The James Webb Space Telescope: a 6.5-metre segmented mirror observing infrared light from the L2 point

Background

The James Webb Space Telescope (JWST, or Webb) is a joint project between NASA, ESA and the Canadian Space Agency (CSA). It has a segmented primary mirror with a diameter of 6.5 metres that collects almost six times more light than the Hubble Space Telescope. The wavelength range covered by its scientific instruments is about 0.6 μm to 28 μm (visible to mid-infrared light), while the Hubble Space Telescope observes at 0.1–2.5 microns. Webb carries four 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. The observatory operates approximately 1.5 million kilometres from Earth, in an orbit around the second Lagrange point of the Sun-Earth system, L2. A giant, five layered shield of 22×12 metres keeps the telescope and its instruments permanently in the shade, where they cool down to –233 °C; MIRI is cooled further, to –266 °C. The telescope launched on 25 December 2021 on an Ariane 5 ECA rocket from Europe's Spaceport in French Guiana. The mission honours NASA's second administrator, James E. Webb, and was previously known as the Next Generation Space Telescope (NGST). In return for Europe's contributions, European scientists get a minimum share of 15% of the total observing time.