Asteroid Threat : Defending Our Planet from Deadly Near-earth Objects (9781616149147) (21 page)

ATLAS, which is as venerable a name as there is in the English lexicon, stands for the Asteroid Terrestrial-impact Last Alert System Project—another neat…acronym—that is being developed at the University of Hawaii for use starting in 2015. All the scientists in the project have worked at Pan-STARRS, and ATLAS is intended to compliment it by searching “shallow but wide” sections of space rather than smaller “deep but narrow” portions of it with great magnification as Pan-STARRS does. The problem with Pan-STARRS, at least in the opinion of the ATLAS group, is that asteroids and comets can sometimes streak by while the telescopes are looking in a different direction. ATLAS is therefore designed to use as many as eight small telescopes with ten- to twenty-inch lenses at two or more locations to scan the entire visible dark sky twice a night. Ideally, its designers have said, it will operate in California and Arizona as well as in Hawaii. There are two advantages to spreading out the telescopes. Coverage at three locations will triangulate
asteroids and comets—see them from three directions—which will not only make fixing their positions more accurate but will also enable the system to see smaller NEOs than a one- or two-dimensional operation could. It will also allow the sky to be watched constantly so that clouds or storms will be far less likely to blind the system. Spaceguard actually covered that territory in its 1992 report, but duplication in planetary defense is an asset, not a sin.

John Tonry, the astronomer who heads ATLAS, compared its sensitivity to seeing a lighted match in New York from San Francisco. He of course knows that the object of planetary defense is to spot the object so far ahead of a collision that it can be diverted, but his group concentrates on the last-ditch scenario; on the asteroid or comet that is not a world-ender and that connects. The team predicts that there will be a week's warning time for fifty-meter “city-killers” and three weeks' warning time for 150-meter “county-killers.” The reaction plan that he describes brings chillingly to mind the civil-defense procedures that were put in place in case of a nuclear attack during the Cold War. “That's enough time to evacuate the area of people, take measures to protect buildings and other infrastructure, and be alert to a tsunami danger generated by ocean impacts,” he added.
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The Cold War analogy is not far-fetched. The project measures the impact threat the way the devastation caused by nuclear weapons is measured, so the “town-killers” are thirty kilotons, the “city-killers” are five megatons, and the “county-killers” are one hundred megatons. “Yes, these are the same kilotons and megatons of TNT used to describe nuclear explosions because a serious asteroid impact is very similar to a nuclear explosion, including a mushroom cloud, but without radioactivity or fallout,” the ATLAS group has explained. Ultimately, they want planetary defense to operate “robotically,” meaning automatically, and grow into a network that extends to the
Southern Hemisphere—Australia, Chile, or South Africa are mentioned—so there will be constant 'round-the-planet coverage. There would always be the biggest picture possible, in other words, and it would be a matter of staring at that picture all the time electronically to see what moves and, more to the point, what moves as a menacing potential impactor.

The Wide-field Infrared Survey Explorer, or WISE, as it is called by the planetary-defense fraternity, was another astronomical space telescope that was also designed to survey the sky in the infrared. It was launched into a polar orbit in mid-December 2009, and, by the following October, it had discovered more than 33,500 new asteroids and comets, including 136 near-Earth asteroids (NEAs), PHAs, and some comets that, typically, were not menacing. That is a tiny fraction of the roughly ten thousand that have been discovered by telescopes on terra firma. Nineteen of the PHAs were believed likely to hit Earth at some point and cause significant damage, in which case they will realize their potential unless they are stopped. That same month, the hydrogen coolant that kept the temperature of the telescope down was depleted, but the spacecraft had sent back so much data that it was rechristened NEOWISE, an evident play on NEO's two meanings—“near-Earth object” and “new”—and its mission was extended four months. The spacecraft then imaged roughly six hundred NEAs, leading its team to conclude that there are roughly 4,700 PHAs with diameters larger than one hundred meters that were relatively near Earth. The new observations also suggested that about twice as many PHAs are likely to be in lower inclination orbits, which are more aligned with Earth's orbit, than was previously thought.

“NASA's NEOWISE project, which wasn't originally planned to be part of WISE, has turned out to be a huge bonus,” Amy Mainzer, the mission's principal investigator at JPL, said. “Everything we can learn about these objects helps us understand their origins and fate. Our team was surprised to find
the over-abundance of low-inclination PHAs. Because they will tend to make more close approaches to Earth, these targets can provide the best opportunities for the next generation of human and robotic exploration,” she said in an apparent reference to landing a human or two on one of the larger boulders.
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Lindley Johnson, who studied NEOs intensively in the air force and then went to NASA, where he became the program executive for the Near-Earth Object Observation Program and a recognized expert in the field, agreed about the importance of extending WISE.

The NEOWISE analysis shows us we've made a good start at finding those objects that truly represent an impact hazard to Earth. But we've many more to find and it will take a concerted effort during the next couple of decades to find all of them that could do serious damage or be a mission destination in the future.

We think we've got a pretty good handle on anything that's large enough to cause global consequences. Our estimate is that we've found somewhat over 95 percent of those that are large. There's always going to be a few lurking out there in deep space that we will pick up as we continue the survey of the smaller objects. Our current objective is to find all the hazardous asteroids down to about 100 meters. That is a considerably more challenging mission than the one-kilometer size. We are still using the same telescopes that we used for the larger size mission because to date we have not gotten the funding to really be doing an adequate job for the smaller size missions. We have to have either a lot bigger telescopes on the ground for decades or you've got to get a space-based capability.
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Johnson's complaint was a familiar one in Washington. NASA's NEO program is so important that it warrants being a permanent, integrated, adequately funded operation, but its funding does not reflect that. “You've got to find them first. We're trying to design a program that will find them years in advance so that we do have time to do something about it. It's perfectly within our technical capability to be able to find all of those of a significant size that could have impact potential.
We've just got to do that.” But the effort lacks the funding to be as focused as it should be, he continued. “NASA's budget right now is well over-subscribed. We have a lot more on our plate to do than we have been given the budget to accomplish. This is something that you've got to anticipate well in advance and be looking at now to find an impactor that might occur in the second half of the century. It's the kind of lead time you prefer to have in dealing with something like this, particularly if it's a large object. We prefer to be able to intercept it years in advance and just give it a slight nudge and not have to worry about it.”

And, like in
The Little Prince
, Lindley Johnson thinks that asteroids have a good side as well as a bad one. “As we explore the Solar System and move out into it, how to live off the land, so to speak, will become important, and so mining asteroids, finding resources on them, certainly including water, will be important to our future in the Solar System.” He also stressed cooperation with the European Space Agency (ESA) and other foreign space organizations “to determine and then verify results before we make predictions.”
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International cooperation to protect the international community is a good deal less than it should be, but there are indications that it could strengthen. Although the United States leads the world by far in finding and cataloging asteroids and comets, threatening and otherwise, some other political entities have come to understand that since the danger is worldwide, so must be the response. Italy and Spain therefore started NEODyS, for Near-Earth Object Dynamic Site, in 1999. It is a program that calculates the orbits of asteroids and provides updated information on the Internet about where they are and where they are expected to be through 2100. The site is run by the University of Pisa. It's main feature is a risk page on which all NEOs that could theoretically hit Earth through the end of the next century are shown on the list, which grades them in five categories of probability, ranging from those that are lost
or are too small to worry about to those in a “special” category that are considered to be candidates for a possible impact (99942 Apophis is prominently included).

ESA started the Near-Earth Object Coordination Centre at the European Space Research Institute in Frascati, outside of Rome, on May 22, 2013. The centre operates under ESA's Space Situational Awareness Program, which began in 2009 and is developing an independent capability to watch for natural phenomena that could disrupt satellite operations in orbit or vital operations on Earth, such as power grids and communication. It consists of three main segments: monitoring conditions at the Sun, in the solar winds, and in Earth's space environment that can affect the planet's space- and ground-based infrastructure or endanger human life or health; watching for active and inactive satellites, spent launch stages that are in orbit, and all the space debris left over from the world's combined launches; and, last but by no means least, detecting NEOs that are potential impactors. So far, in common with other governmental agencies of all stripes the world over, it has not detected anywhere near the number of NEOs it has declared it wants to detect. It should be noted that the United Kingdom was only the second nation after the United States to endorse NEO surveys and planetary defense in an excellent 2000 parliamentary report.

The NEO Coordination Centre did have a clear triumph on June 26, 2013, though, when astronomers in several observatories spotted and sized up asteroid 2002 GT as it passed the planet at a distance of almost fifty times the distance to the Moon and coordinated what they saw. At that distance, 2002 GT posed no threat, but at a few hundred meters across, it made an excellent practice subject for any others in its size range that get closer. “The fly-by presented an ideal opportunity to exercise the unique coordinating function of ESA's new Near-Earth Object Coordination Centre,” Ettore Perozzi, the project leader for NEO services at Deimos Space, declared in
a tone of triumph that was somewhat exaggerated given the centre's record. “By alerting and then collating observations from diverse European teams, the Centre was able to provide a comprehensive set of results back to the scientific and space exploration communities, a cycle that wasn't happening before. This is really a first for Europe,” he proclaimed. The Spanish company operates a complete remote-sensing system with a satellite named Deimos-1. In keeping with the space community's penchant for dark humor, Deimos is the son of Ares and Aphrodite and the twin brother of Phobos in Greek myth. The name literally means “dread” and was the personification of the sheer terror that is brought on by war. The two moons that orbit Mars, which is itself named for the Roman god of war, are named Deimos and Phobos, and in an irony that Shakespeare would have savored, are thought to be captured asteroids.
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The far encounter with 2002 GT delighted astronomers and others in the space-science world because the asteroid is the intended target in a mission called Epoxi, in which a probe named Deep Impact, which was launched in 2005 (and which flew by and looked over comet Hartley 2 at close range and studied the composition of comet 9P/Tempel by sending an impactor into it) is supposed to intercept 2002 GT and scrutinize it, NASA's fragile budget permitting.

“Traditionally, Europe's asteroid community reliably delivered world-class observations and has been credited with many significant discoveries and findings,” Gerhard Drolshagen, the comanager of the NEO segment in the Space Situational Awareness Program said. “What was lacking, however, was a central point to coordinate and synthesize data that could function across national and organizational boundaries. Our centre has proven it can act as a driving force and a focal point for the European and international community involved in asteroid science, impact monitoring and mitigation.”
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Japan has its share of asteroid watchers (and worriers), too.
The Japan Spaceguard Association was established in 1996 to learn more about the threat, and what it learned convinced its members that they should be on the lookout for potential troublemakers, along with other nations that call themselves advanced. After long and arduous discussions with the government, the association finally won a concession to build an observatory at Bisei, a town in the low mountains of the Okayama Prefecture 150 kilometers west of Osaka. It was built in 1999 with funding from the Japan Aerospace Exploration Agency, is called the Bisei Spaceguard Center, and is the heart of the Japan Spaceguard Association. It claimed to have discovered more than one thousand asteroids, two of them NEOs, and a comet as of early February 2012.
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But the Japanese have been more than passive in addressing the situation. They have sent a probe to land on an asteroid, as the NEAR mission did, but with a very significant difference: it brought a sample home. The spacecraft was named Hayabusa (peregrine falcon) and was sent by the Japan Aerospace Exploration Agency to land on an asteroid named Itokawa in May 2003. It spent two and a half months flying with the rock and then landed on it in November 2005. Hayabusa not only sized up Itokawa pretty thoroughly, collecting data on its size, shape, spin, topography, color, mineral composition, density, and gravity, but it also picked up tiny grains of, well, asteroid and brought them home in June 2010.
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