An asteroid the size of a cruise ship was projected to hit Japan in the next decade.
NASA and other space agencies gathered at a planetary defense conference in Tokyo to come up with a plan to destroy the asteroid. The island was dependent on a fleet of robotic spaceships that would launch in the next few years.
The world's space agencies banded together in 2020 to launch four ships towards a menacing space rock. The ships hit their targets. Japan's cities and neighborhoods were spared from destruction.
None of these events happened. It was a simulation, the kind of exercise officials conduct on a regular basis. The practice drills for protecting the planet have become more and more dependent on the ability to repel an object from deep space on its way to a deadly rendezvous with Earth. No one knows if the technique will work. Our species has never tried to destroy an asteroid.
That is about to change. On Wednesday at 1:21 a.m. The Double Asteroid Redirection Test mission was launched by NASA from a US Space Force base in California. Next year, a 1,200-pound, refrigerator-size spaceship will slam into an asteroid at 15,000 miles per hour. If the mission succeeds, it will show for the first time that we can punch a potentially hazardous asteroid away from Earth.
Lindley Johnson, NASA's chief of planetary defense, said that they are testing DART before they need it. When we are trying to save a population on the Earth's surface, we don't want to be flying an untested capability.
NASA, a civilian agency that focuses mainly on exploration, climate monitoring and hunting for signs of past life in our solar system, is not used to spending $324 million on a DART mission. NASA has not traditionally been responsible for leading efforts to protect the United States from any security threat.
Congress assigned the agency the imperative of protecting the planet from dangerous objects that are in the vicinity of the sun and occasionally cross paths with our world in 2005. Tracking tens of thousands of near-Earth asteroids large enough to cause catastrophic damage is included. Lawmakers assigned NASA the task of cataloging 90 percent of the space rocks, but it missed the goal.
Kelly Fast, who manages NASA's Near-Earth Object Observations Program, said that it was important to find them before you could get them. You want to find these things a long time in advance.
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The DART is being encased for launch at the SpaceX facility in California.
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The DART is ready for launch on Tuesday morning.
The Planetary Defense Coordination Office was set up by NASA in 2016 after a report urged the agency to better organize its asteroid tracking efforts. The office led by Mr. Johnson is tasked with warning the Defense Department and Federal Emergency Management Agency of any threatening asteroids, which is one of NASA's few responsibilities leading a national response to a major disaster threat.
The DART mission shows how the agency is taking on this responsibility. NASA has been studying space rocks for decades. It has landed on the surface of Mars, plucked samples from a large asteroid, and even crashed a craft into the moon to study it. New challenges for the agency's engineers and scientists are posed by striking an asteroid hard enough to change its position in space.
The DART space probe will visit Dimorphos in September or October of 2022. The two asteroids are in a circle around the sun every two years and travel along an egg-shaped path. Dimorphos is the smaller of the two, and it is the one that completes a revolution of the larger rock every 11 hours and 55 minutes.
Dimorphos are not a threat to Earth. When NASA's DART spacecraft makes contact, it will be the smallest body ever visited by a spaceship. That will be a challenge.
The DART mission team is the first to ever test a technique to move an asteroid using their own capabilities and systems. It is a big milestone for our species. The dinosaurs did not have a DART mission.
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The Arecibo radar images of Didymos and Dimorphos were taken in November of 2003
DART will need to hit a bull's-eye when the asteroid system reaches its closest point to Earth, some 6.8 million miles away. It is a complex orbital choreography involving a precise launch time off Earth and intermittent firings of a dozen tiny onboard thrusters that will refine DART's path to collide with Dimorphos.
Andy Rivkin is the DART investigation team lead and he said that the mission is really hard. DART will rely on a fully automated process that begins four hours before impact and uses an onboard navigation system called SMART Nav.
He said that there wasn't a way to joystick it in.
Tom Statler is a DART program scientist at NASA.
DART is fairly easy to understand. He said that there was only one instrument on board. The precision of the navigation is beyond what we have done before.
The Italian Space Agency built a small satellite called LICIACube, which DART will deploy ten days before impact. This companion will be watching DART from 34 miles away and measuring the amount of debris kicked up from the impact. The asteroid will be photographed by the DART camera before it hits the ground.
Scientists at NASA and the Applied Physics Laboratory will measure how much Dimorphos's flight around Didymos changes after the impact of DART. The asteroids are small dots of light. The scientists will measure the time between flickers of reflected light that indicate that Dimorphos has crossed in front of Didymos, then passed behind it half an hour later.
The mission was a success if the asteroid was sped up by at least 73 seconds. He thinks there will be a change to the asteroid's position.
He said the amount would be 10 minutes.
Astronomers don't know if the impact will leave a large crater or cause a cloud of debris.
There is a video
The Didymos system is around the Sun.
The composition of Dimorphos is not known. Little debris will be kicked up if the space rock is hard and dense. If Dimorphos turns out to be soft, like a tightly packed cluster of smaller space rocks, then DART's impact will leave a large crater and create a plume of debris that mission managers hope will help push the asteroid farther off its path with Didymos. The debris will give scientists an early idea of the direction the asteroid is likely to go.
How that ejected crater material behaves is a wild card. The first data point on that behavior will be provided by DART.
NASA will get a confirmed weapon in its planetary-defense arsenal if the test is successful. Astronomers say that other conceptual deflection methods might be better for asteroids bigger than Dimorphos. Astronomers used the mission design used in the Tokyo simulation to alter a bigger asteroid's course.
For any potentially hazardous asteroids that would be at least 10 years from impacting Earth, another untested method involves agravity tractor that would hover close to the asteroid for years and impart a small gravitational influence, gradually tugging the rock's course away from Earth.
A nuclear bomb tipped with a spaceship could try to destroy larger asteroids that are threatening. A nuclear vehicle, which has not been tested, would park near the asteroid and blow it up. Nuclear bombs have their challenges.
A nuclear weapon could create a number of smaller, still- damaging rocks that will travel toward Earth. The placement of nuclear weapons in space is banned by some agreements, which suggests a country's use of a nuclear weapon to deter an asteroid's impact with Earth would be a treaty violation. An emergency meeting of the UN Security Council could resolve that legal dilemma.
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DART team members install the Didymos Reconnaissance and Asteroid Camera for Optical navigation in June.
NASA has a lot of work to do, including filling in gaps in scientific knowledge about asteroid threats.
The Wide-field Infrared Survey Explorer has helped NASA log over 30,000 near-Earth asteroids to date. Dr. Fast said that only 40 percent of Congress requires NASA to track. It will take about 30 years for NASA to complete the near-Earth asteroid catalog, she said. The launch of a future spaceship with a massive telescope is scheduled for in the year of 2026.
Dr. Fast said that asteroid impacts were the only natural disaster that could be prevented. DART is important to have, but we have to find them before we can do something like it.
Thomas Zurbuchen, NASA's associate administrator for science, said at a news conference on Monday that he was confident that DART's impact would have an effect on the asteroid.
He said the odds were 100 percent. It is very hard to imagine a scenario in which you come with a lot of energy into a body and nothing happens on the other side.
That depends on DART's ability to hit its target.
Ed Reynolds is the DART project manager at the Applied Physics Lab. He acknowledged that there are limitations to DART's onboard sensors, and that it could go off course.
If it fails to connect with Dimorphos, the spaceship will have less than 90 percent of its fuel left, but it could aim for other space rocks.
He said that they are not keeping a list of backup asteroids. The possibility is there.
