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Asteroid deflection
NASA is planning missions to study how to divert a threatening asteroid, including an experiment known as DART, or Double Asteroid Redirection Test. (NASA Illustration)

The White House has issued an updated plan that lays out the roles played by NASA and other federal agencies in anticipating threats from near-Earth objects — and makes clear that if a threat arises, America will address it alone if need be to protect its national interests.

The latest edition of the National Near-Earth Object Preparedness Plan lists steps to be taken over the next 10 years to heighten U.S. capabilities to respond to potentially threatening asteroids and comets.

For now, the top priority is to detect and keep track of near-Earth objects, or NEOs, with NASA’s Near-Earth Object Observation Program playing the lead role.

NASA has already achieved one congressionally mandated objective — to detect more than 90 percent of the NEOs wider than 1 kilometer (0.6 miles). Such objects have the potential to cause mass extinctions on a scale similar to the blast that killed off the dinosaurs 65 million years ago.

But the agency has fallen short in its progress on a follow-up objective, to detect 90 percent of the NEOs with diameters in excess of 140 meters (460 feet), which are considered “city-killers” capable of wreaking regional destruction.

“Our best estimate of that size population shows that about two-thirds remain to be found,” Lindley Johnson, NASA’s planetary defense officer, told journalists today.

Looking ahead, Johnson said he expected the search to be expanded to look for NEOs as little as 50 meters (164 feet) across.

The preparedness plan calls for boosting NEO-detecting capabilities, through ground-based telescope programs such as the yet-to-be-completed Large Synoptic Survey Telescope in Chile as well as space-based observing platforms.

NASA has been considering a space mission known as NEOCam to help fill the gap. Johnson said some of the questions surrounding the mission, such as the performance of its infrared camera system how to deal with what’s expected to be a flood of data, had to be resolved before NASA makes a decision on whether to launch NEOCam.

The federal government aims to boost NASA’s funding for asteroid detection and mitigation to $150 million next year. A significant chunk of that money will go toward preparations for a robotic mission called the Double Asteroid Redirection Test, or DART, Johnson said.

DART, due for launch in 2020, is designed to study how smashing into a NEO can redirect its path. For DART, the target is a binary near-Earth asteroid called Didymos. Johnson said such a kinetic impact could conceivably be used in the future to deflect an asteroid from a threatening path.

At least two other deflection strategies are receiving serious consideration.

If the potentially threatening asteroid is no bigger than about 100 meters, and if astronomers can provide several years’ advance notice, NASA could send a “gravity tractor” to take up a position nearby. Over time, the probe’s gravitational pull could nudge the asteroid onto a less threatening path. “That technique could be enhanced if the spacecraft could collect some mass from the surface,” such as a large boulder, Johnson said.

If the object is larger, or if there’s less notice, a nuclear device might have to be exploded next to the NEO. The aim wouldn’t necessarily be to break up the object, Johnson said. Instead, the blast would blow off material and create a “rocket push against the asteroid to divert it,” he said.

NASA isn’t the only federal agency thinking about the asteroid threat: Two years ago, the White House set up an interagency working group for detecting and mitigating the impact of Earth-bound near-Earth objects, or DAMIEN.

DAMIEN’s members include representatives from the Defense Department and the Federal Emergency Management Agency.

Leviticus Lewis, chief of FEMA’s National Response Coordination Branch, noted that NEO impacts are low-probability, high-consequence events — which adds to the challenge for emergency preparedness officials.

Lewis said his agency has conducted three tabletop exercises so far to give officials a sense of what an asteroid threat might involve.

“For emergency managers, this is so different we have to first educate them on why this is different,” he said. “For instance, everybody in America knows what a hurricane curve looks like, or the error cone. But if we show impact possibilities from an asteroid, most emergency managers would have no idea what that means, or how NASA even came up with this information.”

Johnson said the ideal would be to provide up to a decade’s worth of warning about a NEO impact, but he acknowledged that there could be far less advance notice.

“Even a short warning on the order of days or weeks is still valuable,” he said. “It gives us enough time to evacuate an area where the impact may occur.”

So, who has the ultimate say on addressing the threat, and launching the nukes if necessary?

The preparedness plan notes that NASA is part of the International Asteroid Warning Network, a U.N.-backed organization that focuses on collection and rapid reporting of asteroid sightings. NASA is also a member of the U.N.-mandated Space Mission Planning Advisory Group, which would make recommendations on responses to a NEO threat.

But don’t expect the United States to stand back if the United Nations dithers.

“While international cooperation is the most effective way to manage NEO impact risks, the United States should also be prepared to act independently through all phases that may occur during an impact scenario to protect and preserve America’s interests,” the plan says.

And don’t expect astronauts to wrangle a wayward NEO, the way they do in movies like “Armageddon” or “Deep Impact.”

“It makes a good movie, but we do not see in our study any technique that would require the involvement of astronauts,” Johnson said. “Our studies just don’t show that that is a needed element.”

For details, check out the Trump administration’s NEO preparedness plan and compare it with the Obama administration’s preparedness plan. And stay tuned for Asteroid Day, an annual consciousness-raising event on June 30.

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