page_title: James Webb Space Telescope
hierarchical_section_title: James Webb Space Telescope
caption_attribution_description: English: Illustration of the James Webb Space Telescope on a transparent background.
context_page_description: The James Webb Space Telescope is a space telescope that is planned to succeed the Hubble Space Telescope as NASA's flagship astrophysics mission. The JWST will provide improved infrared resolution and sensitivity over Hubble, and will enable a broad range of investigations across the fields of astronomy and cosmology, including observing some of the most distant events and objects in the universe, such as the formation of the first galaxies.
  The primary mirror of the JWST, the Optical Telescope Element, is composed of eighteen 1.32-metre hexagonal mirror segments made of gold-plated beryllium which combine to create a 6.5-metre diameter mirror that is considerably larger than the Hubble's 2.4-metre mirror. Unlike the Hubble, which observes in the near ultraviolet, visible, and near infrared spectra, the JWST will observe in a lower frequency range, from long-wavelength visible light through mid-infrared, which will allow it to observe high redshift objects that are too old and too distant for the Hubble to observe.
context_section_description: The James Webb Space Telescope (JWST or "Webb") is a space telescope that is planned to succeed the Hubble Space Telescope as NASA's flagship astrophysics mission. The JWST will provide improved infrared resolution and sensitivity over Hubble, and will enable a broad range of investigations across the fields of astronomy and cosmology, including observing some of the most distant events and objects in the universe, such as the formation of the first galaxies.
  The primary mirror of the JWST, the Optical Telescope Element, is composed of eighteen 1.32-metre (4 ft 4 in) hexagonal mirror segments made of gold-plated beryllium which combine to create a 6.5-metre (21 ft) diameter mirror that is considerably larger than the Hubble's 2.4-metre (7 ft 10 in) mirror. Unlike the Hubble, which observes in the near ultraviolet, visible, and near infrared (0.1 to 1 μm) spectra, the JWST will observe in a lower frequency range, from long-wavelength visible light through mid-infrared (0.6 to 28.3 μm), which will allow it to observe high redshift objects that are too old and too distant for the Hubble to observe. The telescope must be kept very cold in order to observe in the infrared without interference, so it will be deployed in space near the Earth–Sun L₂ Lagrangian point, and a large sunshield made of silicon-coated and aluminium-coated Kapton will keep its mirror and instruments below 50 K (−220 °C; −370 °F).
  The JWST is being developed by NASA — with significant contributions from the European Space Agency and the Canadian Space Agency — and is named for James E. Webb, who was the administrator of NASA from 1961 to 1968 and played an integral role in the Apollo program. The prime contractor is Northrop Grumman.
  Development began in 1996 for a launch that was initially planned for 2007 and a 500-million-dollar budget, but the project has had numerous delays and cost overruns, and underwent a major redesign in 2005. The JWST's construction was completed in late 2016, after which its extensive testing phase began. In March 2018, NASA further delayed the launch after the telescope's sunshield ripped during a practice deployment. Launch was delayed again in June 2018 following recommendations from an independent review board. Work on integration and testing of the telescope was suspended in March 2020 due to the COVID-19 pandemic, adding further delays. Work has resumed, but NASA announced that the launch date has once again been delayed to 31 October 2021.
caption: A rendering of the James Webb Space Telescope with its components fully deployed.
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