The James Webb Space Telescope (JWST) is a planned orbital infrared observatory, intended (in part) to replace the aging Hubble Space Telescope. Formerly called the Next Generation Space Telescope (NGST), it was renamed after NASA's second administrator, James E. Webb, in 2002. The telescope's launch is planned for 2011.
The JWST's primary mission is to examine the infrared remnants of the big bang, and thus to make observations of an earlier state of the universe than is possible today. To achieve this, sensors of unparalleled sensitivity will be used, which in turn requires that the entire spacecraft be particularly cold, and that major sources of IR interference (notably the Sun, the Earth, and the Moon) be blocked. To this end, JWST will be accompanied by a large metalized fanfold sunshield, which will unravel to block infrared radiation from these sources. The telescope's lagrangian orbit (see below) ensures that the Earth and Sun occupy the same relative position in the telescope's view, and thus make the operation of this shield possible.
Optics
Although JWST has a planned weight half that of the Hubble, its primary mirror (a 6.5 meter beryllium reflector) is more than 5 times larger. As this diameter is much larger than any current launch vehicle, the mirror is composed of 18 segments, which will unfold after the telescope is launched. Sensitive micromotors and wavefront sensors will position the mirror segments in the correct location, but subsequent to this initial configuration they will only rarely be moved; unlike terrestrial telescopes like the Keck which continually adjust their mirror segments to overcome atmospheric scintillation.
The JamesWebb Space Telescope (JWST) is a planned space infrared observatory, intended to be a significant improvement on the aging Hubble Space Telescope.
Due to a combination of redshift, dust obscuration, and the intrinsically low temperatures of many of the sources to be studied, the JWST must operate at infrared wavelengths, spanning the wavelength range from 0.6 to 28 micrometres.
The telescope's location at the Sun-Earth L2 Lagrange point ensures that the Earth and Sun occupy roughly the same relative position in the telescope's view, and thus make the operation of this shield possible.
The JamesWebb testbed telescope, housed at Ball Aerospace's Boulder, Colo. facilities, will aid engineers in developing and simulating the telescope's Wavefront Sensing and Control System used to align the mirrors in the optical system and provide fine-tuning of the focus.
JamesWebb will be the first space-based telescope to use this segmented mirror architecture.
The JamesWebb Space Telescope was designed to study infrared light from objects that formed in the beginning of the universe.
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