TRW's design for the James Webb Space Telescope (formerly the Next Generation Space telescope). Prominently visible here are the blue sunshade which shadows the primary mirror and science instruments. The primamry mirror is expected to be at least 20 feet in diameter. Credit: NASA/TRW

NASA announced Tuesday that it has selected TRW to build a next generation space telescope that will replace the Hubble Space Telescope at the end of the decade.

NASA awarded TRW a $825-million contract to design and build the Next Generation Space Telescope, which will henceforth be known as the James Webb Space Telescope (JWST), after the late Apollo-era NASA administrator. The contract announcement, which had been expected since late August, was made early Tuesday morning.

While the JWST is billed as the successor to the Hubble - which is scheduled to be returned to Earth on a shuttle mission in 2010, the same year as the JWST is launched - the two telescopes are radically different, with the new telescope's design and location driven by scientific requirements that include studies of the origin of the universe and searches for other planetary systems.

In appearance the JWST will bear little resemblance to Hubble. The telescope's primary mirror will be approximately six meters in diameter, two and a half times wider than Hubble's main mirror. The large mirror will allow the telescope to detect objects 400 times fainter than Hubble can. Because no launch vehicle has a payload fairing wide enough to accommodate a single mirror that large, the JWST's mirror will be made of a number of hexagonal segments, folded up into a compact size for launch. Once in space the mirror will unfold into its full shape. A large rectangular sunshield, about the size of a tennis court, will also deploy after launch, protecting the mirror and other spacecraft components from the heat of the sun.

While Hubble was designed to observe in a wide range of wavelengths, from ultraviolet through visible light and into the infrared, the JWST will be optimized to look primarily in the infrared, although it will be able to observe in the visible as well. This is because many of the main science goals of the telescope, including the origin and structure of the universe as well as the formation of galaxies, require observing distant objects whose light has been redshifted into the infrared. In addition, studies of young stars and planetary systems, other key objectives of the telescope, are also best performed in the infrared. The telescope will have three instruments: a near-infrared camera, a near-infrared spectrograph, and a combined mid-infrared camera and spectrograph.

The choice of infrared observations requires putting the JWST in a different location than Hubble: if placed in Earth orbit, the planet's own infrared emissions would overwhelm any efforts by the telescope to detect faint signals from distant objects at similar wavelengths. Instead, the JWST will be launched on an expendable launch vehicle - most likely a version of the Delta 4 or Atlas 5 - to the Earth-Sun L2 Lagrange point, 1.5 million kilometers from the Earth in the direction opposite the Sun. From that location the spacecraft's sunshield will be able to block both sunlight as well as the Earth's infrared emissions.

The JWST will not be the first spacecraft to take advantage of the L2 point. NASA's Microwave Anisotropy Probe (MAP), a mission to map the cosmic microwave background left over from the Big Bang, is the first to use the gravitational point for scientific observations, entering orbit around it last year. ESA is planning to use L2 for several science missions, including Herschel, Planck, and Eddington, later this decade. The disadvantage of the L2 location is that spacecraft there, unlike Hubble, cannot be repaired or upgraded by shuttle crews.

The choice of the name of the telescope represents a departure from a NASA tradition to name astronomy spacecraft after famous astronomers, like Edwin Hubble. The JWST is named after James Webb, who was NASA's second administrator, running the agency from 1961 to 1968. While Webb is usually credited with overseeing the Apollo program, he also pushed for an ambitious program of robotic missions, including pioneering missions to the Moon, Venus, and Mars, as well as space-based astronomy endeavors.

"Thanks to his efforts, we got our first glimpses at the dramatic landscapes of outer space," Sean O'Keefe, the current NASA administrator, said of Webb. "He took our nation on its first voyages of exploration, turning our imagination into reality. Indeed, he laid the foundations at NASA for one of the most successful periods of astronomical discovery."

TRW beat out Lockheed Martin, the other finalist in the project, for the telescope contract. TRW also served as the prime contractor for Compton Gamma Ray Observatory and Chandra X-Ray Observatory, while Lockheed Martin is building the Space Infrared Telescope Facility (SIRTF), scheduled for launch next year, and was also involved in the development of Hubble.

The JWST contact is the latest in a series of wins for TRW, a company in the process of being acquired by Northrop Grumman. Last month TRW won a contract to develop a restructured version of the Space Based Infrared System (SBIRS) Low, a constellation of low-Earth orbit satellites designed to provide warning of missile launches. TRW also leads a team that won a contract last month to build a series of polar orbiting weather satellites that will serve both military and civilian agencies.

Video coverage for subscribers only:
   VIDEO: ANIMATION OF TELESCOPE DEPLOYING IN SPACE QT or RV
   VIDEO: INTERVIEW WITH THE PROJECT MANAGER QT or RV
   SUBSCRIBE NOW