"An asteroid discovered in 2004 will have its closest encounter with Earth today," said Andrei Finkelstein, head of St. Petersburg's Institute of Applied Astronomy, home to the nation's main observatory.
The asteroid, known as 2004 XP14 and an estimated 800 meters wide, will pass about 433,000 kilometers (269,000 miles) from Earth, which is still too far to pose any threat either to the planet itself or to any of its orbital satellites, said Nikolai Ivanov, the chief ballistic expert at Russian Mission Control, outside Moscow.
He said telecommunications satellites were in orbits no farther than 36,000km (22,300 miles) from Earth and the International Space Station was only 350km (220 miles) away.
Finkelstein said that scientists around the world would be observing the 2004 XP14 as it flies by to determine its size and orbit.
"Two observatories - in Ukraine and America - will use their radars to send radiation beams to the asteroid. And many other observatories, including in the North Caucasus, will be receiving return signals," he said, adding that the experiments could provide clues as to future approaches of asteroids to Earth and their potential impacts.
The 2004 XP14 is one of about 700 known celestial bodies that pose a potential threat to Earth.
Astronomers have said no global disasters related to asteroid impacts are likely to happen in the next few decades, but that Earth might suffer from an impact some time in the future.
"In 10 to 20 years' time, we will know for certain whether any cataclysms arising from the impact of a large asteroid are looming," said Nikolai Zheleznov, a senior fellow at the Applied Astronomy Institute. "We guarantee that sooner or later, some asteroid will collide with Earth. This is a question of when rather than if, but we cannot say just yet whether it will happen in 10 or in 100 million years. An asteroid strike led to the extinction of the dinosaurs, but if we face the danger now, I hope we will be able to avert it, as many ways to ward off destructive asteroids have been developed in theory."