The $10 billion James Webb Space Telescope has completed its insertion burn at the second Lagrange (L2) point a million miles, or 1.5 million kilometers, from Earth, successfully completing its 30-day deployment.
Webb will now sustain what is known as a halo orbit around L2 for at least the next 10 years, where it will use its infrared detectors to look deep into the universe's past to the earliest stars and galaxies to form after the Big Bang.
Stars and galaxies from the earliest days of the universe, the first ever to form after the Big Bang, have had their light stretched by the expansion of the universe to such a degree that the light they emitted more than 13 billion years ago has been pushed out of the visible spectrum by a process known as red-shifting.
This turns visible light into infrared light that it is no longer detectable by normal telescopes. The deep-infrared sensors on Webb therefore aim to do what no other telescope ever made can do and capture that light for the first time.
The first images from Webb are expected in late April at the earliest (though late May is more likely), after Webb's sensors have had sufficient time to cool down to -369.4 degrees Fahrenheit/-223 degrees Celsius–which is the temperature cold enough to capture some of the faintest infrared light possible without having to worry about interference from the heat of the Sun or even Webb's own instruments–and its 18 primary mirror segments have been aligned to within 10s of nanometers.
For now though, NASA and all of the various engineers from around the world, both government and private contractors, are celebrating what is unquestionably one of the greatest engineering achievements of all time.
Analysis: this is an incredible human accomplishment
To say that this is a big deal for astronomers is a gross understatement.
Webb is the most advanced telescope ever deployed, and its sophistication means that it is also incredibly complex as far as space telescopes go.
From its iconic honeycomb primary mirrors to its secondary mirror at the end of a set of extended mechanical arms to the five sheets of delicate Kapton that make up its tennis court-sized sunshield, there were literally hundreds of points of failure during Webb's deployment.
Everything needed to go right in order for Webb's deployment to be successful, and at every step of the way, human ingenuity succeeded in accomplishing the extraordinary.
The final test will be when the first images from Webb come in after the telescope has had time to cool down to its operating temperature, which is just 50 degrees Celsius higher than the coldest temperature physically possible.
If everything works as it was designed, we will see sights in the universe we have literally never seen before, looking back through time to more than 13 billion years ago when the very first stars formed after the birth of the universe itself.
It wasn't until Hubble took its first images, though, that we learned that its mirror had been incorrectly machined and had to be replaced. Should something like that happen with Webb, there will be nothing we can do about it.
It might not lead to a complete failure of the telescope (that possibility is genuinely remote at this point), but those first images will show whether we slightly missed the mark, or whether this intense, two-decade-long international scientific effort was executed flawlessly.
Conrad Wells, a Senior Optical Systems Engineer at L3Harris who was a lead engineer on Webb's main optical telescope element, isn't worried. Wells and the L3Harris engineers have done extensive testing so that there won't be any surprises the way there were with Hubble's deployment, including a full system test from end to end to make sure that the optical systems work exactly as they should.
"All of us have a high degree of confidence that the optical system is going to work well," Wells told TechRadar as Webb completed its historic deployment. "This is the second time that we’ve done it, it’s not the first time. NASA’s insistence, and our execution of that system level test, is going to make this mission a success.
"It's going to work."
The effort to deploy Webb was unprecedented and has been executed flawlessly, which is reason enough to celebrate. Now we wait. The next five months can't pass fast enough.