"With these first radar observations finished, we can guarantee that next week's 1.4-lunar-distance approach is the closest until at least the end of the next century," said Steve Ostro, JPL astronomer and principal investigator for the project. "It is also the asteroid's closest Earth approach for more than 2,000 years."

Scientists at NASA's Near-Earth Object Program Office at JPL have determined that there is no possibility of an impact with Earth in the foreseeable future.

Asteroid 2007 TU24 was discovered by the NASA-sponsored Catalina Sky Survey on Oct. 11, 2007. The first radar detection of the asteroid was acquired on Jan. 23 using the Goldstone 70-meter (230-foot) antenna. The Goldstone antenna is part of NASA's Deep Space Network Goldstone station in Southern California's Mojave Desert. Goldstone's 70-meter diameter (230-foot) antenna is capable of tracking a spacecraft traveling more than 16 billion kilometers (10 billion miles) from Earth. The surface of the 70-meter reflector must remain accurate within a fraction of the signal wavelength, meaning that the precision across the 3,850-square-meter (41,400-square-foot) surface is maintained within one centimeter (0.4 inch).

Ostro and his team plan further radar observations of asteroid 2007 TU24 using the National Science Foundation's Arecibo Observatory in Puerto Rico on Jan. 27-28 and Feb. 1-4.

The asteroid will reach an approximate apparent magnitude 10.3 on Jan. 29-30 before quickly becoming fainter as it moves farther from Earth. On that night, the asteroid will be observable in dark and clear skies through amateur telescopes with apertures of at least 7.6 centimeters (three inches). An object with a magnitude of 10.3 is about 50 times fainter than an object just visible to the naked eye in a clear, dark sky.

Scientists working with Ostro on the project include Lance Benner and Jon Giorgini of JPL, Mike Nolan of the Arecibo Observatory, and Greg Black of the University of Virginia.

http://www.eurekalert.org/pub_releases/2008-01/cuc-aap012508.php earlier related report
Arecibo Astronomers Prepare To Obtain Close Images Of A Near-Earth Asteroid
Ithaca NY - The Arecibo Observatory in Arecibo, Puerto Rico will observe a newly discovered asteroid on Jan. 27-28, as the object called 2007 TU24 passes within 1.4 lunar distances, or 334,000 miles, from Earth.

The asteroid, estimated at between 150 and 600 meters in diameter - about 500 feet to 1,900 feet, or the size of a football field, at 360 feet, to the size of Chicago's 110-story Sears Tower, at 1,454 feet - was discovered by the University of Arizona's Catalina Sky Survey in October 2007.

It poses no threat to Earth, but its near approach gives Arecibo astronomers a golden opportunity to learn more about potentially hazardous near-Earth objects.

"We don't yet know anything about this asteroid," said Mike Nolan, head of radar astronomy at the Puerto Rico observatory. Such objects pass near Earth with relative frequency, he said - approximately one every five years or so - but it's rare that astronomers have enough advance notice to plan for rigorous observing.

"Because it's coming so close, we'll get our highest quality imaging," said Nolan.

Using Arecibo's powerful radar, which is the most sensitive in the world, researchers will gauge the object's size, observe its speed and measure its spin.

Switching then to imaging mode, which will offer resolution to 7.5 meters - three times more precise than NASA's Goldstone telescope, the only other radar telescope in the world - the researchers hope to map the object's surface in detail. The Robert C. Byrd Green Bank Telescope, Green Bank, W.Va., will receive Arecibo's echo from the asteroid and transmit its data back to Arecibo.

TU24 is one of an estimated 7,000 near-Earth objects, its size or larger

- most have never been closely studied.

"We have good images of a couple dozen objects like this, and for about one in 10, we see something we've never seen before," said Nolan. "We really haven't sampled the population enough to know what's out there."

Arecibo's radar is vital for continuing to classify and understand such objects, said Cornell University assistant professor of astronomy Jean-Luc Margot. "Arecibo does a fantastic job at getting images, discovering the shape, spin and reflection properties of such an object . . . All these things that are important to know.'

The telescope will be trained on TU24 Jan. 27-28 and again Feb. 1-4. Goldstone's planetary radar observed it Jan. 23-24.

Steven Ostro, astronomer at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., is principal investigator for the project; also contributing are Lance Benner and Jon Giorgini at JPL and Greg Black of the University of Virginia. Their research is funded by NASA. NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," discovers, characterizes and computes trajectories for these objects to determine if any could be potentially hazardous to our planet. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, a national research center operated by Cornell University, Ithaca, N.Y., for the National Science Foundation. JPL is a division of the California Institute of Technology in Pasadena.

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