CANADA: NASA scientists have used two giant, Earth-based radio telescopes to bounce radar signals off a passing asteroid and produce images of the peanut-shaped body as it approached close to Earth this past weekend.
The asteroid appears to be a contact binary—an asteroid with two lobes that are stuck together.
The images show the rotation of the asteroid, named 1999 JD6, which made its closest approach on July 24 at 9:55 p.m. PDT (12:55 a.m. EDT on July 25) at a distance of about 4.5 million miles (7.2 million kilometers, or about 19 times the distance from Earth to the moon).
“Radar imaging has shown that about 15 percent of near-Earth asteroids larger than 600 feet [about 180 meters], including 1999 JD6, have this sort of lobed, peanut shape,” said Lance Benner of NASA’s Jet Propulsion Laboratory in Pasadena, California, who leads NASA’s asteroid radar research program.
To obtain the views, researchers paired NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, California, with the 330-foot (100-meter) National Science Foundation Green Bank Telescope in West Virginia. Using this approach, the Goldstone antenna beams a radar signal at an asteroid and Green Bank receives the reflections. The technique, referred to as a bistatic observation, dramatically improves the amount of detail that can be seen in radar images. The new views obtained with the technique show features as small as about 25 feet (7.5 meters) wide.
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