Scientists working with NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif., have released a new and improved movie clip of near-Earth asteroid 1998 QE2 and its moon. The 55 individual images used in the movie were generated from data collected at Goldstone on June 1, 2013.
The asteroid’s satellite, or moon, is approximately 2,000 feet (600 meters) wide, has an elongated appearance, and completes a revolution around its host body about once every 32 hours. At any point during its orbit, the maximum distance between the primary body and moon is about 4 miles (6.4 kilometers). Similar to our moon, which always points the same “face” at Earth, the asteroid’s satellite appears to always show the same portion of its surface to the primary asteroid. This is called “synchronous rotation.”
The radar data indicate the main, or primary body, is approximately 1.9 miles (3 kilometers) in diameter and has a rotation period of about five hours. This makes 1998 QE2 one of the slowest (with respect to its rotation) and largest binaries that have been observed by planetary radar. In the near-Earth population, about 16 percent of asteroids that are about 655 feet (200 meters) or larger are binary or triple systems.
Each of the individual images obtained on June 1, 2013, required about five minutes of data collection by the Goldstone radar. At the time of the observations that day, asteroid 1998 QE2 was about 3.75 million miles (6 million kilometers) from Earth. The resolution is about 125 feet (38 meters) per pixel.
The trajectory of asteroid 1998 QE2 is well understood. The closest approach of the asteroid occurred on May 31 at 1:59 p.m. PDT (4:59 p.m. EDT / 20:59 UTC), when the asteroid got no closer than about 3.6 million miles (5.8 million kilometers), or about 15 times the distance between Earth and the moon. This was the closest approach the asteroid will make to Earth for at least the next two centuries.