PASADENA, Calif. NASAs Jet Propulsion Laboratory (JPL) announced Tuesday it has awarded its first contracts to begin design work on a highflying quartet of telescope-equipped satellites that will seek out other Earth-like worlds.
The innovative Terrestrial Planet Finder mission, still more than a decade away from launch, will hunt for worlds like ours orbiting stars within a range of about 50 light-years, studying their numbers, size, location, diversity and suitability for life.
The missions initial design calls for four free-flying satellites, each carrying its own 137-inch (3.5-meter) infrared telescope in an Earth-trailing solar orbit. The light gathered by each telescope would be combined in a fifth satellite, which would also hold the missions instrumentation.
(NASA intends to test the concept in 2003 with the launch of Space Technology 3, made up of just two free-flying space telescopes that will fly and work in unison.)
The awards announced Tuesday went to Ball Aerospace, Lockheed Martin Space Systems, TRW and SVS Inc. The individual teams represent 75 scientists drawn from nearly 50 universities, industrial firms, research institutions and NASA centers.
"Weve succeeded in our goal of engaging some of the best minds in the world," said Firouz Naderi, the missions project manager at JPL, of the teams that will further refine various concepts for Planet Finder.
By December, NASA will narrow the field to two teams, which will then be subjected to further study ending in November 2001. The actual mission will not launch before 2012.
At the onset, the mission will examine some 250 stars already spotted by an earlier effort -- the Space Interferometry Mission set for launch in 2006 -- which will hopefully characterize any planets in orbit around them.
Once its cataloging work is complete, Planet Finder will then zero in on those stars that are most likely to hold habitable planets in an orbital embrace, searching for the telltale traces of life.
Through the technique of spectroscopy analyzing the spectrum of light reflected by the planets to see which elements are present the mission will tell scientists the relative proportions of gases such as carbon dioxide, water, ozone and methane at each of those planets. These elements can strongly suggest the presence of life.
"Well be looking for warm, water-bearing planets like Earth, and even for signs of primitive life," said Charles Beichman, the missions project scientist at JPL.
Scientists boast that the mission could, with as little as two weeks of observations, tell whether any particular planet harbors primitive life. The mission itself could last as long as five years.
To accomplish its task, the Planet Finder will wed the incredible sensitivity of spaceborne telescopes like the Hubble Space Telescope, but perhaps 100 times sharper with the high spatial resolution of an interferometer.
In interferometry, light gathered by separate telescopes is combined to form one image. However, the images resolution equals that produced by a telescope equipped with a single mirror as wide as the distance between the individual mirrors. In the case of the Terrestrial Planet Finder, the satellites will fly as far 0.6 miles (1 kilometer) apart.
The Planet Finder will take the "Goldilocks" approach in its search for habitable planets, using its four telescopes to focus on those bodies that are "just right" for life. That means the candidate planets must lie in a zone where temperatures allow for presence of liquid water, presumed to be necessary even for life beyond our planet.
To spot such small, relatively cool bodies, the Planet Finder will rely on a technique called "nulling" to block the bright glare of a planets parent star, allowing the dim planets to appear.
Since 1995, astronomers have discovered more than 30 planets orbiting stars other than our own. However, those planets have all been Jupiter-sized or larger, and far too close to their respective stars to be able to support life.
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