James Webb Space Telescope: large deployable cryogenic telescope in space

Abstract

The James Webb Space Telescope (JWST) is an infrared space telescope designed to explore four major science themes: first light and reionization, the assembly of galaxies, the birth of stars and proto- planetary systems, and planetary systems and origins of life. JWST is a segmented architecture telescope with an aperture of 6.6 m. It will operate at cryogenic temperature (40 K), achieved via passive cooling, in an orbit about the Earth-Sun second Lagrange point (L2). Passive cooling is facili- tated by means of a large sunshield that provides thermal isolation and protection from direct illumination from the Sun. The large size of the tele- scope and spacecraft systems require that they are stowed for launch in a configuration that fits the Ariane 5 fairing, and then deployed after launch. Routine wavefront sensing and control measurements are used to achieve phasing of the segmented primary mirror and initial alignment of the telescope. A suite of instruments will provide the capability to observe over a spectral range from 0.6- to 27-μm wavelengths with imaging and spectroscopic configurations. An overview is presented of the architecture and selected optical design features of JWST are described.