When the US, Europe, and Canada first unveiled the plans for the James Webb Space Telescope in 1997, it sounded like a pitch from an overambitious science student. The contraption would have to schlep a 26-foot-wide mirror across the solar system, while keeping its cool around the radioactive sun. But to build the Next Generation Space Telescope (as it was called at the time), astronomers had to think big. Hubble, the preeminent space telescope, needed a successor—and there were too many open questions about the Big Bang and the expanding universe.

Twenty-four years later, the Webb telescope has smashed a number of records with its design, production, and assembly. Biggest telescope built for space? Check. Costliest tool made for stargazing? Check. Dozens of delays on the way to the launch pad? Check check check.

[Related: The James Webb telescope will soon be hunting for first light]

So it’s fair to say, the stakes are higher than imagined. As the world cautiously waits for the telescope to kick off its decade-long mission (the launch date is currently set for Christmas morning), here’s a look back on what it took to prepare it for this moment.

James Webb Space Telescope drawin in yellow and teal on a black background
An early concept for the James Webb Space Telescope—known at the time as the Next Generation Space Telescope—was designed by a Goddard Space Flight Center-led team. It already incorporated a segmented mirror, an “open” design, and a large deployable sunshield. In 1996, an 18-member committee led by astronomer Alan Dressler formally recommended that NASA develop a space telescope that would view the heavens in infrared light—the wavelength band that enables astronomers to see through dust and gas clouds and extends humanity’s vision farther out into space and back in time. NASA
James Webb Space Telescope 3D model against the Austin, Texas skyline
A full-scale model of the James Webb Space Telescope debuted for the first time in 2013 at the South by Southwest festival in Austin, Texas. Chris Gunn/NASA
Engineer in protective gear inspecting six of the James Webb Space Telescope's hexagonal gold-coated mirrors at a NASA testing facility
Ball Aerospace optical technician Scott Murray inspects the first gold primary mirror segment, a critical element of NASA’s James Webb Space Telescope, prior to cryogenic testing at the Marshall Space Flight Center in Huntsville, Alabama. David Higginbotham/NASA/MFSC
Gold insulation and black wire covering the James Webb Space Telescope's inner parts
What looks like a giant golden spider weaving a web of cables and cords, is actually ground support equipment, including the Optical Telescope Simulator (OSIM), for the James Webb Space Telescope. OSIM’s job is to generate a beam of light just like the one that the real telescope optics will feed into the actual flight instruments. This photo was taken from inside a large thermal-vacuum chamber called the Space Environment Simulator (SES), at the Goddard Space Flight Center in Greenbelt, Maryland. The golden-colored thermal blankets are made of aluminized Kapton, a polymer film that remains stable over a wide range of temperatures. The structure that looks like a silver and black cube underneath the “spider” is a set of cold panels that surround OSIM’s optics. Chris Gunn/NASA
Engineers in protective gear blasting one of the James Webb Space Telescope's gold-coated primary mirrors with white powder
Just like drivers sometimes use snow to clean their car mirrors in winter, two Exelis Inc. engineers are practicing “snow cleaning'” on a test telescope mirror for the James Webb Space Telescope at NASA’s Goddard Space Flight Center. By shooting carbon dioxide snow at the surface, engineers are able to clean large telescope mirrors without scratching them. This technique was only used if the James Webb Space Telescope’s mirror was contaminated during integration and testing. Chris Gunn/NASA
Two NASA engineers in protective clothing looking at micro sensors from the James Webb Space Telescope under a white light
NASA engineers inspect a new piece of technology developed for the James Webb Space Telescope, the micro shutter array, with a low light test at NASA’s Goddard Space Flight Center. Developed at Goddard to allow Webb’s Near Infrared Spectrograph to obtain spectra of more than 100 objects in the universe simultaneously, the micro shutter array uses thousands of tiny shutters to capture spectra from selected objects of interest in space and block out light from all other sources. Laura Baetz/NASA’s Goddard Space Flight Center
NASA engineer standing in a tunnel holding six of the James Webb Telescope's hexagonal primary mirrors in the honeycomb formation
NASA engineer Ernie Wright looks on as the first six flight-ready James Webb Space Telescope’s primary mirror segments are prepped to begin final cryogenic testing at the Marshall Space Flight Center. This represents the first six of 18 segments that will form NASA’s James Webb Space Telescope’s primary mirror for space observations. David Higginbotham/NASA/MFSC
NASA engineer in protective gear places a contamination panel on a James Webb Space Telescope part in a gas chamber
Contamination from organic molecules can harm delicate instruments and engineers are taking special care at NASA to prevent that from affecting the James Webb Space Telescope (and all satellites and instruments). Nithin Abraham, a thermal coatings engineer, places Molecular Adsorber Coating or “MAC” panels in the giant chamber where the Webb telescope was tested. This contamination can occur through a process when a vapor or odor is emitted by a substance. This is called “outgassing.” The “new car smell” is an example of that, and is unhealthy for people and sensitive satellite instruments. Christ Gunn/NASA
Metal backbone of James Webb Space Telescope with a single gold mirror inserted
A bird’s-eye view of NASA Goddard’s cleanroom and the James Webb Space Telescope’s test backplane and mirrors sitting in their packing case. Chris Gunn/NASA
James Webb Space Telescope primary mirrors on a giant trolley in front of a vacuum chamber at the Johnson Space Center
The James Webb Space Telescope emerges from Chamber A at the Johnson Space Center in Houston on December 1, 2017. The telescope’s combined science instruments and optical element exited the massive thermal vacuum testing chamber after about 100 days of cryogenic testing inside it. Scientists and engineers at Johnson put Webb through a series of tests designed to ensure the telescope functioned as expected in an extremely cold, airless environment akin to that of space. Chris Gunn/NASA
James Webb Space Telescope mirrors with sunshield attached at bottom
The Kapton® polymer-coated membranes of Webb’s sunshield were fully deployed and tensioned in December at Northrop Grumman in Redondo Beach, California. Northrop Grumman designed the observatory’s sunshield for NASA. During testing, engineers sent a series of commands to spacecraft hardware that activated 139 actuators, eight motors, and thousands of other components to unfold and stretch the five membranes of the sunshield into its final taut shape. A challenging part of the test is to unfold the sunshield in Earth’s gravity environment, which causes friction, unlike unfolding material in space without the effects of gravity. For launch the sunshield will be folded up around two sides of the observatory and placed in an Ariane 5 launch vehicle, which is provided by the European Space Agency. Chris Gunn/NASA
James Webb Space Telescope between two cranes in a warehouse
Reaching a major milestone, technicians and engineers successfully connected the two halves of the James Webb Space Telescope for the first time at Northrop Grumman’s facilities in Redondo Beach, California. To combine both halves of Webb, engineers carefully lifted the telescope (which includes the mirrors and science instruments) above the already-combined sunshield and spacecraft using a crane. Team members slowly guided the telescope into place, ensuring that all primary points of contact were perfectly aligned and seated properly. Next the team would have to electrically connect the halves, and then test the electrical connections. Chris Gunn/NASA
A team of NASA engineers in protective clothing lifting the Kapton insulation on the sunshield on a long runway
Technicians and engineers working to ensure the soundness of the James Webb Space Telescope by manually lower its folded sunshield layers for easier access and inspection. After being lowered, engineers thoroughly inspect all five layers of the reflective silver-colored sunshield for any issues that may have occurred as a result of acoustic testing. Acoustic testing exposes the spacecraft to similar forces and stress experienced during liftoff, allowing engineers to better prepare it for the rigors of spaceflight. Chris Gunn/NASA
The cargo ship that transported the James Webb Space Telescope against palm trees in French Guiana
The arrival of the James Webb Space Telescope to Port de Pariacabo in French Guiana on October 12, 2021. It traveled from California, through the Panama Canal, aboard the MN Colibri. 2021 ESA-CNES-Arianespace/Optique vidéo du CSG – JM Guillon
Ariane 5 rocket with purple boosters being prepared at the spaceport for the James Webb Space Telescope launch
The Ariane 5 core stage is 5.4 meters in diameter and 30.5 meters high. At launch it will contain 175 tons of liquid oxygen and liquid hydrogen propellants. With its Vulcain 2 engine it provides 140 tons of thrust. It also provides roll control during the main propulsion phase. This rolling maneuver will ensure that all parts of the payload are equally exposed to the sun which will avoid overheating of any elements of the James Webb Space Telescope. Chris Gunn/NASA
James Webb Space Telescope folded up in a cylinder on a vertical platform surrounded by a plastic cover
The James Webb Space Telescope atop its launch vehicle, before it was encapsulated in the rocket fairing. A protective clean tent was placed around the telescope until launch time. Chris Gunn/NASA