Posted Tuesday, November 8, 2011 --- 6:00 a.m.

LOS ANGELES (AP) -- Scientists have been tracking an asteroid the size of an aircraft carrier that's set to make a close but harmless swing by Earth.

At closest approach, the quarter-mile-wide space rock will pass within 202,000 miles of our planet at 6:28 p.m. Eastern time Tuesday.

Experts at NASA's Near-Earth Object Program, which monitors asteroids and comets, say there's zero chance of an impact. They're using the close encounter to learn more about the asteroid known as 2005 YU55.

Since late last week, antennas at NASA's Deep Space Network in California have been tracking the spinning asteroid. The last time one this big zipped by Earth was in 1976.

Amateur skygazers with a 6-inch telescope or larger may glimpse the asteroid if skies are clear and they know where to look.

Copyright 2011. The Associated Press.