Cosmic near misses hit the scientific bullseye


August 5, 1998


A NASA-sponsored asteroid tracking system has found two new large objects that cross Earth's orbital path, but show no signs of coming dangerously close to Earth within at least the next several decades, astronomers say.

The asteroids were found in observations made with the Near- Earth Asteroid Tracking (NEAT) system, managed by NASA's Jet Propulsion Laboratory, Pasadena, CA.

"These discoveries come on the heels of last month's installation of new state-of-the-art computing and data analysis hardware that speeds our search for near-Earth objects," said NEAT Project Manager Dr. Steven Pravdo of JPL. "This shows that our efforts to find near-Earth objects are paying off."

The newly discovered asteroids 1998 OH and 1998 OR2 are both large enough to cause global effects if one impacted Earth, and both are classified as "potentially hazardous objects" because they pass periodically near Earth's orbit (like at least 125 other objects discovered so far). Both asteroids are 1 to 3 kilometers (about 1 mile) in diameter.

Crucial follow-up observations of both asteroids made by co- investigator Dr. David L. Rabinowitz of JPL were used to calculate projected orbits that show that neither of the objects pose an immediate threat to Earth. Rabinowitz made the observations with the 61-centimeter (24-inch) telescope at the JPL's Table Mountain Facility in Wrightwood, CA, which is used to make immediate follow-up observations of recently discovered near-Earth objects in an effort to better determine their orbits and to compositions and rotational state.

"Our goal is to discover and track all the potentially dangerous asteroids and comets long before they are likely to approach Earth," said NEAT Principal Investigator Eleanor Helin. "The discovery of these two asteroids illustrates how NEAT is doing precisely what it is supposed to do."

Additional follow-up observations are required to more precisely determine the orbits of these asteroids, but preliminary projections show that 1998 OH can get no closer than about 5 million kilometers (about 3 million miles) -- about 20 times the distance between Earth and the Moon.

NEAT uses a large, sensitive and fully automated charge- coupled device (CCD) camera mounted on a 1-meter-diameter (39- inch) telescope operated by the U.S. Air Force at the 3,000-meter (9,000-foot) summit of Haleakela on the island of Maui in Hawaii. "Our upgraded equipment has speeded up the data processing allowing us to analyze up to 40 gigabytes of data each night, equivalent to 1,200 images of the sky," said Pravdo.

Images and other information about the new asteroids and the NEAT project can be found on the Internet at:


May 20, 1998


NASA astronomers conducting a monthly sweep of the night sky to identify previously unknown asteroids and comets will be able to double their coverage and the number of discoveries they make, thanks to new, state-of-the-art computer and data analysis hardware.

The new equipment was purchased with funds from NASA, which recently doubled its resources for near-Earth object research.

The new real-time analysis system, which serves a fully automated charged-couple device (CCD) camera and telescope atop Mt. Haleakala, Maui, HI, is part of the Near-Earth Asteroid Tracking (NEAT) project, based at NASA's Jet Propulsion Laboratory, Pasadena, CA. The new system features four 300- megahertz processors that will be devoted solely to the enormous amount of data coming back from the NEAT telescope on a nightly basis.

"This new system will speed up the processing of data and allow us to analyze up to 40 gigabytes of data each night, or the equivalent of nearly 70 CD-ROMs," said Dr. Steven Pravdo, NEAT project manager at JPL. "We will be able to double the amount of sky we search each night, which is currently 500 square degrees, as well as the number of new asteroids and comets we find during each monthly observation cycle."

Installed in 1995, the NEAT camera uses a very large, very sensitive 4,096- by 4,096-pixel CCD chip. The camera is located on a 1-meter-diameter (39-inch) telescope operated by the U.S. Air Force and located at an elevation of 3,000 meters (nearly 2 miles) above the Pacific Ocean. With stable climate, clear, dry air and little light pollution, the NEAT tracking system has been highly successful and continues to operate six days out of each month. With additional support, the project hopes to increase this six-day observational run to 18 nights of observations each month.

Asteroids are considered relics of the formation of the early solar system. Most of them are rocky materials, with some composed of nickel and iron. Most range in size from boulders up to the largest main belt asteroid, Ceres, which is approximately 965 kilometers (600 miles) in diameter. Comets, on the other hand, are bodies of ice with embedded rock and organic materials which heat up and become active, spewing gases and dust as they approach the Sun.

The NEAT telescope detects these small bodies by observing the same part of the sky three times during an interval of about one hour and comparing the three images to determine the location of objects moving across the sky. Since its inception, this fully automated system has detected more than 25,000 objects, including 30 near-Earth asteroids, two long-period comets and the unique 1996 PW, which has the most eccentric orbit of all objects discovered to date. More information about NEAT discoveries, along with black-and-white images of the objects, is available at

Most recently, the NEAT team has discovered two new Earth- crossing asteroids. One, designated 1998 HT31, is a relatively small Apollo-type asteroid 270 meters (800 feet) in diameter; the other, 1998HD14, is the 30th Aten to be discovered since JPL astronomer Eleanor Helin first identified this class of asteroid 22 years ago, and the fifth discovered with the NEAT tracking system. Both are classified as potentially hazardous asteroids because their orbits come within 5 million kilometers (3 million miles) of Earth, or about 20 times the distance of the Moon. However, neither currently poses a threat to Earth.

"Atens are a rare class of asteroid because of their small orbits, which are smaller than that of Earth's, and which never allow them to wander far from our planet," said Helin, who is the principal investigator of the NEAT program. "1998 HD14 passed within 5 million kilometers (3 million miles of Earth) just a week after we discovered it on April 29. This is relatively close but poses no threat in the foreseeable future. Atens are of particular interest to us because they stay so close to Earth's orbit."

Along with near-Earth asteroids, astronomers are also interested in tracking long-period comets, which travel vast distances from the Oort Cloud, a region far beyond Pluto's orbit, which is believed to house trillions of incipient comets. These objects travel in very long paths through the solar system, and can appear unannounced, with no calling cards.

"We are particularly interested in these comets because they give us little time before appearing in Earth's vicinity," Helin said.

Astronomers dedicated to discovering and tracking near-Earth objects are eager to find all of the potentially dangerous asteroids and comets long before they are likely to approach Earth. For instance, the NEAT team at JPL is developing two new CCD cameras and hopes to install them at Mt. Haleakala or other facilities.

"With additional telescopes, longer observational runs and our new operating system, we will be able to detect 90 percent of the Earth-crossing asteroids that are larger than 1 kilometer (6/10ths of a mile) in diameter in the next 10 years," Pravdo said. "As our knowledge about these objects grows, we will be able to provide better information which can be used in studies of ways to divert Earth-crossers on threatening orbits toward Earth."

NEAT was built and is being managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology in Pasadena, CA.

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