Home > James Webb Space Telescope
James Webb Space Telescope
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| Organization | NASA, ESA, CSA |
| Wavelength regime | infrared |
| Orbit height | 1.5106km from Earth
(L2 Lagrangian point) |
| Orbit period | 1 year |
| Launch date | (August 2011) |
| Deorbit date | ( 2016 - 2021) |
| Mass | 6,200kg |
| Other names | Next Generation Space Telescope |
| Webpage | http://www.jwst.nasa.gov |
| Physical Characteristics |
| Telescope Style | (refractor, Newtonian reflector, etc.) |
| Diameter | ~6.5m |
| Collecting Area | 25m2 |
| Focal Length | (m, ft) |
| Instruments |
| NIRCam | Near IR Camera |
| NIRSpec | Near IR Spectrograph |
| MIRI | Mid IR Instrument |
| FGS | Fine Guidance Sensors |
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 sometime between 2009 and 2011.
1 Mission
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.
2 Orbit
In order to keep the Earth and Sun at the same location in the telescope's "sky", it will be placed in orbit at the L2 lagrangian point. This location, around 1.5 million km from Earth, is considerably beyond the maximum altitude achievable using the Space Shuttle, so JWST will probably be placed in orbit using a European Ariane 5The Ariane 5 is an expendable launch system, designed by the European Space Agency (ESA) and manufactured, operated and marketed by Arianespace as part of the Ariane programme. Arianespace builds the rockets in Europe and launches from a space port at Kou launcher. This distance also means that, unlike Hubble, it will not be possible to repair or upgrade the observatory during its 5-10 year design life. Although the L2 point is well outside the orbit of the MoonFor other moons in the solar system see natural satellite. For other uses see Moon (disambiguation). The Moon is the only natural satellite of Earth. It has no formal name other than "The Moon" although it is occasionally called Luna ( Latin for moon to d, JWST will still need a sunshade to avoid the faint heat of reflected moonlight.
3 Optics
Although JWST has a planned weight half that of the Hubble, its primary mirror (a 6.5 meter berylliumBeryllium is the chemical element in the periodic table that has the symbol Be and atomic number 4. A toxic bivalent element, beryllium is a steel grey, strong, light-weight yet brittle, alkaline earth metal, that is primarily used as a hardening agent in 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 KeckKeck telescopes are the two largest telescopes of the Mauna Kea Observatory on Mauna Kea in Hawai'i. These are reflecting telescopes located at an altitude of 4,145 m (13,600 ft). Keck I started observing in 1993 and Keck II started in 1996. This is a Rit which continually adjust their mirror segments to overcome atmospheric scintillation.
