Its a bold promise, considering that NASA and the European Space Agency are still a dozen years away from even attempting a Terrestrial Planet Finder (TPF) that could barely see such worlds as tiny specks. Any talk of a planet imager is little more than idle speculation at this point.

One NASA concept envisions a spaceborne array of 20 telescopes, each 26 feet in diameter (akin to the largest ground-based mirrors today), separated by as much as 3,700 miles in space. Target date: Eventually. Price tag? Dont ask.

Labeyries EEI "hyper-telescope," as described in the September 17 Science, would also be a space interferometer, meaning that it would combine light gathered by widely separated, free-flying telescopes to simulate a single giant one. But the EEI would use many little mirrors instead of a few big ones, and would rely on a new technique called "densified pupil imaging" to get the most from the meager amount of light reflected from a distant planet.

Labeyrie figures he would need 150 telescopes, each 10 feet wide. These would be arranged in three concentric circles, with a baseline of 100 miles or so. That should be good enough, he says, to return snapshots 30 to 40 picture elements (pixels) wide of an Earth-size planet 10 light years away. By comparison, the Hubble Space Telescopes best pictures of Pluto are only a few pixels across.

Caltech astronomer Charles Beichman, whos leading the science team for NASAs less ambitious planet finder, is intrigued but cautious. While the notion of resolving continents on distant Earths is still "pretty far out there," Labeyrie has produced "an imaginative new way to try to do it" that seems, at first glance, to be theoretically valid. And, says Beichman, "When Antoine comes up with something, its probably pretty good."

Study teams in Europe and the United States will take a close look at Labeyries proposal for a scaled-down, 36-telescope version called the Exo-Earth Discoverer to see if it can be adapted for the TPF design, he adds. But Beichman also feels obliged to point out the harsh realities of this business. Building and flying 150 spacecraft in ultra-precise formation is no cheap or easy task.

Undaunted, Labeyries observatory hopes to begin testing the principles of a hyper-telescope with a ground-based array called CARLINA sometime in the near future. And hell be rooting for a 2003 NASA mission called Space Technology 3, which aims to prove that small telescopes really can fly in formation and work together as an interferometer in space.