The highest-resolution radar images of asteroid 2015 TB145‘s safe flyby of Earth have been processed. NASA scientists used giant, Earth-based radio telescopes to bounce radar signals off the asteroid as it flew past Earth on 31 October at 17:00 UTC (~5pm GMT) at about 1.3 lunar distances (302,500 miles, or 486,800 kilometres) from Earth. Asteroid 2015 TB145 is spherical in shape and approximately 2,000 feet (600 metres) in diameter.
“The radar images of asteroid 2015 TB145 show portions of the surface not seen previously and reveal pronounced concavities, bright spots that might be boulders, and other complex features that could be ridges,” said Lance Benner of NASA’s Jet Propulsion Laboratory in Pasadena, California, who leads NASA’s asteroid radar research program. “The images look distinctly different from the Arecibo radar images obtained on 30 October and are probably the result of seeing the asteroid from a different perspective in its three-hour rotation period.”
To obtain these highest-resolution radar images of the asteroid, scientists used the 230-foot (70-metre) DSS-14 antenna at Goldstone, California, to transmit high-power microwaves toward the asteroid. The signal bounced off the asteroid, and its radar echoes were received by the National Radio Astronomy Observatory’s 100-metre (330-foot) Green Bank Telescope in West Virginia. The radar images achieve a spatial resolution as fine as 13 feet (4 metres) per pixel.
“Working with our observatory partners, we were able to get our resolution down to less than 13 feet (four metres) per pixel,” said Shantanu Naidu, a postdoctoral student at the California Institute of Technology in Pasadena, and a member of the radar team. “It is a truly remarkable achievement — one which we will later be able to apply when future flyby opportunities present themselves.”
The next time that asteroid 2015 TB145 will be in Earth’s neighbourhood will be in September 2018, when it will make a distant pass at about 24 million miles (38 million kilometres), or about a quarter the distance between Earth and the Sun.
Radar is a powerful technique for studying an asteroid’s size, shape, rotation, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than would be possible otherwise.