James Webb Space Telescope
|
|
| |
| Organization | NASA, ESA, CSA |
|---|---|
| Wavelength regime | infrared |
| Orbit height | 1.5×106km 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. It will be jointly constructed and operated by ESA and NASA. 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.
| Contents |
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.
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 using active optics to overcome the effects of gravitational loading and wind loading.
Current Status
Funding difficulties caused partly by the increased cost of JWST and of other NASA missions such as for Mars exploration and potential servicing of the Hubble Space Telescope mean that the JWST mission is likely to be reduced in scope. The proposed descope of the JWST from 6.5m to 4m has been abandoned, but other cost-cutting measures are still on the table.
Construction & Engineering
The primary instrument of the telescope, the NIRcam (Near InfraRed Camera), will be built by a team led by the University of Arizona, with Principal Investigator Dr. Marcia Rieke. The industrial partner is Lockheed-Martin's Advanced Technology Center located in Palo Alto, California.
See also
External links
- JWST homepage at NASA (http://www.jwst.nasa.gov/)
- Cost overruns put squeeze on Hubble’s successor (http://www.newscientist.com/article.ns?id=dn7423)de:James Webb Space Telescope