A NASA astronomer said yesterday that he tried and failed Dec. 20 to use the world's largest radio telescope to get a radar image of a puzzling, asteroidlike object that passed within 288,000 miles of Earth.
Astronomers had hoped the observation would settle the question of whether the object -- which is circling the sun in an orbit slightly larger than that of the Earth -- is a highly unusual asteroid or a piece of booster rocket somehow tossed out of Earth orbit.
Instead, the tiny object, which may be less than 20 feet long, remains a mystery. It comes close to the Earth only once every 16 years.
Steven Ostro of the National Aeronautics and Space Administration's Jet Propulsion Laboratory in Pasadena, Calif., said that when he aimed the 1,000-foot radio dish in Arecibo, Puerto Rico, at the likely position of the object, "we did not see the echoes."