like folds, safe from heat from the sun (to ensure NIRCam and other infrared imaging processors work) and orbiting at the second Lagrange point around the sun. 

Yep, Webb won't be orbiting Earth. It'll be orbiting the sun.

All positions have reported they are GO for the final phase of the countdown. Fueling of the Ariane 5 rocket began before sunrise, and mission control in Kourou, French Guiana says there are "no issues" for the launch pattern to commence on time this Christmas day.

Construction began on Webb in 2004, nearly 20 years ago. After a long ride, it's been armed with a few crucial tools that set it apart from Hubble, such as NIRCam, a gold-plated, 18 segmented mirror and heavily layered sunshield. 

There's a lot going on in the nose of that Ariane 5 rocket you're seeing. After launch, every bit of Webb must flawlessly unfold, making today's occasion the start of one of NASA's most complex liftoff sequences yet.

John Mather, senior project scientist for the James Webb Space Telescope, discusses some of the spectacular implications Webb can have. 

The space probe can help us understand how planets and stars formed just after the Big Bang, study the composition of exoplanets and so much more. We've heard that humans are made of stardust, but...how? Eventually, Webb's data can touch on some answers.

The James Webb Space Telescope is successfully on the pad, just under 1 hour before the launch window opens. Right now, the vehicle is being topped up with NASA's "game changing" cryogenic fuel.

Weather's looking great, it's bright and early on Christmas morning, the scope is officially set for launch.