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On Monday, a NASA spacecraft will intentionally crash into an asteroid called Dimorphos.
The Double Asteroid Redirection Test Mission (DART) aims to see if this type of kinetic impact can help deflect an asteroid that poses a threat to Earth.
“We’re moving an asteroid,” said Tom Statler, NASA program scientist for the DART mission. “We change the movement of a natural celestial body in space. Mankind has never done that before.”
Here’s what you need to know about this mission.
The DART spacecraft is about the size of a school bus. Since launching in November 2021, it has been on course to reach its asteroid destination. The spacecraft will arrive in the asteroid system on September 26th. Impact is expected at 7:14 p.m. ET.
The spacecraft is heading for a binary asteroid system in which a tiny “moon” asteroid called Dimorphos orbits a larger asteroid, Didymos.
Didymos. which means “twin” in Greek is approximately 780 meters (2,560 feet) In diameter. Meanwhile, Dimorphos measures 525 feet (160 meters) 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 kilometers).
Neither Dimorphos nor Didymos are Danger of collision with the earth – before or after the collision.
DART goes down in radiance. It will target Dimorphos, accelerate to 13,421 miles per hour (21,600 kilometers per hour) and crash almost head-on into the moon.
The spacecraft is about 100 times smaller than Dimorphos, so it won’t wipe out the asteroid.
Instead, DART attempts to change the asteroid’s speed and path in space. The mission team likened this collision to a golf cart crashing into one of the Great Pyramids – enough energy to leave an impact crater in its wake.
The impact changes Dimorphos’ speed by 1% while orbiting Didymos. It doesn’t sound like much, but it will change the moon’s orbital period.
The nudge will displace Dimorphos slightly and gravitationally bind it more tightly to Didymos — so the collision will not alter the binary system’s path around Earth or increase its chances of becoming a threat to our planet.
The spacecraft will share its view of the binary asteroid system through an instrument known as the Didymos Reconnaissance and Asteroid Camera for Optical Navigation, or DRACO.
This imager, which will serve as DART’s eyes, will allow the spacecraft to identify the binary asteroid system and distinguish which space object it is meant to hit.
This instrument is also a high-resolution camera aiming to capture images of the two asteroids, which will be streamed back to Earth at a rate of one frame per second in what will look almost like video. You can watch the live stream on NASA websitebeginning at 6 p.m. ET Monday.
Didymos and Dimorphos will appear as stings of light about an hour before impact, gradually growing larger and more detailed in the image.
Dimorphos has never been observed before, allowing scientists to finally grasp its shape and what its surface looks like.
We should be able to see Dimorphos in exquisite detail before DART crashes into it. Given the time it takes for images to be streamed back to Earth, they are visible for eight seconds before signal loss occurs and DART’s mission ends – if successful.
The spaceship too has his own photojournalist with him on the trip.
A briefcase-sized satellite belonging to the Italian Space Agency hitchhiked into space on DART. Dubbed the Light Italian CubeSat for Imaging of Asteroids, or LICIACube, the satellite separated from the spacecraft on Sep 11. The satellite flies behind DART to record what is happening from a safe perspective.
Three minutes after impact, LICIACube will fly past Dimorphos to capture images and video of the impact cloud and maybe even spy on the impact crater. The CubeSat will turn to keep its cameras trained on Dimorphos as it flies by.
While not immediately available, the images and video will be sent back to Earth in the days and weeks following the collision.
The LICIACube will not be the only observer. NASA’s James Webb Space Telescope, Hubble Space Telescope and Lucy Mission will observe the impact. The Didymos system could get brighter as its dust and debris are ejected into space, said Statler, the NASA program scientist.
But ground-based telescopes will be crucial to determine if DART has successfully altered Dimorphos’ motion.
The Didymos system was discovered in 1996, so astronomers have many observations of the system. After the impact, observatories around the world will watch as Dimorphos cruises in front of and behind Didymos.
Dimorphos takes 11 hours and 55 minutes to orbit Didymos once. If DART is successful, that time could shave 73 seconds off, “but we actually think we’re going to change it by about 10 minutes,” said Edward Reynolds, DART project manager at Johns Hopkins University’s Applied Physics Laboratory.
Statler said he would be surprised if a measurement of period change came in less than a few days, but even more if it took longer than three weeks.
“I am very confident that we would strike on Monday and it will be a complete success,” said Lindley Johnson, NASA planetary defense officer.
But if DART misses its proverbial dartboard, the team will be ready to make sure the spacecraft is safe and download all of its intel to find out why it didn’t hit Dimorphos.
The Applied Physics Laboratory’s Mission Operations Center will intervene if necessary, although DART has been operating autonomously for the last four hours of its journey.
It takes 38 seconds for a command to get from Earth to the spacecraft, allowing the team to react quickly. The DART team has rehearsed 21 contingency plans, said Elena Adams, DART mission systems engineer at the Applied Physics Lab.
Dimorphos was chosen for this mission because its size is comparable to asteroids that could pose a threat to Earth. An asteroid the size of Dimorphos could wreak “regional devastation” if it hits Earth.
The asteroid system is “the perfect natural laboratory” for the test, Statler said.
The mission will allow scientists to better understand the size and mass of each asteroid, which is crucial for understanding near-Earth objects.
Near-Earth objects are asteroids and comets with an orbit that places them within 30 million miles (48.3 million kilometers) of Earth. Detecting the threat of near-Earth objects that could cause severe damage is a major focus for NASA and other space agencies around the world.
There are currently no asteroids on a direct impact course 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, particularly understanding what kind of force can shift the orbit of a near-Earth asteroid that could collide with our planet.
movies make countering asteroid approaches seem like a hasty scramble to protect the planet, but “That’s not the way to do planetary defense,” Johnson said. Blowing up an asteroid could be more dangerous because its parts could then be on a collision course with Earth.
However, NASA is considering other methods to alter the movement of asteroids.
The DART spacecraft is believed to be a kinetic impactor that could change the speed and path of Dimorphos. If DART is successful, it could be an asteroid deflection tool.
Another option is a gravity tractor, which relies on the mutual gravitational pull between a spacecraft and an asteroid to pull the space rock from its impacting trajectory to a more benign one, Johnson said.
Another technique is ion beam deflection, or bombarding an asteroid with an ion thruster for long periods of time until the ions change the asteroid’s velocity and orbit.
But both take time.
“Any technique you can think of that changes the orbital velocity of the 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 what could best be deflected based on an asteroid’s size and trajectory.
Finding populations of dangerous asteroids and determining their size are priorities for NASA and its international partners, Johnson said. The design for a space-based telescope called Near-Earth Object Surveyor Mission is currently being reviewed.
The Didymos system will not be lonely for long. To study the aftermath of the impact, the European Space Agency’s Hera mission will launch in 2024. The spacecraft, together with two CubeSats, will reach the asteroid system two years later.
Hera will study both asteroids, measure the physical properties of Dimorphos, and study the DART impact crater and moon’s orbit to develop an effective planetary defense strategy.