James Webb Space Telescope
James Webb Space Telescope rendering
A rendering of the James Webb Space Telescope with its components fully deployed
Mission typeAstronomy
OperatorNASA / ESA / CSA / STScI[1]
Mission duration5 years (design)
10 years (goal)
Spacecraft properties
ManufacturerNorthrop Grumman
Ball Aerospace
Launch mass6,500 kg (14,300 lb)[2]
Dimensions20.197 m × 14.162 m (66.26 ft × 46.46 ft) (sunshield)
Power2,000 watts
Start of mission
Launch date30 March 2021 (planned)[3]
RocketAriane 5 ECA
Launch siteKourou ELA-3
Orbital parameters
Reference systemSun–Earth L2
RegimeHalo orbit
Periapsis altitude374,000 km (232,000 mi)[4]
Apoapsis altitude1,500,000 km (930,000 mi)[4]
Period6 months
TypeKorsch telescope
Diameter6.5 m (21 ft)
Focal length131.4 m (431 ft)
Collecting area25.4 m2 (273 sq ft)[5]
Wavelengthsfrom 0.6 µm (orange)
to 28.5 µm (mid-infrared)
BandS-band (TT&C support)
Ka band (data acquisition)
BandwidthS-band up: 16 kbit/s
S-band down: 40 kbit/s
Ka band down: up to 28 Mbit/s
JWST logo
James Webb Space Telescope insignia  

The James Webb Space Telescope (JWST or "Webb") is a space telescope that is planned to be the successor to the Hubble Space Telescope.[6][7] The JWST will provide greatly improved resolution and sensitivity over the 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. Other goals include understanding the formation of stars and planets, and direct imaging of exoplanets and novas.[8]

The primary mirror of the JWST, the Optical Telescope Element, is composed of 18 hexagonal mirror segments which combine to create a 6.5-meter (21 ft; 260 in) diameter mirror that is much larger than the Hubble's 2.4-meter (7.9 ft; 94 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 27 μm), which will allow it to observe high redshift objects that are too old and too distant for the Hubble to observe.[9] 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 will keep its mirror and instruments below 50 K (−220 °C; −370 °F).[10]

The JWST is being developed by NASA—with significant contributions from the European Space Agency and the Canadian Space Agency[1]—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.[11][12] Development began in 1996 for a launch that was initially planned for 2007, 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.[13][14] In March 2018, NASA delayed the launch after the telescope's sunshield ripped during a practice deployment.[15] Launch was delayed again in June 2018 following recommendations from an independent review board, and is currently scheduled for March 2021.[3][16][17] On 28 August 2019, it was confirmed by NASA that construction was completely finished.[18]


Launch configuration of the JWST in an Ariane 5.

The JWST has an expected mass about half of Hubble Space Telescope's, but its primary mirror (a 6.5 meter diameter gold-coated beryllium reflector) will have a collecting area about five times as large (25 m2 or 270 sq ft vs. 4.5 m2 or 48 sq ft). The JWST is oriented toward near-infrared astronomy, but can also see orange and