NASA’s Goldstone Planetary Radar System recently recorded two near-Earth asteroids, 2024 MK and 2011 UL21, passing by our planet. Perhaps a little alarmingly, one was only discovered for 13 days before being safely bypassed The Earthbut NASA scientists Jet Engine Laboratory (JPL) in Southern California say it never posed a threat. Still, the images they were able to gather were extremely informative.
“There was no risk of a near-Earth object impacting our planet, but the radar observations made during these two close approaches will provide valuable practice for planetary protectionas well as information about their sizes, orbits, rotation, surface details, and clues to their composition and formation,” the team wrote in a press release.
The Goldstone Solar System Radar is located in the desert near Barstow, California. With its 70-meter (230 ft) fully steerable antenna (DSS-14)—the world’s only fully steerable range and high-resolution imaging radar—it provides all-sky coverage and has been used to survey objects of interest within on solar system for the last three decades.
During this time he was able to collect invaluable information about other planets, from mercury to Saturnand has supported numerous exploration missions, such as the Mars Exploration Rovers, the Cassini Expedition to Saturn, the Hayabusa Asteroid Explorers, SOHO the recovery of the sun observation probe, Lunar Prospector and Venus– study of the Magellan venture.
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As seen this week, it has also been used to track and study proximity to Earth asteroids, helping to prevent potential impact hazards and identify targets for future exploration missions. Radar is a powerful tool for studying the properties and orbits of asteroids—the ground station transmits radio waves to asteroids, then receives back-scattered signals that scientists can use to gather relevant information. If the “echo” of an object is strong enough, the radar image can achieve spatial resolution to identify features up to 10 meters (32 meters) in size.
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On June 27, the radar system tracked asteroid 2011 UL21 as it passed Earth at a distance of 4.1 million miles (6.6 million kilometers). As its name suggests, the asteroid is known for NASA 2011 scientists discovered during the Catalina Sky Survey in Tucson, Arizona.
About a mile wide (1.6 kilometers wide), this object was the first to come close enough to be imaged by Earth-based radar, allowing scientists to determine that it is roughly spherical in shape and that it is accompanied by its own “moon” that orbits at a distance of about 1.9 miles (3 kilometers) from the asteroid.
“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, which provide key information about how they might have formed,” said Lance Benner, JPL principal scientist who helped conduct the observations.
While NASA scientists say that due to its size, 2011 UL21 is classified as potentially hazardous, calculations of the asteroid’s orbit indicate that it will not pose a real threat in the near future.
Then, just two days later, another asteroid appeared. The same team watched asteroid 2024 MK pass our planet at a distance of just 184,000 miles (295,000 kilometers), just over three-quarters of the distance between The moon and the Earth. Close approaches like this are relatively rare, according to the team, but provide valuable insights that would otherwise be difficult to obtain.
“This was an outstanding opportunity to study the physical properties and obtain detailed images of a near-Earth asteroid,” Benner said.
2024 MK was first identified on June 16 by the Impact Asteroid Last Alert System (ATLAS) at the Sutherland Observatory in South Africa. “Its orbit was modified by Earth’s gravity as it passed by, reducing its 3.3-year orbital period by the sun by about 24 days,” the team said in the release.
On June 29, scientists again transmitted radio waves to 2024 MK – but this time, received the return signal with Goldstone’s 114-foot (34-meter) DSS-13 antenna rather than the DSS-14. “This ‘bistatic’ radar observation produced a detailed image of the asteroid’s surface, revealing depressions, ridges and boulders about 30 feet (10 meters) wide,” they wrote.
About 500 feet (150 meters) wide, this asteroid appears elongated and angular, with prominent flat and rounded areas. Although it is also 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.
