ESA title
Science & Exploration

JWST factsheet

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ESA / Science & Exploration / Space Science

Mission Exploring the Universe from the solar neighbourhood to the most distant galaxies.

Name The James Webb Space Telescope honours NASA's second administrator, James E. Webb, who headed the agency during part of the Apollo era, from February 1961 to October 1968. The James Webb Space Telescope (JWST) was originally known as the Next Generation Space Telescope (NGST).

Partnership JWST is a joint project between NASA, ESA and the Canadian Space Agency (CSA).

Description JWST is a major space observatory often presented as the successor to the very successful NASA/ESA Hubble Space Telescope (HST). It has a large 6.5-metre segmented mirror that will collect almost 6 times more light than HST. It has also been designed to work with infrared light. It will address a broad variety of scientific topics ranging from detecting the first galaxies in the Universe to studying planets around other stars.

Instruments JWST will carry four state-of-the-art science instruments: the MIRI mid-infrared camera and spectrograph, the NIRSpec near-infrared spectrograph, the NIRCam near-infrared camera, and the FGS-NIRISS combined fine guidance sensor and near-infrared imager and slitless spectrograph.

Launch JWST is working toward a launch on 30 March 2021 on an Ariane 5 ECA rocket from ESA’s spaceport at Kourou in French Guiana.

Journey and orbit After launch and after 1 month on a transfer trajectory, the observatory will operate at approximately 1.5 million kilometres from Earth, in an orbit around the second Lagrange point of the Sun-Earth system, L2.

European contribution to JWST The four major contributions of Europe to the mission are: the provision of the NIRSpec instrument; the provision of the MIRI instrument optical bench assembly; the provision of the launcher; and the provision of manpower to support JWST operation. In return for these contributions, European scientists will get a minimum share of 15% of the total JWST observing time, like for HST.

JWST mission facts

Scientists expect JWST to find out more about the origins of the Universe by observing infrared light from the first stars and galaxies.

Scientists will use JWST to study the properties of planets around other stars, including looking for the signature of water in their atmosphere.

JWST's wavelength range will be from about 0.6 to 28 microns (visible to the mid-infrared light). By comparison, the Hubble Space Telescope observes at 0.1-2.5 microns (ultraviolet to the near infrared).

JWST will have a segmented primary mirror with a diameter of 6.5 metres that will collect almost 6 times more light than the Hubble Space Telescope.

JWST has a sun-shield the size of a tennis court, which is used to keep the telescope and its instruments permanently in the shade where they will cool down to -233ºC.

JWST scientists have described packing a 6.5-metre telescope equipped with a sun-shield the size of a tennis court into a small rocket fairing with a diameter of five metres as “a bit like designing a ship in a bottle”.

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