Leaders of the nonprofit B612 Foundation today took the wraps off a campaign to fund and launch a space telescope to hunt for potential killer asteroids — a campaign they portrayed as a cosmic civic improvement project.

Former NASA astronaut Ed Lu, the foundation's chairman and CEO, estimated that hundreds of millions of dollars would have to be raised to fund the project, but said he was "confident we can do this."

"We've been at this particular project for a year now," Lu told me in advance of today's campaign kickoff at the California Academy of Sciences' Morrison Planetarium in San Francisco. "We have people who are internationally well-connected, and we have a message that we think resonates with people ranging from large donors to perhaps half a million kids worldwide."

The foundation's aim is to identify and map the orbits of half a million asteroids that are on trajectories approaching Earth over the course of five and a half years, using a spacecraft that's launched into a Venus-type orbit on a SpaceX Falcon 9 rocket in the 2017-2018 time frame.

Apollo astronaut Rusty Schweickart, B612's chairman emeritus, said the task could be key to humanity's long-term survival. "We feel a certain urgency to get on with it so that we can be confident that we're not going to have a cosmic disaster here for no good, justifiable reason, just because we didn't get with it," he said in a statement. "So let's get with it. That's the name of the game."

What's the risk?
The potential risk posed by near-Earth asteroids was highlighted earlier this month when a kilometer-wide (0.6-mile-wide) asteroid called 2012 LZ1 sailed within 3.3 million miles (5.3 million kilometers) of our planet, just a few days after its discovery. If a rock that big were to hit Earth, it could end civilization as we know it. Smaller asteroids, around 40 meters (130 feet) in diameter, could set off atom-bomb-scale explosions like the 1908 Tunguska impact, which flattened 500,000 acres (2,000 square kilometers) of forest in Siberia.

Ground-based telescopes and space probes such as the NASA's now-defunct Wide-field Infrared Survey Explorer have found thousands of near-Earth asteroids, including an estimated 90 percent of the planet-killers measuring a kilometer or more wide. But there are hundreds of thousands more yet to be found in the Tunguska-or-bigger range.

The B612 Foundation, which takes its name from the asteroid that was home to the main character in a children's book titled "The Little Prince," was formed in 2002 to advocate strategies for deflecting potentially hazardous asteroids. A little more than a year ago, the foundation decided to shift its focus to mapping the inner solar system.

"Over the years it became clear that deflecting asteroids is a solvable technical problem as long as there is adequate early warning (decades of notice)," the foundation said in a briefing paper. "It also became clear that the job of tracking asteroids to provide early warning was not going to be accomplished by others in a timely fashion."

What's the mission?
To track more asteroids, the foundation proposes launching the Sentinel Space Telescope, a 1.5-ton, 25-foot-tall (7.7-meter-tall) observatory that draws upon design features from NASA's Spitzer Space Telescope and Kepler planet-hunting probe. Ball Aerospace was involved in both those earlier space projects, and would be the prime contractor for the Sentinel. The craft would carry a 20-inch (50-centimeter) telescope with an infrared imager.

Lu said the telescope's design has been nearly completed under the leadership of mission director Harold Reitsema, an astronomer who recently retired from Ball Aerospace. Negotiations are currently under way with Ball Aerospace on a fixed-price contract to build the Sentinel, Lu said. He declined to be specific on the mission cost because of those negotiations.

The mission plan calls for the craft to be launched on a Falcon 9 into a slightly elliptical orbit between Earth and Venus. From that vantage point, the Sentinel could look out toward the vicinity of Earth's orbit with the sun behind it — which would be ideal for spotting space rocks like 2012 LZ1. Image data would be beamed down to NASA's Deep Space Network and passed along to the mission's data operations center at the Laboratory for Space Physics in Boulder, Colo. Newly identified asteroids would be reported to the International Astronomical Union's Minor Planet Center, in accordance with existing procedures, and the orbital data would be analyzed by NASA's Jet Propulsion Laboratory to assess potential hazards.

The B612 Foundation said it signed a Space Act Agreement with NASA on June 19 in support of the mission. The foundation has also been in contact with SpaceX's engineers to discuss technical details for the anticipated launch, Lu said.

B612 Foundation / Ball Aerospace

Schematics show how the Sentinel Space Telescope would be put together.

B612 Foundation / Ball Aerospace

The Sentinel Space Telescope would take up a Venus-type orbit and look outward toward Earth's orbit.

What are the chances?
The fund-raising challenge could be as daunting as the challenges associated with spacecraft development. But Lu said the success of SpaceX's commercial resupply mission last month boosted his confidence that a non-governmental space effort could be successful. After his 2007 retirement from NASA's astronaut corps, Lu worked for three years as a Google executive, and he was inspired to go forward with the Sentinel project when he returned to Google's Silicon Valley headquarters to give a talk.

"I told them the essential problem was that nobody is mapping the asteroids," he recalled. "One of the guys there said, 'Why don't you just go and do it?' ... And then we said, 'Hey, maybe we can.' It was eye-opening to me to see how commonplace these types of fund-raising projects are."

Lu pointed out that the estimated cost of the mission, amounting to a few hundred million dollars, was comparable to the cost of building a performing arts center, a museum, or a planetarium like the one where today's briefing was being held. The San Francisco Museum of Modern Art, for example, has raised more than $437 million in its current capital campaign. "There are 50 to 100 projects larger than ours going on at any time in the United States, and nobody bats an eye," he said.

He also recalled that many of the world's best-known observatories, including the Palomar Observatory, the Lick Observatory and the Keck Observatory, were built with private financing. "I think of this as following in the precedent of large ground-based telescopes, from a funding standpoint," Lu said. 

It would be nearly unprecedented, however, to mount a space mission exclusively with private donations. The nonprofit Planetary Society and Cosmos Studios tried to do so in 2005 when they financed the launch of the Cosmos 1 solar sail on a Russian submarine missile — but that $4 million mission failed, and the follow-up LightSail 1 mission has not yet been launched.

NASA looked into launching an asteroid-hunting probe years ago, but never went forward with the mission because it was deemed too expensive. The cost was estimated at $500 million nine years ago, Tim Spahr, director of the Minor Planet Center, told The Associated Press.

Spahr questioned whether enough could be raised for the Sentinel project, given the state of the economy. "This is a hard time," he told AP.

The B612 Foundation's list of directors and advisers include some well-known names in the fields of fund-raising and venture capital, such as Dick Bingham, Geoff Baehr, Esther Dyson, Alexander Galitsky and Steve Jurvetson. Other members of the "B612 Founders Circle" include Google senior vice president Alan Eustace, Broadcom President/CEO Scott McGregor and Reddit CEO Yishan Wong. In the end, fund-raising power may be as essential for the Sentinel's successful liftoff as SpaceX's Falcon 9 rocket.

Update for 9:50 p.m. ET: During a follow-up news briefing, a few more nuggets about the Sentinel project came to light:

• B612's aim is to find 90 percent of the Earth-orbit-crossing asteroids that are at least 460 feet (140 meters) wide, and 50 percent of the Tunguska-type asteroids that are 130 feet (40 meters) wide. Reitsema said an internal analysis indicates that such a feat would be doable during a 5.5-year mission. Lu said an independent technical review panel headed by former JPL flight manager Tom Gavin would monitor the Sentinel Space Telescope's development to make sure it does what it's intended to.
• No money is changing hands under the terms of the agreement that B612 has with NASA, and the foundation will make the orbital data on asteroids freely available via the channels provided by the Minor Planet Center and JPL's Near Earth Object Program Office. However, B612 and NASA will have a six-month exclusive proprietary interest in scientific publications based on the data. Lu said that NASA is looking into funding a science team to make use of the Sentinel data. "We expect to make some more announcements in the near future on that," he said.
• Schweickart said that B612's effort was complementary to Planetary Resources' previously announced plan to identify and mine near-Earth asteroids, but that the two groups were not working together. B612's main objective is to map asteroids astrometrically and comprehensively, but not determine their composition or value for exploitation. Planetary Resources is mainly interested in identifying asteroids that have the right stuff for mining, such as water ice or precious metals.  
• If an asteroid is found to pose a collision threat, Lu expects that his "gravity tractor" concept would be considered for diverting the asteroid. However, that strategy takes time. "A few decades makes these things reasonable ... but when you are getting down under a decade or so, it can become very difficult in any case."
• Now that we know what we know about potentially hazardous asteroids, Lu said that there's an imperative to do something about them. "I think it would be embarrassing if we were to be struck by a major asteroid in the next few decades, simply because we didn't choose to do the mapping that's needed to find these asteroids," he said. If that were to happen, "shame on us," he said.
• Lu noted that most projects of this scale end up with the resulting facility being named after the project's principal benefactor — for example, the W.M. Keck Observatory. "Hint, hint," Schweickart interjected. Want to have a space telescope named after you? Hundreds of millions of dollars should do the trick. 

More about asteroids:

• Asteroid experts plan space telescope
• How to handle asteroid threats
• Asteroid debate rises to next level
• Asteroid likely to spare Earth in 2040
• Reality check for asteroid miners
• Interactive: Close encounters of the asteroid kind
• Cosmic Log archive on asteroids

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.