At the end of 2003, there were 2600 known Near Earth Asteroids (NEAs), and of these 691 are brighter than absolute magnitude H=18, which is taken to correspond to 1 km diameter. Of these, 131 are classed as PHAs (potentially hazardous asteroids) larger than 1 km. These data are from Alan Chamberlin and are posted on the JPL/NASA NEO Program Office website <http://neo.jpl.nasa.gov>. For comparison, there are estimated to be a total of 1100 +/- 100 NEAs larger than 1 km. Thus at the end of 2003 we had found 63 percent of these NEAs. Recently there appears to have been a modest slow-down in the discovery rate of NEAs larger than 1 km, perhaps reflecting the fact that we have already discovered nearly 2/3 of this population group. For the most recent three complete years (2001, 2002, and 2003), the numbers discovered are: 89, 95, and 67, respectively. We can check this effect by noting that the total discovery rate of all NEAs has not changed much, remaining at about 450/yr. Previously, improvements in the search systems more than compensated for the declining number of unknown asteroids bigger than 1 km waiting to be discovered. The Spaceguard Goal is 90 percent completeness by the end of 2008. This corresponds to discovery of 990 NEAs brighter than H=18 for the nominal population. The survey passed its halfway mark of 495 in mid-2000 (see News Archive note for 08/01/00). The 75 percent objective is 742 NEAs larger than 1 km. If we anticipate 50 discoveries during 2004, then the survey should reach this milestone at the end of this year. This leaves 4 more years to increase the number of known large NEAs from roughly 750 to 1000. To meet this goal, the current (2003) discovery rate of about 50/yr will need to be maintained by improvements in the system to compensate for a shrinking pool of undiscovered objects. Stay tuned to see if this is accomplished. The 2003 NASA study of sub-kilometer NEAS (News Archive for 12/01/03) focused on PHAs rather than NEAs. The estimated population of PHAs larger than 1 km is 258 (from the NASA SDT Report, pg 21), leading to a reformulated Spaceguard Goal of discovering 232 large PHAs by the end of 2008. The number of 131 PHAs (discovered as of the end of 2003) is 56 percent of the way to meeting the Spaceguard goal. Please note that conversions between NEAs and PHAs, as well as the total numbers above the 1 km size, vary because the assumptions about such things as the conversion from magnitude to diameter are not exactly the same in different studies. The Spaceguard Survey is healthy and continuing toward meeting its 90 percent goal sometime between 2008 and 2010. However, the discovery rate of large NEAs has apparently gone through its peak, based on current survey systems. Larger aperture survey telescopes now under design (at Lowell Observatory and the University of Hawaii), of course, can be used to accelerate the discovery rate and push into the sub-kilometer size range (see stories below). COMING SOON: PAN-STARRS TO SEARCH FOR KILLER ASTEROIDS Honolulu Star-Bulletin, 25 April 2004 By Helen Altonn If one of the thousands of asteroids hurtling through space crashes into Earth, the damage could equal 700 Hiroshima-size bombs blasted at once. The potential danger of a collision with a 198-foot asteroid was pointed out recently to a U.S. Senate science committee by astronaut Ed Lu, who calls Honolulu one of his hometowns. He said there is a 10 percent chance of this happening. The first warning of a small killer asteroid could come from a special array of four small telescopes planned in Hawaii. The first telescope in the Panoramic Survey Telescope and Rapid Response System, called Pan-STARRS, is scheduled to be operating in two years on Haleakala, Maui, to test the system. "The project serves as a guardian," said Kenneth Chambers, of the University of Hawaii Institute for Astronomy. Chambers is principal scientist for the first prototype telescope. "We want to find them as far in the future as we can because it's much easier to do something about them," he said. The full telescope array will either be at Haleakala or Mauna Kea, on the Big Island, depending on environmental and site studies under way. When it is completed, the scientists expect to detect about 100,000 asteroids a month, said UH astronomer Nicholas Kaiser, principal investigator for the estimated $50 million Pan-STARRS project. "Most of those will be harmless," he said. "We're looking for the odd, bad one." Lu and astronaut Rusty Schweickart urged the Senate committee to use unmanned spacecraft to test methods of bumping an asteroid from an impact course with Earth. Lu said such capability could save the planet if space surveys warn of an approaching asteroid years in advance. That is the prime mission of Pan-STARRS, Chambers said, describing it as a "time machine." The goal is to find 99 percent of asteroids that could significantly damage Earth, determine their orbits and predict what they will do in 20 to 50 years, he said. The system will enable astronomers to detect objects as small as 330 yards in diameter and 100 times fainter than those observed by other telescopes. Instead of looking through telescopes to understand what happened in the past, Chambers said, astronomers will be looking at what will happen in the future. Repeatedly sweeping big patches of sky, he said, "we can find the ones that will be a threat in the future and those that will zoom by but are not going to do any harm, and only get worked up by those that are a threat." NASA's LINEAR survey project in New Mexico is concerned about asteroids about six-tenths of a mile in diameter and larger, which have the greatest potential for a catastrophic crash into Earth. It is believed one wiped out the dinosaurs 65 million years ago. The smaller ones that can be scrutinized by Pan-STARRS "are less hazardous and less massive, but there are a hell of a lot more of them," Kaiser said. "If they're under 300 meters," said Chambers, "they may wipe out a city or cause a tidal wave, but we will not have mass extinction of the species or global climate change, what the big ones can and have done in the past and will do in the future." But Pan-STARRS is not just an asteroid hunter, Chambers said. It also will track other moving objects in space: stars, galaxies, planets, comets, supernova and gamma-ray bursters. Covering the whole sky night after night "will provide a movie not only of our solar system, but of our galaxy and of our universe," Chambers said. This will give astronomers predictive capability "even out to cosmological scales," he said. "We'll be able to measure the geometry of the universe and the fate of the universe, as well." The Air Force has provided $20 million to build the first telescope, expected to be in operation by Jan. 1, 2006. Money is being requested for the other three, Kaiser said. He said they hope to put one up every six months so the full array will be operational by the end of 2007. NASA's Lunar Ranging Facility is being phased out on Haleakala, and Pan-STARRS will use the existing building with some modifications, Kaiser said. He said Pan-STARRS will be the most powerful instrument by far for any astronomy that requires rapid imaging of large patches of the sky over and over again. Instead of one large mirror, each of the four telescopes, each nearly 6 feet in diameter, will have very large, state-of-the-art electronic cameras with extremely fine resolution of 1 billion pixels. The full array will have 4 billion pixels. The most powerful survey instrument now is 300 million pixels at the Canada-France-Hawaii Telescope on Mauna Kea, Kaiser said. A pixel is the smallest element of a digital image. Its field of view is 1 square degree, he said, noting the moon's diameter is half a degree. Pan-STARRS will cover 7 square degrees of sky at once -- 40 times the area of the full moon, Kaiser said. "This is what we've got to do to catch asteroids, to scan thousands of degrees every night. ... They're a moving target," he said. Chambers said Pan-STARRS is innovating camera, computer and telescope technology. "The camera itself would be considered a supercomputer only a few years ago," he said. UH astronomers acquiring patents for leading-edge technology are John Tonry, who invented the detector device, and Klaus-Werner Hodapp, who developed a method of obtaining more pristine data from the atmosphere. Kaiser said about 100 people are working on Pan-STARRS, including UH scientists and students. The Lincoln Laboratory at the Massachusetts Institute of Technology is building the detectors. Pan-STARRS is collaborating with the Maui High Performance Super Computer to process the unprecedented volume of data. But Chambers said the project will build a specialized supercomputer. "When the fire hose is turned on, we will be hit with the biggest data stream in history," he said, with about 3,000 gigabytes of data nightly. "We have to be able to push it through and reduce it at the end at the same rate it is coming in, so we're on the forefront of computer technology to do that," Chambers said. He said a large number of small, cheap computers will be connected with innovative software to take the raw data from the sky and process it at once. Kaiser said a spinoff application of the telescopes is to detect transient things like gamma-ray bursts, the brightest objects in the cosmos, and process the data within minutes to alert bigger telescopes to follow up on them. "Ultimately," Chambers said, "the images that will come out of this will be so spectacular ... it boggles the mind. "When we do an IMAX fly-through the universe, that will be pretty amazing." Aside from pioneering astronomy, he said the Air Force is providing money through Pan-STARRS to relocate the TV broadcast towers on Haleakala because the transmissions would interfere with the telescope. The broadcast stations are collaborating with the project, and the antenna site will be restored, he said. Pan-STARRS also will provide cultural training for everyone who works on the mountain, from construction crews to scientists, "so they know how to behave and respect the mountain," Chambers said. "At the end of the project, the mountain will be in better shape than it is today, and the planet will be safe." LOWELL OBSERVATORY AND DISCOVERY COMMUNICATIONS, INC., ANNOUNCE PARTNERSHIP TO BUILD INNOVATIVE TELESCOPE TECHNOLOGY Press Release, October 15, 2003 Flagstaff, Ariz. - Today, Lowell Observatory and Discovery Communications, Inc., announced their collaboration to build a $30 million telescope that will significantly impact the exploration of our solar system and the universe beyond. The Discovery Channel Telescope (DCT) - designed exclusively for Lowell Observatory in Flagstaff, Ariz. - will be among the most sophisticated ground-based telescopes of its size. The four-meter telescope will have a significantly wider field of view than any currently existing telescope of its size, giving it the unprecedented ability to survey the sky at nearly eight times the capacity of the largest existing survey telescope. In this wide-field mode, the DCT's ability to perform deep imaging surveys of the night sky will be unmatched. This versatile telescope can be quickly converted to its alternative optical configuration, allowing it, unlike other pure survey telescopes, to be highly effective during bright phases of the moon. Once operational, the DCT also will have real-time capability, allowing the images acquired by the telescope to be simultaneously broadcast to people around the world. "Since its founding more than a century ago, Lowell Observatory has been dedicated to astronomical research, particularly the study of our solar system and its evolution, and to sharing that knowledge with the public," said Robert L. Millis, director of the observatory. "The Discovery Channel Telescope will have a considerable impact on the exploration of our solar system and the deep reaches of space, and we are very excited to be working in partnership with Discovery Communications to develop this innovative technology." Millis also noted that the partnership with Discovery Communications, Inc., which also includes educational programming and Lowell Observatory's involvement in Discovery's annual Young Scientists Challenge, was a natural fit given the Lowell's research and educational mission and the founding principles of the education and discovery-oriented company. "Discovery Communications was founded to provide the highest-quality television in the world enabling people to explore their world and satisfy their natural curiosity," said John S. Hendricks, founder, chairman and CEO of Discovery Communications, Inc. "Together, Discovery and Lowell Observatory will literally explore our world and bring the most exciting new discoveries found in our universe to millions of people around the globe." Among the DCT's numerous scientific objectives, the search for near-Earth asteroids, Kuiper Belt Objects and planets orbiting other stars, will be substantially advanced. Approximately 2,300 near-Earth asteroids have been discovered in the last decade. Once complete, the DCT will make it possible to identify the same number of potentially life-threatening near-Earth asteroids in just 30 days. The DCT also will make it possible to identify smaller near-Earth asteroids capable of causing regional devastation. Currently, the federally mandated search for near-Earth asteroids focuses on objects that are larger than a kilometer in diameter and capable of creating global devastation. Similar results are expected in the search for Kuiper Belt Objects, of which only 863 have been identified and can range in size from that of large asteroids to objects comparable in size to the planet Pluto. The Kuiper Belt, the first objects of which were discovered in 1992, is a sun-centered swarm of orbiting icy bodies extending from Neptune to as yet unknown distances. Construction is expected to begin on the DCT in fall 2004, with completion in 2008. The telescope's innovative components are already in design and production. The DCT's mirror blanks are being developed by Corning Incorporated in Canton, N.Y. Design currently continues on the following telescope components: optical system by Goodrich Corporation in Danbury, Conn.; facility and site design by M3 Engineering in Tucson, Ariz.; and the telescope mount by Vertex RSI in Richardson, Texas. The camera that Lowell will design and build for the four-meter telescope will have 36 2K by 4K charge-coupled devices capable of acquiring enormous amounts of data from each exposure and has a two degree field of view. |
