James Webb Space Telescope

The James Webb Space Telescope (JWST) is a large, infrared space telescope with a 6.5-meter primary mirror. The planned launch date is 2013 and will serve thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.

JWST will find the first galaxies that formed in the early Universe, connecting the Big Bang to our own Milky Way Galaxy. JWST will peer through dusty clouds to see stars forming planetary systems, connecting the Milky Way to our own Solar System. JWST's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range.

JWST will have a large mirror, 6.5 meters (21.3 feet) in diameter and a sunshield the size of a tennis court. Both the mirror and sunshade won't fit onto the rocket fully open, so both will fold up and open only once JWST is in outer space. JWST will reside in an orbit about 1.5 million km (1 million miles) from the Earth.

About

The James Webb Telescope is an international collaboration between NASA, the European Space Agency and the Canadian Space Agency. The NASA Goddard Space Flight Center is managing the development effort. The prime contractor is Northrop Grumman Space Technologies. The Space Telescope Science Institute will operate JWST after launch.

Several innovative technologies have been developed for JWST. These include:

1. Folding segmented primary mirror - adjusted to shape after launch
2. Ultra-lightweight beryllium optics
3. Detectors able to record extremely weak signals
4. Microshutters that enable programmable object selection for the spectrograph
5. A cryocooler for cooling the mid-IR detectors to 7K.

Mission

The JWST's primary scientific mission has four main components:

1. To search for light from the first stars and galaxies which formed in the Universe after the Big Bang

2. To study the formation and evolution of galaxies

3. To understand the formation of stars and planetary systems

4. To study planetary systems and the origins of life.

The telescope's launch is planned for no earlier than June 2013. It will be launched on an Ariane 5 rocket into an L2 orbit with a launch mass of approximately 6.2 t. 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.

Instruments:

JWST's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range. It will be sensitive to light from 0.6 to 27 micrometers in wavelength.

There will be four science instruments on JWST:

1. NIRCam (Near Infrared Camera)

NIRCam is an infrared imager which will have a spectral coverage ranging from the edge of the visible (0.6 micrometres) through the near Inradred (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.

2. NIRSpec: (Near Infrared Spectrograph)

NIRSpec enables scientists to obtain simultaneous spectra of more than 100 objects in a 9-square-arcminute field of view. This instrument provides medium-resolution spectroscopy over a wavelength range of 1 to 5 micrometers and lower-resolution spectroscopy from 0.6 to 5 micrometers. The NIRSpec employs a micro-electromechanical system "micro-shutter array" for aperture control, and it has two HgCdTe detector arrays.

NIRSpec is being built by ESA 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 infrared detectors for both the NIRCam and NIRSpec modules are being provided by Teledyne Imaging Sensors (formerly Rockwell Scientific Company).

3. MIRI: (Mid Infrared Instrument),

MIRI contains both a mid-infrared camera and spectrometer that has a spectral range extending from 5 to 27 micrometres, with a possible spectrographic coverage up to 29 micrometers. MIRI is being developed in collaboration between NASA and a consortium of European countries and is led by Dr. George Rieke (University of Arizona) and Dr Gillian Wright (UK Astronomy Technology Centre, Edinburgh).

4. FGS: (Fine Guidance Sensor)

FGS is a very broadband guide camera that is incorporated into the cryogenic instrument payload in order to meet the image motion requirements of the JWST. This sensor is used for both "guide star" acquisition and fine pointing. The sensor operates over a wavelength range of 1 to 5 micrometers. It will be used to stabilize the line of sight of the observatory during science observations and also includes a Tunable Filter Imager module for astronomical narrow-band imaging in the 1.5 to 5 micrometre wavelength range.

The FGS (Fine Guidance Sensor) is led by the Canadian Space Agency under project scientist Dr John Hutchings (Dominion Astrophysical Observatory, Victoria).

The Fine Guidance Sensor Tunable Filter Camera is a wide-field, narrow-band camera that provides imagery over a wavelength range of 1.6 to 4.9 micrometers, with a gap between 2.6 and 3.1 micrometers, via tunable Fabry-Perot etalons that are configured to illuminate the detector array with a single order of interference at a user-selected wavelength. The camera has a single HgCdTe detector array.

NASA has also been considering adding a grapple feature so future spacecraft might visit the observatory to fix gross deployment problems, such as a stuck solar panel or antenna. However, the telescope itself would not be serviceable, so that astronauts would not be able to do things such as swapping out instruments, as has been done with the Hubble Telescope.

History

JWST was formerly known as the Next Generation Space Telescope (NGST). JWST was renamed in September 2002 after NASA's second administrator, James E. Webb.

26 June 2007: JWST Full-Scale Model Visits Dublin, Ireland.

6 June 2007: NASA and ESA Sign Agreements for Future Cooperation on JWST and LISA missions.

26 June 2007: Extra-Solar Planet Exhibition Unveiled at Goddard Visitor Center. Worlds Beyond was organized by the National Space Society in partnership with the James Webb Space Telescope's education effort at Goddard.

14 June 2007: Construction Begins on the JWST's Guidance Sensor and Imager.

Specs and Info:

Wavelength: Infrared
Location: L2 Lagrangian point
Diameter: 6.5m
Collection Area: 25m²
Orbit Period: 1 Year
Focal Length: 131.4 m (431.1 ft)

Operate at Infrared Wavelengths

Due to a combination of redshift, dust obscuration and the 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 kelvin (−220 °C, −370 °F).

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.

Cost History

In April 2006 the program was independently reviewed following a replanning phase which began in August 2005 due to costs growth. The review concluded the program was technically sound, but that funding phasing at NASA needed to be changed. NASA rephased its JWST budgets accordingly.

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 2007 the cost of the project was estimated at about US$ 4.5 billion.

Builders, Construction and engineering

NASA's Goddard Space Flight Center in Greenbelt, Maryland is leading the management of the observatory project. The project scientist is Dr John C. Mather. Northrop Grumman Space Technology serves as the primary contractor for the development and integration of the observatory and are responsible for developing and building the spacecraft element, 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).

Did you know?

* JWST has a planned mass half that of the Hubble Space Telescope.

* The James Webb Space Telescope (JWST) is a planned space infrared observatory, intended to be a significant improvement on the aging Hubble Space Telescope.

* A model of the telescope has been on display at various places since 2005: Seattle, WA; Colorado Springs, CO; Paris, France; Greenbelt, MD; Rochester, NY; Orlando, Florida and Dublin, Ireland (June 2007). The model was built by the main contractor, Northrop Grumman.

Related Books:

Planet Quest: The Epic Discovery of Alien Solar Systems by Ken Croswell
From Amazon.com

Distant Wanderers: The Search for Planets Beyond the Solar System by Bruce Dorminey
From Amazon.com

James Webb Space Telescope Links:

The James Webb Space Telescope: NASA

Reference:

Picture of James Webb Space Telescope: 11/8/2007