The JWST has now reached L2, the location where it will show us the universe.
It's been one hell of a journey, marked by a dozen delays before it even reached the launch pad. Unfortunately, we still have months to wait before being dazzled by the first images of the first stars and nearby exoplanets the telescope will send back, as careful adjustments of the mirror alignments are still underway.
L2 (technically Sun-Earth Lagrangian Point 2) is one of five locations where the gravitational forces of the Earth and Sun cancel out the force of a satellite's motion, creating a stable location relative to the Earth.
For a telescope like the JWST, being near L2 has the advantage of having the Sum, Earth, and Moon all in one direction, ensuring the shields only need to point one way to keep out their radiation.
Technically, rather than operating precisely in L2, the JWST will orbit around it, which is actually an easier orbit to maintain. Although the orbit around L2 does not face the same dangers of overcrowding as low-Earth orbit (at least not yet) the JWST will have some company there in the form of existing or former WMAP, Herschel, and Planck space telescopes.
Overshooting even slightly would have been disastrous, so NASA engineers never planned to put the JWST around L2 in a single step. Instead, the idea was to get it into a lower orbit where its sun-shields and mirrors could open safely, before giving the final nudge.
The extra fuel burn added just 1.6 meters per second (5.8 kilometers per hour or 3.6 miles per hour), a typical walking speed, to its orbital velocity – but this was enough to boost it to a distance of almost a million miles (1.5 million km) from Earth and to orbit the Sun, not the Earth.
The process was designed to use as little propellant as possible, as every bit left over leaves more to be used for the corrections that will occasionally be necessary to balance radiation pressure from the Sun. An exceptionally efficient launch used less propellant than anticipated, doubling the JWST's anticipated operating lifespan.
“Webb, welcome home!” NASA Administrator Bill Nelson said in a statement. “Congratulations to the team for all of their hard work ensuring Webb’s safe arrival at L2 today. We’re one step closer to uncovering the mysteries of the universe. And I can’t wait to see Webb’s first new views of the universe this summer!”
Or, as one of the JWST parody Twitter accounts put it: