The night sky

A former NASA astronaut — worried about asteroids smashing into Earth — is launching a crowd-funded effort to build a space telescope for spotting dangerous space rocks.

Plans are for the telescope, called Sentinel, to launch in 2017 or 2018, drift toward Venus and then spend 51/2 years surveying the inner solar system as it orbits the sun.

The telescope's unblinking eye will spot the warm glow of asteroids larger than about 100 feet across — large enough to destroy a city.

The mission is designed to give earthlings a head start of several years — or decades — to prepare a mission to deflect any threatening asteroids.

Spearheaded by Ed Lu, a physicist who flew on the space shuttle and the international space station, the project needs to raise "a few hundred million" dollars to get off the ground.

"This is crowdsourcing but on a grand level," he said.

While NASA spends some $5 million a year searching for big "planet killer" asteroids — and finding no such threats — no one has surveyed for smaller but still possibly catastrophic space rocks, Lu said.

"The chances were pretty minimal somebody else was going to do this," Lu said. "Federal budgets being what they are, it's just not going to happen."

The project's genesis reaches to 2001, when Lu joined with former Apollo astronaut Rusty Schweickart to start the nonprofit B612 Foundation. The group brought together scientists to draw up plans for how to deflect any asteroids headed toward Earth.

In the past year, Lu and the B612 Foundation — named after an asteroid in the 1943 French children's tale "The Little Prince" — have rounded up a who's who of space scientists, Silicon Valley entrepreneurs and venture capitalists to lead the campaign.

They've designed a telescope, tapped a company to build it — Ball Aerospace of Colorado, which has built other space telescopes — and signed an agreement with NASA to use the agency's radio dishes for communication.

Now they just need the money. The group is negotiating the final price with Ball.

The dropping cost of computers, telescope components and rocket launches made the project feasible, Lu said.

But another expert is skeptical that the telescope will cost just "a few hundred million" dollars. Tim Spahr of the Minor Planet Center in Cambridge, Mass., which tracks asteroids — and which would eventually analyze data from Sentinel — was part of a team that in 2003 proposed a similar mission to NASA. The cost of that unbuilt project: $400 million.

Spahr is also skeptical that Sentinel will spot every possible threat. "It is a spectacular challenge," he said. The telescope will miss some asteroids that take a long time to orbit the sun and will have to track each asteroid for "years" to determine whether it hit Earth, Spahr said.

Still, Lu is confident that his group can pull off the mission. "We'll be successful," he said.

And what will donors get for their contributions?

Said Lu: "You get to take part in saving the Earth."

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