James Webb Space Telescope

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This article or section contains information regarding a future spaceflight.
Due to the nature of the content, details may change dramatically as the launch date approaches and/or more information becomes available.

**James Webb Space Telescope**
Physical characteristics

Organization	NASA, ESA, CSA
Wavelength regime	Infrared (IR)
Orbit height	1.5×10⁶ km from Earth (L2 Lagrangian point)
Orbit period	1 year
Launch date	(June 2013)
Mission length	5 years (design) 10 years (goal)
Mass	6,200 kg
Other names	Next Generation Space Telescope
Webpage	http://www.jwst.nasa.gov
Telescope style	Cassegrain Reflector
Diameter	~6.5 m
Collecting area	25 m²
Focal length	131.4 m (431.1 ft)
Instruments
NIRCam	Near IR Camera
NIRSpec	Near IR Spectrograph
MIRI	Mid IR Instrument
FGS	Fine Guidance Sensor

The James Webb Space Telescope (JWST) is a planned space infrared observatory, intended to be a significant improvement on the aging Hubble Space Telescope. It will be constructed and operated by NASA with help from ESA and CSA. Formerly called the Next Generation Space Telescope (or NGST), it was renamed after NASA's second administrator, James E. Webb, in 2002. The telescope's launch is planned for no earlier than June 2013. It will be launched on an Ariane 5 rocket.^[1]

1 Mission
2 Optics
3 Current status
4 Construction and engineering
5 See also
6 References
7 External links

[edit] Mission

The JWST's primary scientific mission has four main components: to search for light from the first stars and galaxies which formed in the Universe after the Big Bang; to study the formation and evolution of galaxies; to understand the formation of stars and planetary systems; and to study planetary systems and the origins of life. 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. In order to ensure that the observations are not hampered by infrared emission from the telescope and instruments themselves, the entire observatory must be cold, well-shielded from the Sun so that it can radiatively cool to roughly 50 kelvins (−220 °C, −370 °F). To this end, JWST will incorporate a large metalized fanfold sunshield, which will unfurl to block infrared radiation from the Sun, as well as from the Earth and Moon. 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 observatory is due to be launched no earlier than June 2013 and is currently scheduled to be launched by an Ariane 5 from Kourou into an L2 orbit with a launch mass of approximately 6.2 metric tons. After a commissioning period of approximately 6 months, the observatory will begin the science mission, which will be required to last a minimum of 5 years. The potential for extension of the science mission beyond this period exists, and the observatory is being designed accordingly.

[edit] Optics

Although JWST has a planned mass half that of the Hubble, its primary mirror (a 6.5 meter diameter beryllium reflector) has a collecting area which is almost 6 times larger. As this diameter is much larger than any current launch vehicle, the mirror is composed of 18 hexagonal segments, which will unfold after the telescope is launched. Sensitive micromotors and a wavefront sensor will position the mirror segments in the correct location, but subsequent to this initial configuration they will only rarely be moved; this process is therefore much like an initial calibration, unlike terrestrial telescopes like the Keck which continually adjust their mirror segments using active optics to overcome the effects of gravitational and wind loading.

Ball Aerospace & Technologies Corp. is the principal optical subcontractor for the JWST program, led by prime contractor Northrop Grumman Space Technology, under a contract from the NASA Goddard Space Flight Center, in Greenbelt, MD. Seventeen additional primary mirror segments, secondary, and tertiary mirrors, plus flight spares, will be delivered to Ball Aerospace from its beryllium mirror manufacturing team that includes Axsys, Brush Wellman, and Tinsley Laboratories. As each additional mirror is delivered to Ball Aerospace over the next four years (to 2010), it will be mounted onto a lightweight, actuated strong-back assembly and undergo functional and environmental testing.

[edit] Current status

The JWST program is in its preliminary design phase (Phase B). In January 2007 the program is scheduled to undergo a non-advocate review in order to determine if the proposed technologies are sufficiently mature to begin the next phase. This technology review represents the beginning step in the process that will ultimately move the program into its detailed design phase (Phase C). In April 2006 the program was independently reviewed following a replanning phase begun in August 2005. The review concluded the program was technically sound, but that funding phasing at NASA needed to be changed. NASA has rephased its JWST budgets accordingly. The August 2005 replanning was necessitated by the cost growth revealed in Spring 2005. The primary technical outcomes of the replanning are significant changes in the integration and test plans, a 22-month launch delay (from 2011 to 2013), and elimination of system level testing for observatory modes at wavelength shorter than 1.7 micrometres. Other major features of the observatory are unchanged following the replanning efforts.

In May 2005 the cost of the project was estimated at about US$ 3.5 Billion.

[edit] Construction and engineering

NASA's Goddard Space Flight Center in Greenbelt, Maryland is leading the management of the observatory project. The project scientist for the James Webb Space Telescope is Dr. John C. Mather. Northrop Grumman Space Technology serves as the primary contractor for the development and integration of the observatory. They are responsible for developing and building the spacecraft, which includes both the spacecraft bus and sunshield. Ball Aerospace has been subcontracted to develop and build the Optical Telescope Element (OTE). Goddard Space Flight Center is also responsible for providing the Integrated Science Instrument Module (ISIM).

The ISIM contains four science instruments. NIRCam (Near InfraRed Camera) is an infrared imager which will have a spectral coverage ranging from the edge of the visible (0.6 micrometres) through the near IR (5 micrometres). The NIRCam will also serve as the observatory's wavefront sensor, which is required for wavefront sensing and control activities. The NIRCam is being 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.

In addition to the near IR imaging capabilities of the NIRCam, the observatory will also perform spectrography over this range with the NIRSpec (Near InfraRed Spectrograph). NIRSpec is being built by the European Space Agency at ESTEC in Noordwijk, the Netherlands, leading a team involving Astrium GmbH, Ottobrunn and Friedrichshafen, Germany, and the Goddard Space Flight Center: the NIRSpec project scientist is Dr. Peter Jakobsen. The mid-IR wavelength range will be measured by the MIRI (Mid InfraRed Instrument), which contains both a mid-IR camera and spectrometer that has a spectral range extending from 5 to 27 micrometres. MIRI is being developed as a collaboration between NASA and a consortium of European countries, and is led by Dr. George Rieke (University of Arizona) and Dr. Gillian Wright (UK Astronomical Technology Centre, Edinburgh, part of the Particle Physics and Astronomy Research Council). The FGS (Fine Guidance Sensor), led by the Canadian Space Agency under project scientist Dr. John Hutchings (Dominion Astrophysical Observatory, Victoria), is used to stabilize the line-of-sight of the observatory during science observations and also includes a 'Tunable Filter module for astronomical narrow-band imaging in the 1.5 to 5 micrometre wavelength range. The infrared detectors for both the NIRCam and NIRSpec modules are being provided by the Imaging Division of Rockwell Scientific Company.