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Barely two weeks after the failure of a doomsday prediction by a United States (U.S.) based preacher, Russia and U.S. scientists are at war over another perceived threat to human existence.

The danger this time is not an apocalyptic occurrence, but the smacking of the Earth by a giant asteroid in five months time.

The potentially perilous space rock is known as Asteroid 2005 YU55, a round mini-world that is about 1,300 feet (400 metres) in diametre.

According to U.S. scientists, this asteroid will approach the Earth within a scant 0.85 lunar distances in early November.

Due to its size, and the way it will whisk by so close to the Earth, an extensive campaign of radar, visual and infrared observations are being planned.

U.S. scientists say there is no cause for alarm, but the Russians have issued a report saying there's something to fear.

NASA rejects the Russian report, calling the chances of the asteroid hitting the Earth 'minuscule'.

Asteroid 2005 YU55 was discovered by Spacewatch at the University of Arizona, Tucson's Lunar and Planetary Laboratory on December 28, 2005.

According to Spacewatch, the asteroid is "en route and headed our way, the cosmic Wanderer is another reminder about life here on our sitting duck of a planet'.

"The close Earth approach of 2005 YU55, on November 8, is unusual since it is close and big. On average, one wouldn't expect an object this big to pass this close but every 30 years," said Don Yeomans, manager of NASA's Near-Earth Object Programme Office and the Jet Propulsion Laboratory in Pasadena, California.

Yeomans said that with new radar capabilities at Goldstone in California - part of NASA's Deep Space Network - there is a good chance of obtaining radar imaging of 2005 YU55 down to the five-meter resolution level. Doing so, he said, would mean obtaining higher spatial resolution of the object than that attained by recent spacecraft flyby missions.

"So, we like to think of this opportunity as a close flyby mission with Earth as the spacecraft," Yeomans told SPACE.com. "When combined with ground-based optical and near-infrared observations, the radar data should provide a fairly complete picture of one of the larger potentially hazardous asteroids," he said.

Asteroid 2005 YU55 is a slow rotator. Because of its size and proximity to Earth, the Minor Planet Centre in Cambridge, Massachusetts, has designated the space rock as a "potentially hazardous asteroid".

"We're already preparing for the 2005 YU55 flyby," said Lance Benner, a research scientist at JPL and a specialist on radar imaging of near-Earth objects. He said part of the plan was to observe the asteroid with radar, using both the huge Arecibo dish in Puerto Rico and equipment at Goldstone.

"The asteroid will approach from the south, so Goldstone has the first chance to observe it due to its declination coverage," Benner said.

To help coordinate the observing campaigns, "Radar Observations Planning" websites have been set up for the unusual occasion, Benner said.

"This flyby will be the closest by any near-Earth asteroid with an absolute magnitude this bright since 1976 and until 2028," Benner added. "Nobody saw 2010 XC15 during its close flyby, within 0.5 lunar distances, in 1976."

He noted that the asteroid wasn't discovered until late in 2010.

"Thus, the flyby by 2005 YU55 will be the closest actually observed by something this large, so it represents a unique opportunity," Benner said. "In a real sense, this will provide imaging resolution comparable to or even better than a spacecraft mission flyby."

Benner said that because the asteroid would be zooming by Earth so very close, radar echoes would be extremely strong.

Benner explained that initially, the object will be too close to the Sun and too faint for optical observers. But late in the day on November 8, the solar elongation will grow sufficiently to see it. Early on November 9, the asteroid could reach about 11th magnitude for several hours before it fades as its distance rapidly increases, Benner explained.

Even if the Earth escapes the looming danger, Russian scientists say that there is a bigger threat called Apophis in the future.

In 2004, NASA scientists announced that there was a chance that Apophis, an asteroid larger than two football fields, could smash into Earth in 2029. A few additional observations and some number-crunching later, astronomers noted that the chance of the planet-killer hitting Earth in 2029 was nearly zilch.

But reports out of Russia say that scientists there estimate Apophis will collide with Earth on April 13, 2036. These reports conflict on the probability of such a doomsday event.

"Technically, they're correct, there is a chance in 2036 (that Apophis will hit Earth)," said Donald Yeomans, head of NASA's Near-Earth Object Programme Office. However, that chance is just 1-in-250,000, Yeomans said.

The Russian scientists are basing their predictions of a collision on the chance that the 900-foot-long (270 meters) Apophis will travel through what's called a gravitational keyhole as it passes by Earth in 2029.

The gravitational keyhole they mention is a precise region in space, only slightly larger than the asteroid itself, in which the effect of Earth's gravity is such that it could tweak Apophis' path.

"The situation is that in 2029, April 13, (Apophis) flies very close to the Earth, within five Earth radii, so that will be quite an event, but we've already ruled out the possibility of it hitting at that time," Yeomans told Life's Little Mysteries. "On the other hand, if it goes through what we call a keyhole during that close Earth approach ... then it will indeed be perturbed just right so that it will come back and smack Earth on April 13, 2036," Yeomans said.

The chances of the asteroid going through the keyhole, which is tiny compared to the asteroid, are "minuscule," Yeomans added.

This is the scientists' description of the more likely scenario: Apophis will make a fairly close approach to Earth in late 2012 and early 2013, and will be extensively observed with ground-based optical telescopes and radar systems. If it seems to be heading on a destructive path, NASA will devise the scheme and machinery necessary to change the asteroid's orbit, decreasing the probability of a collision in 2036 to zero, Yeomans said.

There are several ways to change an asteroid's orbit, the simplest of which is to run a spacecraft into the hurtling rock. This technology was used on July 4, 2005, when Deep Impact smashed into the comet Tempel 1.

Meanwhile, October 21, 2011, has been set as another end of the world date by Harold Camping, the 89-year-old retired civil engineer who has built a multi-million-dollar Christian media-empire that publicises his apocalyptic prediction. His last doomsday prediction failed on May 21.

Camping has preached that some 200 million people would be saved, and that those left behind would die in a series of scourges visiting Earth until the globe is consumed by a fireball on October 21.