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 by Staff Writers Washington DC (SPX) Sep 27, 2022
After 10 months flying in space, NASA's Double Asteroid Redirection Test (DART) - the world's first planetary defense technology demonstration - successfully impacted its asteroid target on Monday, the agency's first attempt to move an asteroid in space. Mission control at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, announced the successful impact at 7:14 p.m. EDT. As a part of NASA's overall planetary defense strategy, DART's impact with the asteroid Dimorphos demonstrates a viable mitigation technique for protecting the planet from an Earth-bound asteroid or comet, if one were discovered. "At its core, DART represents an unprecedented success for planetary defense, but it is also a mission of unity with a real benefit for all humanity," said NASA Administrator Bill Nelson. "As NASA studies the cosmos and our home planet, we're also working to protect that home, and this international collaboration turned science fiction into science fact, demonstrating one way to protect Earth." DART targeted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos. Neither asteroid poses a threat to Earth.
The mission's one-way trip confirmed NASA can successfully navigate a spacecraft to intentionally collide with an asteroid to deflect it, a technique known as kinetic impact. The investigation team will now observe Dimorphos using ground-based telescopes to confirm that DART's impact altered the asteroid's orbit around Didymos. Researchers expect the impact to shorten Dimorphos' orbit by about 1%, or roughly 10 minutes; precisely measuring how much the asteroid was deflected is one of the primary purposes of the full-scale test. "Planetary Defense is a globally unifying effort that affects everyone living on Earth," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "Now we know we can aim a spacecraft with the precision needed to impact even a small body in space. Just a small change in its speed is all we need to make a significant difference in the path an asteroid travels." The spacecraft's sole instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), together with a sophisticated guidance, navigation and control system that works in tandem with Small-body Maneuvering Autonomous Real Time Navigation (SMART Nav) algorithms, enabled DART to identify and distinguish between the two asteroids, targeting the smaller body. These systems guided the 1,260-pound (570-kilogram) box-shaped spacecraft through the final 56,000 miles (90,000 kilometers) of space into Dimorphos, intentionally crashing into it at roughly 14,000 miles (22,530 kilometers) per hour to slightly slow the asteroid's orbital speed. DRACO's final images, obtained by the spacecraft seconds before impact, revealed the surface of Dimorphos in close-up detail. Fifteen days before impact, DART's CubeSat companion Light Italian CubeSat for Imaging of Asteroids (LICIACube), provided by the Italian Space Agency, deployed from the spacecraft to capture images of DART's impact and of the asteroid's resulting cloud of ejected matter. In tandem with the images returned by DRACO, LICIACube's images are intended to provide a view of the collision's effects to help researchers better characterize the effectiveness of kinetic impact in deflecting an asteroid. Because LICIACube doesn't carry a large antenna, images will be downlinked to Earth one by one in the coming weeks. "DART's success provides a significant addition to the essential toolbox we must have to protect Earth from a devastating impact by an asteroid," said Lindley Johnson, NASA's Planetary Defense Officer. "This demonstrates we are no longer powerless to prevent this type of natural disaster. Coupled with enhanced capabilities to accelerate finding the remaining hazardous asteroid population by our next Planetary Defense mission, the Near-Earth Object (NEO) Surveyor, a DART successor could provide what we need to save the day." With the asteroid pair within 7 million miles (11 million kilometers) of Earth, a global team is using dozens of telescopes stationed around the world and in space to observe the asteroid system. Over the coming weeks, they will characterize the ejecta produced and precisely measure Dimorphos' orbital change to determine how effectively DART deflected the asteroid. The results will help validate and improve scientific computer models critical to predicting the effectiveness of this technique as a reliable method for asteroid deflection. "This first-of-its-kind mission required incredible preparation and precision, and the team exceeded expectations on all counts," said APL Director Ralph Semmel. "Beyond the truly exciting success of the technology demonstration, capabilities based on DART could one day be used to change the course of an asteroid to protect our planet and preserve life on Earth as we know it." Roughly four years from now, the European Space Agency's Hera project will conduct detailed surveys of both Dimorphos and Didymos, with a particular focus on the crater left by DART's collision and a precise measurement of Dimorphos' mass. DART's Final Images Prior to Impact
Direct impact or nuclear weapons? How to save Earth from an asteroid The operation is like playing billiards in space, using Newton's laws of motion to guide us. If an asteroid threat to Earth were real, a mission might need to be launched a year or two in advance to take on a small asteroid, or decades ahead of projected impact for larger objects hundreds of kilometers in diameter that could prove catastrophic to the planet. Or, a larger object might require hits with multiple spacecraft. "This demonstration will start to add tools to our toolbox of methods that could be used in the future," said Lindley Johnson, NASA's planetary defense office, in a recent briefing. Other proposed ideas have included a futuristic-sounding "gravity tractor," or a mission to blow up the hypothetical object with a nuclear weapon -- the method preferred by Hollywood. - Gravity tractor - Should an approaching object be detected early -- years or decades before it would hit Earth -- a spaceship could be sent to fly alongside it for long enough to divert its path via using the ship's gravitational pull, creating a so-called gravity tractor. This method "has the virtue that the method of moving the asteroid is totally well understood -- it's gravity and we know how gravity works," Tom Statler, a DART program scientist at NASA said at a briefing last November when DART launched. The mass of the spacecraft however would be a limiting factor -- and gravity tractors would be less effective for asteroids more than 500 meters in diameter, which are the very ones that pose the greatest threat. In a 2017 paper, NASA engineers proposed a way to overcome this snag: by having the spacecraft scoop material from the asteroid to enhance its own mass, and thus, gravity. But none of these concepts have been tried, and would need decades to build, launch and test. - Nuclear detonation - Another option: launching nuclear explosives to redirect or destroy an asteroid. "This may be the only strategy that would be effective for the largest and most dangerous 'planet-killer' asteroids (more than one kilometer in diameter)," a NASA article on the subject says, adding such a strike might be useful as a "last resort" in case the other methods fail. But these weapons are geopolitically controversial and technically banned from use in outer space. Lori Glaze, NASA's planetary science division director said in a 2021 briefing that the agency believed the best way to deploy the weapons would be at a distance from an asteroid, in order to impart force on the object without blowing it into smaller pieces that could then multiply the threat to Earth. A 2018 paper published in the "Journal of Experimental and Theoretical Physics" by Russian scientists looked at the direct detonation scenario. E. Yu. Aristova and colleagues built miniature asteroid models and blasted them with lasers. Their experiments showed that blowing up a 200-meter asteroid would require a bomb 200 times as powerful as the one that exploded over Hiroshima in 1945. They also said it would be most effective to drill into the asteroid, bury the bomb, then blow it up -- just like in the movie Armageddon.
Direct impact or nuclear weapons? How to save Earth from an asteroid The operation is like playing billiards in space, using Newton's laws of motion to guide us. If an asteroid threat to Earth were real, a mission might need to be launched a year or two in advance to take on a small asteroid, or decades ahead of projected impact for larger objects hundreds of kilometers in diameter that could prove catastrophic to the planet. Or, a larger object might require hits with multiple spacecraft. "This demonstration will start to add tools to our toolbox of methods that could be used in the future," said Lindley Johnson, NASA's planetary defense office, in a recent briefing. Other proposed ideas have included a futuristic-sounding "gravity tractor," or a mission to blow up the hypothetical object with a nuclear weapon -- the method preferred by Hollywood. - Gravity tractor - Should an approaching object be detected early -- years or decades before it would hit Earth -- a spaceship could be sent to fly alongside it for long enough to divert its path via using the ship's gravitational pull, creating a so-called gravity tractor. This method "has the virtue that the method of moving the asteroid is totally well understood -- it's gravity and we know how gravity works," Tom Statler, a DART program scientist at NASA said at a briefing last November when DART launched. The mass of the spacecraft however would be a limiting factor -- and gravity tractors would be less effective for asteroids more than 500 meters in diameter, which are the very ones that pose the greatest threat. In a 2017 paper, NASA engineers proposed a way to overcome this snag: by having the spacecraft scoop material from the asteroid to enhance its own mass, and thus, gravity. But none of these concepts have been tried, and would need decades to build, launch and test. - Nuclear detonation - Another option: launching nuclear explosives to redirect or destroy an asteroid. "This may be the only strategy that would be effective for the largest and most dangerous 'planet-killer' asteroids (more than one kilometer in diameter)," a NASA article on the subject says, adding such a strike might be useful as a "last resort" in case the other methods fail. But these weapons are geopolitically controversial and technically banned from use in outer space. Lori Glaze, NASA's planetary science division director said in a 2021 briefing that the agency believed the best way to deploy the weapons would be at a distance from an asteroid, in order to impart force on the object without blowing it into smaller pieces that could then multiply the threat to Earth. A 2018 paper published in the "Journal of Experimental and Theoretical Physics" by Russian scientists looked at the direct detonation scenario. E. Yu. Aristova and colleagues built miniature asteroid models and blasted them with lasers. Their experiments showed that blowing up a 200-meter asteroid would require a bomb 200 times as powerful as the one that exploded over Hiroshima in 1945. They also said it would be most effective to drill into the asteroid, bury the bomb, then blow it up -- just like in the movie Armageddon.
Mission seeks to test technology to mitigate potential asteroid or comet impacts of Earth Tucson AZ (SPX) Sep 27, 2022 NASA's Double Asteroid Redirection Test (DART) spacecraft successfully hit its target Sept. 26, and now scientists are analyzing to what degree the kinetic impact changed the trajectory of Dimorphos, the asteroid moonlet of Didymos. The mission is a test to see if hitting a body headed for Earth with a small spacecraft could redirect the threat away from us. Five Planetary Science Institute scientists, Jian-Yang Li, Eric Palmer, Steven Schwartz, Amanda Sickafoose and Jordan Steckloff are wor ... read more
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