Why will the DART mission crash into an asteroid?  we explain

Why will the DART mission crash into an asteroid? we explain

(CNN) — A NASA spacecraft will deliberately crash into an asteroid called Dimorphos on Monday.

The DART, or Double Asteroid Redirection Test, mission aims to test whether this type of kinetic impact can help deflect an asteroid that poses a threat to Earth.

This illustration shows the DART spacecraft heading towards the asteroid Dimorphos. Credit: John Hopkins APL/NASA

“We’re going to deflect an asteroid,” said Tom Statler, NASA program scientist for the DART mission.

“We are going to change 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.

What is DART?

The DART spacecraft is 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 in the asteroid system on September 26. Impact is expected at 7:14 p.m. (Miami time).

Where is he going ?

The spacecraft is heading towards a dual asteroid system, where a small “lunar” asteroid, called Dimorphos, orbits a larger asteroid, Didymos.

Didymos, which means “twin” in Greek, is about 780 meters in diameter. Meanwhile, Dimorphos is about 160 meters in diameter, and its name means “two forms”.

At the time of impact, Didymos and Dimorphos will be relatively close to Earth, about 11 million kilometers away.

Neither Dimorphos nor Didymos pose a risk of collision with Earth, either before or after the mission.

What will DART do?

DART will have a heroic ending: it will target Dimorphos, accelerate to around 13,000 miles per hour, and crash into the moon almost head-on.

The ship is about 100 times smaller than Dimorphos, so it is not capable of destroying the asteroid.

Instead, DART will attempt to alter its speed and trajectory. The mission team compared this collision to that of a golf cart hitting one of the Great Pyramids: barely enough energy to leave an impact crater.

The impact will change the speed of Dimorphos by 1% while orbiting Didymos. It doesn’t seem like much, but it will change the orbital period of this moon.

The thrust will displace Dimorphos slightly and further tighten its gravitational lock with Didymos, so the collision will not alter the binary system’s trajectory around Earth or increase its chances of becoming a threat to our planet.

What can we see?

The spacecraft will share its view of the twin asteroid system through an instrument known as the Didymos Optical Reconnaissance and Navigation Camera, or DRACO.

This sensor, which acts as the eyes of the DART, will allow the spacecraft to identify the dual asteroid system and distinguish the space object with which it must collide.

This instrument is also a high-resolution camera that aims to capture images of the two asteroids to transmit them to Earth at the rate of one frame per second in what will almost look like video. You can watch the show live at NASA websitestarting at 6:00 p.m. (Miami time) on Monday.

Didymos and Dimorphos will appear as points of light about an hour before impact, gradually becoming larger and more detailed in frame.

Dimorphos has never been observed before, so scientists will finally be able to capture its shape and what its surface looks like.

We should be able to see Dimorphos in detail before DART hits it. Given the time it takes for the images to reach Earth, they will be visible for eight seconds before a loss of signal occurs and the DART mission terminates, if successful.

The ship also has its own photojournalist.

A briefcase-sized cubic satellite provided by the Italian Space Agency accompanied DART on its journey into space. Named LICIACube (Light Italian CubeSat for Imaging of Asteroids), it separated from the spacecraft on September 11. The satellite moves behind DART to record events from a secure location.

Three minutes after impact, LICIACube will fly alongside Dimorphos to capture images and video of the impact and possibly even spy on the crater it creates. The CubeSat will rotate to keep its cameras pointed at Dimorphos during its flight.

Images and video will not be available immediately, but will be transmitted to Earth in the days and weeks following the collision.

How will we know if the mission was successful?

The LICIACube will not be the only observer. The James Webb Space Telescope, Hubble Space Telescope and NASA’s Lucy Mission will observe the impact. The Didymos system could glow when dust and debris are ejected into space, said Statler, the NASA program scientist.

But ground-based telescopes will be key to determining whether DART succeeded in altering Dimorphos’ trajectory.

The Didymos system was discovered in 1996, so astronomers have many observations of the system. Following the impact, observatories around the world will see Dimorphos crossing ahead and moving behind Didymos.

Dimorphos takes 11 hours and 55 minutes to complete one orbit of Didymos. If DART is successful, that time could drop by 73 seconds, “but we actually think we’re going to change it by about 10 minutes,” said Edward Reynolds, DART project leader at the Johns Hopkins University Applied Physics Laboratory. .

Statler noted that he would be surprised if the measurement of the period change happened in less than a few days, but even more so if it took longer than three weeks.

What if DART fails and doesn’t hit the asteroid?

“I’m very confident that we’re going to strike on Monday, and it will be a complete success,” said Lindley Johnson, NASA’s head of planetary defense.

But if DART misses its proverbial target, the team will be ready to make sure the spacecraft is safe and download all of its data to find out why it didn’t hit Dimorphos.

The Applied Physics Laboratory’s Mission Operations Center will step in if necessary, although DART has been operating autonomously for the last four hours of its journey.

It takes 38 seconds for an order to travel from Earth to the ship, so the team can react quickly. The DART team has 21 rehearsed contingency plans, explained Elena Adams, DART mission systems engineer at the Applied Physics Laboratory.

Why do we need to test this and why on this asteroid?

Dimorphos was chosen for this mission because it is comparable in size to asteroids that could pose a threat to Earth. A Dimorphos-sized asteroid could cause “regional devastation” if it collides with Earth.

The asteroid system is “the perfect natural laboratory” for the test, Statler said.

The mission will give scientists a better understanding of the size and mass of each asteroid, which is crucial for understanding near-Earth objects (NEOs).

Near-Earth objects are asteroids and comets whose orbit places them within 30 million kilometers of Earth. Detecting the threat posed by near-Earth objects with the potential to cause serious damage is one of the primary goals of NASA and other space organizations around the world.

No asteroids are currently on a direct impact path with Earth, but there are over 27,000 near-Earth asteroids of all shapes and sizes.

The valuable data gathered by DART will help in planetary defense strategies, especially to understand what kind of force can shift the orbit of a near-Earth asteroid that could collide with our planet.

Why not just blow up the asteroid, like in “Armageddon”?

The movies make the fight against asteroids a hasty battle to protect the planet, but “that’s not the way to defend the planet,” Johnson said. Blowing up an asteroid could be more dangerous because its pieces could then collide with Earth.

However, NASA is considering other methods to alter the trajectory of asteroids.

The DART spacecraft is believed to be a kinetic impactor that could alter the speed and trajectory of Dimorphos. If DART is successful, it could be a tool to deflect asteroids.

Another option is a gravity tractor, which relies on the mutual gravitational attraction between a spacecraft and an asteroid to pull space rock off its impact path and onto a more benign path, Johnson said.

Another technique is ion beam deflection, i.e. firing an ion engine on an asteroid for long periods of time until the ions change the speed and orbit of the asteroid. .

But both techniques take time.

“Any technique you can think of that changes the orbital velocity of the orbiting asteroid is a viable technique,” Johnson said.

An international forum called the Space Planning Commission brought together 18 national space agencies to assess what would be best to deflect an asteroid, based on its size and trajectory.

Finding populations of dangerous asteroids and determining their size are top priorities for NASA and its international partners, Johnson noted. The design of a space telescope called Near-Earth Object Surveyor Missionknown in Spanish as the Near-Earth Object Surveillance Mission.

Will other spacecraft pass through Dimorphos in the future?

The Didymos system will not remain alone for long. The European Space Agency’s Hera mission will be launched in 2024 to study the consequences of the impact. The spacecraft, along with two CubeSats, will arrive in the asteroid system two years later.

Hera will study the two asteroids, measure the physical properties of Dimorphos, and examine the DART impact crater and the moon’s orbit, with the goal of establishing an effective planetary defense strategy.

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