NASA’s planetary radar tracks two close approaches of large asteroids

The Deep Space Network’s Goldstone Planetary Radar had a busy few days observing asteroids 2024 MK and 2011 UL21 as they safely passed Earth.

Scientists at NASA’s Jet Propulsion Laboratory in Southern California recently tracked two asteroids that flew by our planet. One was shown to have a small moon orbiting it, while the other was discovered just 13 days before its closest approach to Earth. There was no risk of any of the close objects impacting our planet, but the radar observations made during these two close approaches will provide valuable practice for planetary defense, as well as information on their sizes, orbits, rotation, surface details and clues. on their composition and creation.

Asteroid 2011 UL21, which passed Earth on June 27 at a distance of 4.1 million miles (6.6 million kilometers), about 17 times the distance between the Moon and Earth, was discovered in 2011 by the Catalina Sky Survey in Tucson, Arizona. But this is the first time it has come close enough to Earth to be picked up by radar. While the nearly mile-wide (1.5 kilometer wide) object is classified as potentially hazardous, calculations of its future orbits show that it will not pose a threat to our planet anytime soon.

Using the 230-foot-wide (70-meter) Goldstone Solar System Radar, called Deep Space Station 14 (DSS-14), near Barstow, California, JPL scientists sent radio waves to the asteroid and received the reflected signals. same antenna. In addition to determining that the asteroid is roughly spherical, they discovered that it is a binary system: A smaller asteroid, or moon, orbits it from a distance of about 3 km.

“About two-thirds of asteroids of this size are thought to be binary systems, and their discovery is particularly important because we can use measurements of their relative positions to estimate their relative orbits, masses and densities, providing key information about how they may have formed, said Lance Benner, JPL principal scientist who helped lead the observations.

The second close approach

Two days later, on June 29, the same team observed asteroid 2024 MK pass our planet from a distance of just 184,000 miles (295,000 kilometers), a little more than three-quarters of the distance between the Moon and Earth. About 500 feet (150 meters) wide, this asteroid appears elongated and angular, with prominent flat and rounded areas.

For these observations, the scientists also used DSS-14 to transmit radio waves to the object, but used Goldstone’s 114-foot (34-meter) DSS-13 antenna to receive the signal that bounced off the asteroid and returned to Earth. The result of this “bistatic” radar observation is a detailed image of the asteroid’s surface, revealing concavities, ridges and boulders about 30 feet (10 meters) wide.

Close approaches to near-Earth objects the size of 2024 MK are relatively rare, occurring on average every few decades, so the JPL team tried to gather as much data as possible about the object.

“This was an extraordinary opportunity to explore the physical properties and obtain detailed images of a near-Earth asteroid,” Benner said.

Asteroid 2024 MK was first reported on June 16 by the Asteroid Impact Last Alert System (ATLAS) at the Sutherland Observatory in South Africa. Its orbit was altered by Earth’s gravity as it passed by, shortening its 3.3-year orbital period around the Sun by about 24 days. Although it is classified as a potentially dangerous asteroid, calculations of its future motion show that it does not pose a threat to our planet in the foreseeable future.