Asteroid Threat : Defending Our Planet from Deadly Near-earth Objects (9781616149147) (20 page)

Given what had turned up at Chicxulub—both literally and figuratively—it became clear that there was no higher priority
for Earth than defense against objects that could cause the ultimate catastrophe. The Alvarez team's discovery, which was a supremely important event in paleontology, was reported in an article they wrote that appeared in the June 6, 1980, issue of the respected and widely read journal
Science
. It started serious discussions in universities and in intellectual circles, generally about the extinction of the dinosaurs and many other creatures and about the large object that did them all in.
⁴
If the dinosaurs had had a space program, some in the aerospace community chortled, they would still be here. (They had an air force of pterodactyls, but it did not help.)

Congress eventually caught on and told NASA as much in the space agency's 1991 authorization bill. “The House Committee on Science and Technology believes that it is imperative that the detection rate of Earth-orbit-crossing asteroids must be increased substantially, and that the means to destroy or alter the orbits of asteroids when they do threaten collisions should be defined and agreed upon internationally. The chances of the Earth being struck by a large asteroid are extremely small, but because the consequences of such a collision are extremely large, the Committee believes it is only prudent to assess the nature of the threat and prepare to deal with it.”

NASA responded by issuing a Spaceguard Report in 1992 that laid out a plan for what would soon become known as the Spaceguard Survey, a comprehensive cataloging of all potentially dangerous NEOs. (Recall that, by then, the term
Spaceguard
, as used by Arthur C. Clarke in
Rendezvous with Rama
two decades earlier, had been cut in stone by the planetary-defense community as a suitably descriptive term for what was required.):

Impacts by Earth-approaching asteroids and comets pose a significant hazard to life and property. Although the annual probability of the Earth being struck by a large asteroid or comet is extremely small, the consequences of such a collision are so catastrophic that
it is prudent to assess the nature of the threat and prepare to deal with it. The first step in any program for the prevention or mitigation of impact catastrophes must involve a comprehensive search for Earth-crossing asteroids and comets and a detailed analysis of their orbits. Current technology permits us to discover and track nearly all asteroids or short-period comets larger than 1 km diameter that are potential Earth-impactors…. What is required…is a systematic survey that effectively monitors a large volume of space around our planet and detects these objects as their orbits repeatedly carry them through this volume of space…. The international survey program described in this report can be thought of as a modest investment to insure our planet against the ultimate catastrophe.
⁵

The document went on to describe in considerable detail what the space agency believed would be an adequate asteroid- and comet-surveillance program.

The Lowell Observatory in Flagstaff, Arizona, got into the NEO search in 1993 with funding from NASA, and it straightforwardly called the project the Lowell Observatory Near-Earth-Object Search. The facility is named for Percival Lowell, who founded it in 1894, and who was by all odds one of the most interesting characters in the history of American science. He was born in Cambridge, Massachusetts, in 1855, the scion of Brahmins who settled on the north shore of Cape Ann in 1639. He went to Harvard University, where he selected a challenging major: mathematics. It was a portent of the life that followed. Lowell was the personification of the Protestant ethic. He went on to become a businessman, a mathematician, an author, and an astronomer who titillated his colleagues by suggesting that there are canals on Mars that were built by an ancient civilization in a desperate attempt to survive. He also published a book,
Mars as the Abode of Life
, in 1908 that lent credence to the theory and undoubtedly helped H. G. Wells's
The War of the Worlds
, which was published ten years earlier, become an enduring work that spawned half a dozen feature films and an
infamous radio drama on the Columbia Broadcasting System's Mercury Theatre on the Air that aired on October 30, 1938—the infamous Halloween broadcast. In said broadcast, actor Orson Welles played a reporter who excitedly narrated the Martian attack with ray guns as if it were an actual news bulletin. Thousands of listeners in the northeastern United States and Canada who tuned in late thought it was real and became so terrified that they poured out of their homes and onto the streets to see the hideous invaders for themselves. The creatures ultimately evolved into those little green men in flying saucers who occasionally visited Earth, a myth that was dispelled when Mariners 4, 6, 7, and 9 and the two Viking spacecraft got to the Red Planet in the 1960s and '70s and found no canals, let alone ray-gun-wielding Martians.

The Lowell Observatory has observed more than five million asteroids, including 289 that were near Earth, fifty-nine of them declared to be potentially hazardous. It also discovered forty-two comets. On a night of good seeing, as astronomers call clear, dark nights with excellent visibility, the system could locate as many as six thousand asteroids, a few comets, and perhaps three or four new NEOs. During its fifteen-year life, which began in 1993 and ended in 2008, the Lowell Observatory Near-Earth Object Search (or LONEOS, as the observatory was called) made about 450,000 exposures in 130,000 regions of the sky. That turned into about fifteen terabytes of data, in the arcane argot of computerdom. Some idea of the magnitude can be gained by knowing that if those bytes of data were words instead of parts of images, they would fill twenty million three-hundred-page books, which is about thirty times the printed material in the Library of Congress. But thanks to the marvels of computer miniaturization, all of it can be stored in two suitcase-size server computers.
⁶

Whatever Tom Gehrels and Robert S. McMillan thought about
Tyrannosaurus rex
, pterodactyls, and other vanished
reptiles, they were astronomers in the University of Arizona's internationally respected Department of Astronomy and they were therefore well aware that asteroids and, to a far lesser extent, comets infest the neighborhood. And they certainly knew about what the Alvarez team discovered in the Yucatan. So they decided that the NEO “population” had to be meticulously studied and cataloged—inventoried—and that new computers could handle that task. Starting in 1984, Gehrels led a team of astronomers that used the large Newtonian telescope at the Steward Observatory on Kitt Peak, Arizona, to monitor every asteroid and comet they could find. They christened their project “Spacewatch.”

In 2001, Spacewatch began observing with a new telescope that had twice the aperture of the original one and that could therefore follow up on asteroids that become fainter after they are discovered. That gave them a more complete picture of asteroids' life cycles, which in turn helped to assess their danger. And to make matters even more interesting, since asteroids and comets are Solar System debris, the increased knowledge about them contributed to an understanding of how the Solar System was formed and how it works. Serendipity! McMillan was Spacewatch's principal investigator and went on to head the organization, which discovered some asteroids, perhaps most notably 20000 Varuna, an egg-shaped rock in the Kuiper Belt that some astronomers think is large enough to qualify as a dwarf planet. Like Kali, Varuna was named after a Hindu god, but this one a benevolent type who presided over the waters in heaven and was the guardian of immortality. Spacewatch's main contribution was not finding asteroids that came in close but in demonstrating the technology that was required to do it.
⁷

The Catalina Sky Survey watches “up over” as well as “down under,” which is to say it uses large telescopes on the peak of Mount Lemmon and on Mount Bigelow, both in the Tucson area, and one at Siding Spring Observatory in Australia.
Many of those who search the sky for NEOs and potentially hazardous asteroids (PHAs) are University of Arizona Wildcat Astronomers, whose offices and classrooms are nearby. The Catalina group has turned up more NEOs and PHAs than any other observatory, including Lincoln Near-Earth Asteroid Research (LINEAR), with 310 NEOs discovered in 2005, 396 in 2006, 466 in 2007, and 564 in 2008.

The Near-Earth Asteroid Tracking Program, which went by the public-relations-friendly acronym NEAT, did the same thing at the Jet Propulsion Laboratory (JPL) between 1995 and 2007, when it discovered thousands of asteroids using the US Air Force's advanced Ground-based Electro-Optical Deep Space Surveillance system on the Hawaiian island of Maui that was designed to scrutinize Soviet and other spacecraft during the Cold War. (The size of the antenna of a satellite that is positioned to intercept radio and other communication “traffic” on Earth gives a good indication of its capability, and the altitude of imaging reconnaissance satellites—spy satellites, as they are commonly called—provides an excellent clue as to what they are taking pictures of, since their altitude is lowered before their imaging systems are turned on and then raised after the “target” has been imaged. There are things to be learned just by knowing where a spacecraft is and what it looks like.)
⁸
It also used a large telescope at the Palomar Observatory in California. NEAT not only turned up thousands of new asteroids, but it also discovered or codiscovered several important comets. And whatever else it accomplished, NEAT had the distinction of being a contender for honors as a Great Acronym of Distinction (GAD), along with the American Indian Movement (AIM); Acquired Immune Deficiency Syndrome (AIDS); Zone Improvement Plan (ZIP-code); Near-Earth Asteroid Rendezvous (NEAR); and Light Amplification by Simulated Emission of Radiation (LASER).

Then came Sentinel, a decade-old concept that literally added a dimension to planetary defense by in effect stepping
way back and spotting NEOs in the infrared, so they stand out against the cold sky around them. The spacecraft's development was the brainchild of the B612 Foundation, and specifically of Russell L. “Rusty” Schweickart, Clark Chapman, Ed Lu, and Piet Hut. On Thursday morning, June 28, 2012, the foundation held a news conference at the California Academy of Sciences in San Francisco, at which it announced an important strategy for locating potentially hazardous asteroids. “The orbits of the inner Solar System where Earth lies are populated with a half million asteroids larger than the one that struck Tunguska, and yet we've identified and mapped only about one percent of these asteroids to date,” Lu, who had become chairman of the foundation, told journalists. The conference was called to announce the foundation's plan to build, launch, and operate Sentinel, the first privately funded spacecraft to go on a deep-space mission that, by definition, is far from Earth. The B612 Foundation estimated that the cost of developing and launching Sentinel would come to roughly $450 million.
⁹

The concept was not new, but its execution was. Instead of continuing to peer out from Earth in a necessarily narrow and limited field of vision to see what might be menacing it, or scanning the sky from a spacecraft orbiting Earth, B612 proposed to step very far back and see the big picture as it looks from a Venus-like orbit around the Sun. “We believe our goal of opening up the solar system and protecting humanity is one that will resonate worldwide,” Lu said. “We've garnered the support and advice of a number of individuals experienced with successive philanthropic capital campaigns of similar size or larger, and will continue to build our network. We've been given a gift, and the gift is that we have the ability now to go out there and actually do something which positively affects the future of humanity on Earth.”
¹⁰
A telescope in a Venus-like orbit would in fact not be efficient watching Earth's immediate neighborhood and would not see the planet at all half the time.

Sentinel's assignment is to locate 90 percent of asteroids 140 meters or larger in diameter that are in the inner Solar System and report what it finds. The foundation estimated that there are roughly half a million asteroids in the vicinity of this planet that are as large or larger than the one that exploded over Tunguska. The telescope, which will be made by Ball Aerospace and Technologies Corp. of Boulder, Colorado, will be 7.6 meters—twenty-five feet—long and will see in the infrared (again, so it can pick out relatively warm rocks against the very cold background of space). Sentinel is scheduled to be launched on a two-stage Falcon 9 rocket that was manufactured by the Space Exploration Technologies Corp., or SpaceX, a company in Hawthorne, California. SpaceX was started in 2002 by Elon Musk, a very imaginative entrepreneur and hyperactive inventor who has revived an old science fiction transportation mode for California: a so-called Hyperloop express train that would carry passengers across California at more than 1,200 kilometers an hour, making the ride from San Francisco to Los Angeles in a little more than half an hour. That's faster than by jetliner. And it would certainly reduce freeway congestion.
¹¹
Falcon 9 is a model for the kind of innovative and aggressive enterprise that is commercializing space after the shuttle's retirement. SpaceX also produced a partially reusable spacecraft called
Dragon
. The firm was awarded a $1.6 billion NASA contract in 2008 for twelve resupply flights to the International Space Station in which
Dragons
would be launched by Falcon 9s. The first one was successfully flown in October 2012. But the Sentinel mission stood to be of far greater importance where civilization's survival is concerned. Thus did the formidable founder of SpaceX become involved with B612 and planetary defense as well as all of his other lofty projects.

Pan-STARRS—for the Panoramic Survey Telescope and Rapid Response System—is an array of telescopes and astronomical cameras that survey the sky continuously and send what they
find to a central computing facility at the University of Hawaii's Institute for Astronomy (which, like the University of Arizona, is a veritable incubator of space watchers). It has financial support from an international consortium that includes Johns Hopkins and Harvard, with the US Air Force funding four 1.8-meter telescopes, the first of which began operating full-time at the summit of Haleakala on Maui in May 2010. Pan-STARRS's essential purpose is to spot asteroids and comets by comparing successive pictures so that anything that has moved stands out. The system was started as a collaboration between the Institute for Astronomy, LINEAR, the Maui High Performance Computing Center, and Science Applications International Corporation (better known as SAIC), the last of which is a defense contractor and think tank in Tysons Corner, Virginia. That location, uncoincidentally, puts it near CIA headquarters at McLean and on the same side of the Potomac as the Pentagon (and its procurement office).