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On Monday, a NASA spacecraft will deliberately collide with an asteroid called Dimorphos.
The purpose of the Double Asteroid Redirection Test mission, or DART, is to see if these types of kinetic effects can help deflect asteroids that pose a threat to Earth.
“We’re moving an asteroid,” said Tom Stettler, NASA program scientist for the DART mission. “We are changing the motion of a natural celestial body in space. Humanity has never done this before.”
Here’s what you need to know about this mission.
The DART spacecraft is about the size of a school bus. It has been traveling to reach its asteroid target since its launch in November 2021. The spacecraft will arrive at the asteroid system on September 26. Impact is expected at 7:14 PM ET.
The spacecraft is heading toward a double asteroid system, where a smaller “moon” asteroid, named Dimorphos, orbits a larger asteroid, Didymos.
Didymos, meaning “twin” in Greek, is about 2,560 feet (780 m). Dimorphos, meanwhile, measures 525 feet (160 m) in diameter, and its name means “two forms”.
At the time of impact, Didymos and Dimorphos will be relatively close to Earth – within 6.8 million miles (11 million km).
Neither is Dimorphos nor Didymos. In danger of hitting the ground – before or after a collision.
DART is going down in a blaze of glory. It will set its sights on Dimorphos, accelerate to a speed of 13,421 mph (21,600 km/h) and crash into the moon.
The spacecraft is about 100 times smaller than Dimorphos, so it won’t obliterate the asteroid.
Instead, DART will attempt to change the asteroid’s speed and path in space. The mission team compared the collision to a golf cart crashing into one of the Great Pyramids — enough energy to leave an impact crater.
This effect will change Dimorphos speed by 1% as it orbits Didymos. It doesn’t seem like much, but doing so will change the Moon’s orbital period.
The shock will slightly alter Dimorphos and bind it more gravitationally to Didymos – so the collision won’t change the binary system’s path around Earth or increase its chances of posing a threat to our planet.
The spacecraft will share its view of the dual asteroid system with an instrument known as the Didymos Reconnaissance and Asteroid Camera, or DRACO, for optical navigation.
This imager, which acts as DART’s eyes, will allow the spacecraft to identify the binary asteroid system and distinguish which spacecraft it needs to attack.
The instrument is also a high-resolution camera intended to capture images of the two asteroids returning to Earth at a rate of one image per second, which will appear almost like a video. You can watch the live stream. NASA websitebeginning Monday at 6 p.m. ET.
Didymos and Dimorphos will appear as wings of light about an hour before impact, growing progressively larger and more detailed in the frame.
Dimorphos had never been observed before, so scientists could finally deduce its shape and its surface appearance.
We should be able to see Dimorphos in stunning detail before the dart hits him. Given the time it takes for the images to return to Earth, they will be visible for eight seconds before the signal is lost and DART’s mission ends – if it succeeds.
Spaceships too He has his own photojournalist along for the ride.
A briefcase-sized satellite from the Italian Space Agency traveled into space with DART. Called the Light Italian CubeSat for Imaging of Asteroids, or LICIACube, it separated from the spacecraft on September 11. The satellite is traveling behind DART to see what happens from a safe perspective.
Three minutes after impact, LICIACube will fly by Dimorphos to capture images and video of the impact plume. And maybe even spy on Impact Crater. The CubeSat will turn its cameras to fly towards Dimorphos.
Photos and video, while not immediately available, will be returned to Earth in the days and weeks following the collision.
LICIACube won’t be the only observer watching. The impact will be observed by the James Webb Space Telescope, the Hubble Space Telescope and NASA’s Lucy mission. The Didymos system may light up as its dust and debris are ejected into space, said Stettler, a NASA program scientist.
But ground-based telescopes will be key in determining whether DART successfully retraces Dimorphos’ motion.
The Didymos system was discovered in 1996, so astronomers have plenty of observations of the system. After the impact, observatories around the world will see Dimorphos pass in front of it and go behind Didymos.
Dimorphos takes 11 hours and 55 minutes to complete the orbit of Didymos. If DART is successful, that time could be reduced by 73 seconds, “but we actually think we’re going to change that by about 10 minutes,” said DART project manager at the Johns Hopkins University Applied Physics Laboratory. Edward Reynolds said.
Staller said he would be surprised if the measurement of period change came in less than a few days, but even more so if it took more than three weeks.
“I’m very confident that we’re going to hit Monday, and it’s going to be a complete success,” said Lindley Johnson, NASA’s planetary defense officer.
But if DART loses its proverbial dartboard, the team will be ready to make sure the spacecraft is safe and download all its information to determine if it’s safe. Why didn’t he kill Dimorphos?
The Applied Physics Laboratory’s Mission Operations Center will intervene if necessary, although DART will operate autonomously for the last four hours of its journey.
It takes 38 seconds for a command to travel from Earth to the spacecraft, so the team can react quickly. Elena Adams, a DART mission systems engineer at the Applied Physics Lab, said the DART team has 21 contingency plans that it has practiced.
Dimorphos was chosen for this mission because it is comparable in size to asteroids that could pose a threat to Earth. An asteroid the size of Dimorphos could cause a “regional catastrophe” if it were to hit Earth.
Statler said the asteroid system is the “perfect natural laboratory” for the test.
The mission will allow scientists to gain a better understanding of each asteroid’s size and mass, which is vital for understanding near-Earth objects.
Near-Earth objects are asteroids and comets that have orbits that keep them within 30 million miles (48.3 million km) of Earth. Detecting the threat of near-Earth objects that could cause severe damage is a primary focus of NASA and other space organizations around the world.
No asteroids currently interact directly with Earth, but there are more than 27,000 near-Earth asteroids of all shapes and sizes.
The valuable data collected by DART will contribute to planetary defense strategies, especially understanding what kind of force might change the orbit of a near-Earth asteroid that could hit our planet.
Movies Fighting an asteroid approach seems like a rushed struggle to protect the planet, but “This is not a planetary defense method,” Johnson said. Blowing up an asteroid can be more dangerous because its fragments may then be on a collision course with Earth.
But NASA is considering other ways to alter the asteroid’s motion.
The DART spacecraft is thought to be a dynamic impactor that can alter Dimorphos’ speed and trajectory. If DART is successful, it could be a means of removing asteroids.
Another option, Johnson said, is a gravity tractor, which relies on the mutual gravitational attraction between a spacecraft and an asteroid to pull a space rock into the asteroid above its impact speed.
Another technique is ion beam deflection, or shooting an ion engine at an asteroid for a long time until the ions change the asteroid’s speed and orbit.
But both of them take time.
“Any technique you can imagine that changes the orbital speed of an asteroid in orbit is a viable technique,” Johnson said.
An international forum called the Space Planning Commission has brought together 18 national space agencies to assess how best to deflect an asteroid, depending on its size and trajectory.
Finding hazardous asteroid populations and determining their size are priorities for NASA and its international partners, Johnson said. The design of a space telescope called Near-Earth Object Surveyor Mission Currently under review.
The Didymos system won’t be alone for long. To survey the aftermath of the impact, the European Space Agency’s Hera mission will launch in 2024. The spacecraft, with two cubesats, will arrive at the asteroid system two years later.
HERA will study both asteroids, measure the physical properties of Dimorphos, and examine the orbits of DART’s impact craters and moons, with the goal of establishing an effective planetary defense strategy.