Engineers pose with NASA’s James Webb Space Telescope, or Webb, after it emerged from Chamber A at NASA’s Johnson Space Center in Houston, Texas, 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. 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. Photographer Chris Gunn: "All of NASA’s endeavors are group efforts and group photos are part of the NASA culture. This shot is probably one of the best group shots I’ve made including the telescope." #

The Optical Telescope Element (OTE) Simulator wrapped in a silver blanket on a platform, is lowered into a vacuum chamber called the Space Environment Simulator by a crane, to be tested to withstand the cold temperatures of space on March 30, 2012. Gunn: "This is a photograph of a piece of test equipment. There’s nothing in this shot that is flight. The community of Webb telescope watchers was eager for anything from the project so this shot was very popular." #

The amazing mirrors that will fly aboard the James Webb Space Telescope will allow it [to] see farther away and further back in time to detect the light from the very first and most distant stars and galaxies. In this November 6, 2012, photo, an engineer's crystal-clear reflection is seen on the surface of one of the primary mirror segments. The image is so clear you can see an expression of concentration in the engineer's face. Behind the engineer looking into the mirror's surface, the top part of the canister that the mirror was shipped in hangs from four straps. Other engineers use flashlights to inspect the mirror segment. Gunn: "The entire team was mesmerized. One of most interesting things about this image is that the bare ISIM (Integrated Science Instrument Module, the unit that will will house the four main instruments of Webb) structure sits in the background." #

A full-scale James Webb Space Telescope model on display at SXSW in Austin, Texas, on March 8, 2013. Gunn: "This was the first time I realized how massive the telescope was going to be, both in size and impact on the world. The model fascinated everyone at SXSW that year." #

Dressed in a clean-room suit, NASA photographer Desiree Stover shines a light on the Space Environment Simulator's Integration Frame inside the thermal vacuum chamber at NASA's Goddard Space Flight Center in Greenbelt, Maryland, on August 29, 2013. Shortly after, the chamber was closed up and engineers used this frame to enclose and help cryogenic-test the Integrated Science Instrument Module. #

Dressed in a clean room suit to prevent contamination, optics technician Jeff Gum aligns a replacement Focal Plane Assembly with a powerful three-dimensional microscope at NASA's Goddard Space Flight Center in Greenbelt, Maryland, on September 12, 2013. This FPA will be installed on the Near Infrared Camera (NIRCam) instrument, which has unique components that are individually tailored to see in a particular infrared wavelength range. #

A robotic arm lowers a golden James Webb Space Telescope flight spare primary mirror segment onto a test piece of backplane at NASA's Goddard Space Flight Center on November 7, 2013. While the team practices the positioning that will be done on the actual telescope in the cleanroom, Dave Sime, an assembly crew chief, inspects the mirror placement from the underside of the backplane. #

Group photo of JWST project members with the complete Integrated Science Instrument Module. The Near Infrared Spectrograph was just added, completing the package of four instruments including a Near Infrared Camera, a Mid Infrared Instrument, a Fine Guidance Sensor, and two different Near Infrared Spectrographs, photographed on March 25, 2014. #

Access into a clean room to get a close-up view of a complicated, high-value scientific instrument is carefully controlled, but NASA photographers get such exclusive entry all the time. Photographer Chris Gunn took this image of the NIRSpec instrument inside the giant clean room at NASA's Goddard Space Flight Center on March 25, 2014. The Near-Infrared Spectrograph or NIRSpec is a multi-object spectrograph, which is a tool for observing many objects in the cosmos simultaneously. The NIRSpec takes in light from around 100 distant objects and records their spectra (band of colors produced when sunlight is passed through a prism), separating the light into its components using prisms and other optical devices. In the photo, the NIRSpec is the large silver mass on the right-hand side. The silver frame-like object on the left side is part of the ISIM structure. NIRSpec weighs about 430 pounds (195 kilograms), about as much as an upright piano. It is one of four instruments that will fly aboard the Webb telescope. #

"This is what space science is all about," said photographer Chris Gunn, who captured a photo from outside the enormous mouth of NASA's giant thermal vacuum chamber, called Chamber A, at Johnson Space Center in Houston on September 9, 2014. Previously used for manned-spaceflight missions, this historic chamber is now filled with engineers and technicians preparing for the James Webb Space Telescope mission. Inside, engineers and technicians prepare a lift system that will be used to hold JWST during testing. "There is nothing else like this that anyone will see in their day-to-day lives," said Gunn. "This was the first time that I had photographed the interior of the historic Chamber A. Looking at the chamber as a single subject, it's probably the largest thing I’d ever photographed for the project. Lighting the chamber was a challenge; I settled on placing a remotely triggered light directly above the work. What’s amazing to me is that everyone is in motion." #

Inside Goddard Space Flight Center's giant clean room, JWST Optical Engineer Larkin Carey examines two test-mirror segments recently placed on a black composite structure on September 29, 2014. This black composite structure is called the James Webb Space Telescope's “pathfinder,” and acts as a spine supporting the telescope's primary mirror segments. The Pathfinder is a non-flight prototype. "Getting this right is critical to proving we are ready to start assembling the flight mirrors onto the flight structure next summer," said Lee Feinberg, NASA's Optical Telescope Element manager at NASA Goddard. "This is the first space telescope that has ever been built with a light-weighted segmented primary mirror, so learning how to do this is a groundbreaking capability for not only the Webb telescope, but for potential future space telescopes." #

Just like drivers sometimes use snow to clean their car mirrors in winter, two Exelis, Inc. engineers practice "snow cleaning'" on a test telescope mirror for the James Webb Space Telescope at NASA's Goddard Space Flight Center on January 22, 2015. By shooting carbon dioxide snow at the surface, engineers are able to clean large telescope mirrors without scratching them. "The snow-like crystals (carbon dioxide snow) knock contaminate particulates and molecules off the mirror," said Lee Feinberg, NASA Optical Telescope Element manager. Gunn: "Super fun to watch and capture this process. It’s apparently a common process in aerospace. The test was successful but will probably never be used on the full telescope." #

The fifth floor of Chamber A at Johnson Space Center, photographed on May 20, 2015. Chamber A is the giant thermal vacuum test chamber that will be used for an end-to-end test of the James Webb Space Telescope in 2017. This photo was taken before the start of a test on the Webb telescope Pathfinder. The contamination control engineer on the left is doing his final FOD (Foreign Object Debris) inspection. In the center of this image, wrapped in the silver thermal blanketing, is the CoCoa (Center of Curvature optical assembly). CoCoa tests on the Webb telescope's concave mirror segments are critical because they will tell engineers if all of the mirrors work together to make a telescope that has the correct shape. Gunn: "This view was unexpected and just really cool. It really looked like a set from a science-fiction movie. In the center of the frame, behind the blanketing, is the aperture central to the cryogenic optical testing for the telescope." #

Inside the clean room on the morning of April 25, 2016, primary mirrors are uncovered in preparation for instrument installation. The covers are just lightly fastened and protect the mirrors while they are face-up. Technicians were preparing to rotate JWST so the mirrors are face-down, to allow the installation of instruments behind the primary mirror. Gunn: "This image was made approximately three months after the first mirror was installed onto the backplane. It was one of the most anticipated moments on the project. Pretty sure I held my breath the entire time. The two technicians removing the covers practiced their moves for a couple of weeks prior to this day." #

Engineers Matt Macias and Eve Woolridge take a close look at the JWST primary mirror at NASA Goddard on May 2, 2016. The secondary mirror is the round mirror located at the end of the long booms, which are folded into their launch configuration. Gunn: "This is still one of my favorite photos of Webb, made days after the mirrors were uncovered. The schedule called for an evening of lights-out inspections and I seized the opportunity to make this dramatic photograph showing the engineers’ flashlight beam skimming the surface of the telescope." #

Clean-room workers pose for a quick group photo with the JWST mirrors on May 4, 2016. The telescope structure and mirrors were in the process of being rotated face-down, the configuration necessary for installing the science instruments behind the giant golden primary mirror. The mirrors, which are actually made of beryllium, are covered with a microscopically thin layer of gold, which optimizes them for reflecting infrared light. This photo also helps give a scale to JWST— the primary mirror is some 6.5 meters in diameter. The telescope will eventually be mated to a sunshield that is the size of a tennis court. #

Engineers and technicians working on Webb successfully completed the first important optical measurement of its fully assembled primary mirror, called a Center of Curvature test on October 14, 2016. Taking a “before” optical measurement of the telescope’s deployed mirror is crucial before the telescope goes into several stages of rigorous mechanical testing. These tests will simulate the violent sound and vibration environments the telescope will experience inside its rocket on its way out into space. This environment is one of the most stressful structurally and could alter the shape and alignment of Webb’s primary mirror, which could degrade or, in the worst case, ruin its performance. Gunn: "The Goddard film crew and I had the rare opportunity to spend an evening with the telescope making images. This photograph is special to me for a bunch of reasons, but one of the main ones is that the technician pictured on the shot, George Mooney, has been a constant fixture on the project since integration began." #

A clean tent is lowered over the JWST on November 16, 2016. The clean tent protects the telescope from dust and dirt when engineers at NASA's Goddard Space Flight Center transport the next-generation space telescope out of the relatively dust-free clean room and into the shirtsleeve environment of the vibration and acoustics testing areas. Gunn: "One of my favorites, as it really captures what the big moments feel like. Everyone in the room has a role and is a stakeholder in the process. You can't tell here but there are multiple teams coming together to move the telescope into its testing phase, which will happen outside of the clean room." #

Technicians inspecting the JWST look like ghostly wraiths in this image as they conduct a lights-out inspection in the Spacecraft Systems Development and Integration Facility at Goddard Space Flight Center on March 5, 2017. The clean-room lights were turned off to inspect the telescope after it experienced vibration and acoustic testing. The contamination control engineer used a bright flashlight and special ultraviolet flashlights to inspect for contamination, because it's easier to find in the dark. Gunn: "I was on standby to shoot as needed while contamination-control engineers performed a lights-out inspection, and I just decided to have a little fun and leave the shutter open for a while. Added in a few pops from a strobe and got this really cool result." #

The JWST arrives at Ellington Field, in Houston, Texas, from Joint Base Andrews in Maryland, on May 7, 2017. The telescope was safely ensconced in a special transporter case (called the Space Telescope Transporter for Air, Road, and Sea, or STTARS) which attaches to a truck. Webb was first driven from NASA Goddard to Andrews, and then put in a C-5 cargo plane. The plane flew to Ellington, and then the telescope was transported by truck to NASA's Johnson Space Center for an end-to-end cryogenic test. #

Webb is lifted onto its test stand inside Chamber A at NASA's Johnson Space Center on May 20, 2017. It will eventually be slid into the chamber for cryogenic testing. Gunn: "The chamber is awesome from the outside but the inside is breathtaking … just wanted to convey a little bit of that feeling." #

Chamber A’s massive vault-like door towers over engineers at NASA’s Johnson Space Center in Houston. Gunn: "I fought to get in position so I’d be in the center of the door by moving a 24-foot ladder across the floor just in time to catch these three waling across the floor." #

Engineers inspect the James Webb Space Telescope as it sits inside Chamber A at NASA’s Johnson Space Center on November 19, 2017. Webb completed its final cryogenic testing inside that chamber on November 18, 2017. Gunn: "After 100 days of testing in the chamber, it was like seeing an old friend ... for the entire project and public. In order to achieve illumination on the primary mirror, I had to light the back wall of the chamber." #

The combined optical element and science instruments of NASA’s James Webb Space Telescope are removed from their specially designed STTARS shipping container in a high bay at Northrop Grumman in Redondo Beach, California, on March 8, 2018. Northrop is the final step of Webb’s journey before it travels to its launch site in Kourou, French Guiana, for a launch scheduled in the spring of 2019. Engineers will conduct final testing at the facility to ensure the observatory is ready for space. These final tests at Northrop are critical to making sure the fully assembled observatory deploys and operates as expected in space. To reach space, the telescope must fold origami-style inside its Ariane 5 rocket for launch. Once in space and detached from the rocket’s payload adaptor, Webb must successfully unfold its sunshield and deploy its mirrors, including its highly complex primary mirror, to become active. #