Arecibo Radar Images of 2007 TU24

Asteroid Image


This radar image of 2007 TU24 was obtained on January 28, 2008, about
12 hours before the asteroid's 1.4-lunar-distance pass by the Earth,
from an observation that used the Arecibo telescope to transmit a
300-kilowatt beam of radio energy toward the asteroid and the Robert C.
Byrd Green Bank Telescope, (GBT) in West Virginia to receive the echoes.

The image summed echoes recorded over about three minutes.

The intrinsic resolution of the image is about eight meters (25 feet).
Distance from the Earth increases from top to bottom.
Unlike normal optical images, radar images show how echo power is
distributed in range, or distance from the viewer, and Doppler
frequency, which is proportional to how fast a resolution cell is
moving toward or away from the viewer:
In this image, speed toward the Earth increases from left to right.

Despite the unusual radar imaging geometry, the image reveals
important characteristics of this object.  Its visible extent is
about 100 meters, and since typically about half of an object is
concealed from our view, the object's overall extent probably is
around 200 meters.  The object also is clearly at least slightly
asymmetrical, and also show evidence for nonuniform, probably
nonconvex topography.  Images with similar resolution obtained on
Jan. 28 and during observations planned for Feb. 1-4 should show other
orientations of the object, and may permit estimation of its
three-dimensional shape.

This experiment produced 8-meter-resolution images of a 0.2-km asteroid
when it was about 540,000 km away.
This is like using a camera in New York to image a person in Los
Angeles with several-inch resolution.