Unexpected Surprises Revealed: NASA’s Planetary Radar Images Asteroid As It Approaches Earth

During the close approach of 2008 OS7 with Earth on February 2, the agency’s Deep Space Network planetary radar gathered the first detailed images of the stadium-size asteroid.

On February 2, a large asteroid safely drifted past Earth at a distance of about 1.8 million miles (2.9 million kilometers, or 7 ½ times the distance between Earth and the Moon). There was no risk of the asteroid – called 2008 OS7 – impacting our planet, but scientists at NASA’s Jet Propulsion Laboratory in Southern California used a powerful radio antenna to better determine the size, rotation, shape, and surface details of this near-Earth object (NEO). Until this close approach, asteroid 2008 OS7 had been too far from Earth for planetary radar systems to image it.

Discovery and Observations
The asteroid was discovered on July 30, 2008, during routine search operations for NEOs by the NASA-funded Catalina Sky Survey, which is headquartered at the University of Arizona in Tucson. After discovery, observations of the amount of light reflected from the asteroid’s surface revealed that it was roughly between 650 to 1,640 feet (200 and 500 meters) wide and that it is comparatively slow rotating, completing one rotation every 29 ½ hours.