DART: Everything you need to know about NASA's asteroid deflection mission

DART: Everything you need to know about NASA’s asteroid deflection mission

NASA isn’t just about sending robots to Mars and building space telescopes. They are also testing plans for protecting our planet in the event we spot an asteroid or comet on a collision course with Earth. A large part of these plans, of course, surveys the sky for potentially dangerous objects. But that’s not all: the planetary defense program also includes a mission called DART.

First things first: There is no asteroid on a collision course with Earth. We’re not going down the path of the dinosaurs yet. The goal of the DART mission is to prepare us. What would we do if we found a dangerous space rock coming our way? And can we be sure that our plan will work?

NASA has no plans to blow up a dangerous asteroid like Bruce Willis Armageddon. Instead, the idea behind the DART mission was to crash a spacecraft on it and put it in a safer orbit.

And that is exactly what NASA did on September 27, 2022 at 00:14 BST. The DART spacecraft successfully crashed into its target asteroid, Dimorphos.

Here’s everything you need to know about the first-of-its-kind mission.

What is the DART mission?

The Double Asteroid Redirection Test (DART) mission is a test of NASA’s planetary defense plans. It is part of the Asteroid Impact and Deflection Assessment (AIDA) mission, a joint collaboration between ESA, NASA, the German Aerospace Center (DLR), the Observatoire de la Côte d’Azur (OCA) and the Applied Physics Laboratory (JHU) of Johns Hopkins University ) /APL).

What is a potentially dangerous item?

An asteroid or comet over 140 meters in diameter approaching Earth at a distance of less than 5 percent of the distance from Earth to the Sun is called a “potentially hazardous object” (PHO). Most of these will pose no threat to us — in fact, NASA says none of the known PHOs have a significant chance of hitting Earth in the next 100 years. However, it estimates that only 40 percent of these objects are known.

In case we should spot a PHO heading straight for Earth, NASA has a plan: use a spacecraft to deflect the oncoming asteroid. DART is the first attempt to do just that, using a near-Earth binary asteroid called Didymos. Orbiting Didymos is a small moon called Dimorphos, which the spacecraft successfully ejected into a different orbit in September 2022.

What is the goal of the DART mission?

DART is the first-ever mission to attempt to reverse the path of an asteroid by having a spacecraft crash into it.

The mission is part of NASA’s planetary defense strategy and aims to build on our ability to model, predict and prepare for an asteroid that could pose a threat to Earth should one be discovered.

It was launched on November 23, 2021 on a SpaceX Falcon 9 rocket from Vandenberg Space Force Base, California and hit on September 27, 2022.

“It’s essentially a big science experiment to see if crashing a spacecraft into an asteroid is a good way to change its orbit around the Sun and possibly deflect an Earth-crossing asteroid in the future, should that happen, or rather, when this happens,” said cosmochemist and author of meteorite dr Tim Gregory.

“It sounds impossible that something as light as a spacecraft, even a spacecraft like DART that weighs more than half a ton, could possibly bump into something like an asteroid that weighs millions of tons. But you don’t have to nudge an asteroid very far for it to miss Earth entirely. Just fractions of a degree and you will miss Earth by millions of kilometers.”

More like that

© NASA/Johns Hopkins APL

Which asteroid did DART crash on?

DART’s target was a binary asteroid system consisting of a larger asteroid named Didymos, which is Greek for “twin,” and a smaller companion asteroid named Dimorphos, which is Greek for “two forms,” ​​orbiting it approximately every 12 hours. Didymos is about 780 m in diameter and Dimorphos is about 160 m in diameter.

“It is important to emphasize that this particular asteroid system poses no threat to Earth. It was simply chosen as a target for this science experiment, and it was chosen from a few different candidates because of its orbit around the sun,” Gregory said.

The spacecraft collided with Dimorphos when it was about 11 million kilometers from Earth. At the time of impact, the speed was estimated at about 6.6 km/s.

Is it safe?

Yes, the DART mission is safe. Didymos, the target asteroid, is not a threat to Earth. When DART reached the asteroid in 2022, it was about 11 million kilometers away, and the goal was only to put the moon Dimorphos in a different orbit around the asteroid.

What’s on board DART?

© NASA/Johns Hopkins APL/Ed Whitman

DART was designed and built by teams at the Johns Hopkins Applied Physics Laboratory (APL) in Maryland, USA. The main structure is a cube about 1m in diameter, fitted on opposite sides with large, flexible solar arrays, each extending about 8m. It has a mass of around 610 kg.

It is powered by NEXT-C, NASA’s Evolutionary Xenon Thruster-Commercial, a solar-powered ion propulsion system that produces thrust using xenon as fuel.

On board is a high-resolution camera DRACO or Didymos Reconnaissance and Asteroid Camera for Optical navigation. In addition to aiding in navigation, the camera was also used to measure the size and shape of the asteroid target to study the geology of the impact site. Images captured by DRACO prior to the kinetic impact were streamed back to Earth in real time.

For the last four hours prior to impact, SMART Nav, or Small-body Maneuvering Autonomous Real-Time Navigation, worked alongside DRACO to autonomously maneuver the spacecraft into position for impact.

The spacecraft also carried a companion CubeSat called LICIACube (Light Italian CubeSat for Imaging of Asteroids), designed by Agenzia Spaziale Italiana (ASI). LICIACube was deployed on Sep 11 during the spacecraft’s approach to Dimorphos and captured images of the impact.

How did you direct DART?

NASA used the “kinetic impactor” technique – meaning the spacecraft crashed into the asteroid to change its course.

DART maneuvered using its onboard camera, DRACO, and autonomous navigation software. These steered the spacecraft to collide with Dimorphos at a speed of about 6.6 km/s (14,700 mph), altering the small moon’s speed by less than 1 percent.

What happens now after the collision?

After impact, the DART investigation team will compare the results of the spacecraft’s collision with Dimorphos, through observations made with ground-based telescopes, to sophisticated computer simulations they have already run. In this way, they will be able to assess the effectiveness of kinetic impact and determine the most effective way to deploy it should future planetary defense scenarios arise.

“The essence of any kind of science is that sometimes you just don’t know what’s going to happen,” Gregory said.

“And since this mission is the first of its kind, I think the scope for success is huge. And I think, to paraphrase the Apollo astronauts, hopefully it will be a success, but it could be a very successful failure.”

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