The James Webb Space Telescope’s spacecraft element just prior to being transported to nearby acoustic, and vibration test facilities at Northrop Grumman in Redondo Beach, California. Credits: NASA's Goddard Space Flight Center/Chris Gunn more info: https://www.nasa.gov/feature/goddard/2019/nasa-s-webb-is-sound-after-completing-critical-milestones

A view of the one dozen (out of 18) flight mirror segments that make up the primary mirror on NASA's James Webb Space Telescope have been installed at NASA's Goddard Space Flight Center. Credits: NASA/Chris Gunn More: Since December 2015, the team of scientists and engineers have been working tirelessly to install all the primary mirror segments onto the telescope structure in the large clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The twelfth mirror was installed on January 2, 2016. "This milestone signifies that all of the hexagonal shaped mirrors on the fixed central section of the telescope structure are installed and only the 3 mirrors on each wing are left for installation," said Lee Feinberg, NASA's Optical Telescope Element Manager at NASA Goddard. "The incredibly skilled and dedicated team assembling the telescope continues to find ways to do things faster and more efficiently." Each hexagonal-shaped segment measures just over 4.2 feet (1.3 meters) across and weighs approximately 88 pounds (40 kilograms). After being pieced together, the 18 primary mirror segments will work together as one large 21.3-foot (6.5-meter) mirror. The primary mirror will unfold and adjust to shape after launch. The mirrors are made of ultra-lightweight beryllium. The mirrors are placed on the telescope's backplane using a robotic arm, guided by engineers. The full installation is expected to be completed in a few months. The mirrors were built by Ball Aerospace & Technologies Corp., Boulder, Colorado. Ball is the principal subcontractor to Northrop Grumman for the optical technology and lightweight mirror system. The installation of the mirrors onto the telescope structure is performed by Harris Corporation of Rochester, New York. Harris Corporation leads integration and testing for the telescope. While the mirror assembly is a very significant milestone, there are many more steps involved in assembling the Webb telescope. The primary mirror and the tennis-court-sized sunshield are the largest and most visible components of the Webb telescope. However, there are four smaller components that are less visible, yet critical. The instruments that will fly aboard Webb - cameras and spectrographs with detectors able to record extremely faint signals — are part of the Integrated Science Instrument Module (ISIM), which is currently undergoing its final cryogenic vacuum test and will be integrated with the mirror later this year.

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 in Greenbelt, Maryland. 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. This technique will only be used if the James Webb Space Telescope's mirror is contaminated during integration and testing. The Webb telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. With a mirror seven times as large as Hubble's and infrared capability, Webb will be capturing light from 13.5 billion light years away. To do this, its mirror must be kept super clean. "Small dust particles or molecules can impact the science that can be done with the Webb," said Feinberg. "So cleanliness especially on the mirrors is critical." Webb is an international project led by NASA with its partners, the European Space Agency and the Canadian Space Agency. Image credit: NASA/Goddard/Chris Gunn

To keep Webb’s spacecraft element and its sensitive instruments contaminant free, technicians and engineers enclose it in a protective clamshell that serves as a mobile clean room while in transport. Credits: NASA's Goddard Space Flight Center/Chris Gunn more info: https://www.nasa.gov/feature/goddard/2019/nasa-s-webb-is-sound-after-completing-critical-milestones

Arianespace's Ariane 5 rocket launches with NASA’s James Webb Space Telescope onboard, Saturday, Dec. 25, 2021, from the ELA-3 Launch Zone of Europe’s Spaceport at the Guiana Space Centre in Kourou, French Guiana. The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with a 21.3 foot (6.5 meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Photo Credit: (NASA/Chris Gunn)

Arianespace's Ariane 5 rocket launches with NASA’s James Webb Space Telescope onboard, Saturday, Dec. 25, 2021, from the ELA-3 Launch Zone of Europe’s Spaceport at the Guiana Space Centre in Kourou, French Guiana. The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with a 21.3 foot (6.5 meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Photo Credit: (NASA/Chris Gunn)

Prince Philip, left, speaks with veteran space walkers John M. Grunsfeld, center, and Michael J. Massimino at NASA's Goddard Space Flight Center. Photo Credit: (NASA/Chris Gunn)

Prince Philip, left, asks astronauts K. Megan McArthur, Commander Scott D. Altman and Gregory C. Johnson, pilot details about the STS-125 mission. Photo Credit: (NASA/Chris Gunn)

Arianespace's Ariane 5 rocket with NASA’s James Webb Space Telescope onboard, is seen in the final assembly building ahead of the planned roll to the launch pad, Thursday, Dec. 23, 2021, at Europe’s Spaceport, the Guiana Space Center in Kourou, French Guiana. The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with a 21.3 foot (6.5 meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Photo Credit: (NASA/Chris Gunn)

Preston Burch, left, Hubble Spece Telescope Program Manager presents Prince Philip with three solar cells returned from space during the first HST servicing mission. Photo Credit: (NASA/Chris Gunn)

Arianespace's Ariane 5 rocket with NASA’s James Webb Space Telescope onboard, is seen in the final assembly building ahead of the planned roll to the launch pad, Thursday, Dec. 23, 2021, at Europe’s Spaceport, the Guiana Space Center in Kourou, French Guiana. The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with a 21.3 foot (6.5 meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Photo Credit: (NASA/Chris Gunn)

Connor Trinner Tours Hubble F in # 29

Actor Connor Trinneer, right, tours the high bay clean room in Building 29 at NASA's Goddard Space Flight Center in Greenbelt, Md. Trinneer is best known for his role as Chief Engineer "Trip" Tucker in the TV show "Star Trek: Enterprise."

Arianespace's Ariane 5 rocket launches with NASA’s James Webb Space Telescope onboard, Saturday, Dec. 25, 2021, from the ELA-3 Launch Zone of Europe’s Spaceport at the Guiana Space Centre in Kourou, French Guiana. The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with a 21.3 foot (6.5 meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Photo Credit: (NASA/Chris Gunn)

Space shuttle Discovery, mounted atop a NASA 747 Shuttle Carrier Aircraft (SCA) is seen from Top of the Town in Arlington, Virginia as it flies near the U.S. Capitol, Tuesday, April 17, 2012, in Washington. Discovery, the first orbiter retired from NASA’s shuttle fleet, completed 39 missions, spent 365 days in space, orbited the Earth 5,830 times, and traveled 148,221,675 miles. NASA will transfer Discovery to the National Air and Space Museum to begin its new mission to commemorate past achievements in space and to educate and inspire future generations of explorers. Photo Credit: (NASA/Chris Gunn)

Prince Philip greets astronauts from STS-125 L to R Andrew J Feustel, Michael T Goode, K. Megan McArthur, Michael J. Massimino, Gregory C. Johnson, and Commander Scott D. Altman. Photo Credit: (NASA/Chris Gunn)

Arianespace's Ariane 5 rocket with NASA’s James Webb Space Telescope onboard, is seen in the final assembly building ahead of the planned roll to the launch pad, Thursday, Dec. 23, 2021, at Europe’s Spaceport, the Guiana Space Center in Kourou, French Guiana. The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with a 21.3 foot (6.5 meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Photo Credit: (NASA/Chris Gunn)

Solar Dynamics Observatory Program Manager, left, describes the SDO project to Prince Philip in front of the spacecraft clean tent. Photo Credit: (NASA/Chris Gunn)

Arianespace's Ariane 5 rocket with NASA’s James Webb Space Telescope onboard, is seen at the launch pad, Thursday, Dec. 23, 2021, at Europe’s Spaceport, the Guiana Space Center in Kourou, French Guiana. The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with a 21.3 foot (6.5 meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Photo Credit: (NASA/Chris Gunn)

Actor Connor Trinneer tours the high bay clean room in Building 29 at NASA's Goddard Space Flight Center in Greenbelt, Md. Trinneer is best known for his role as Chief Engineer "Trip" Tucker in the TV show "Star Trek: Enterprise."