A new age of planetary defense: NASA’s DART mission succeeds 


Photo from nasa.gov

Blaise Puscavage, Contributor

NASA successfully completed its Double Asteroid Redirection Test (DART) mission on Sept. 26, in what the agency’s chief Bill Nelson is calling a “watershed moment for planetary defense and a watershed moment for humanity.” 

DART was launched on Nov. 24, 2021, and was designed by the Johns Hopkins Applied Physics Laboratory and SpaceX technology. Its main target was a non-threatening, binary asteroid system called “Didymos.” The Didymos system is comprised of two main asteroids: Didymos, the larger asteroid located in the center of the binary system, and Dimorphos, the smaller “moon” which orbits around Didymos. Didymos orbits around the Sun while Dimorphos, orbits around the main asteroid simultaneously. The binary system was first discovered in 1996 and was labeled as a “potentially hazardous asteroid,” but it posed no immediate threat to Earth even at its closest. 

The DART mission lasted 10 months and one day and concluded with a direct impact of the DART rocket into Dimorphos at roughly 14,000 miles per hour, all captured on a live stream with photos taken from both DART and the LICIACUBE, which was launched from the rocket before impact. The hope of the mission was simple: to make an impact and slightly change the orbit of Dimorphos around Didymos. The DART investigation has found some change in Dimporphos’ orbit, which marks the first time humanity has ever intentionally changed the motion of a celestial object in space. 

The Pace Press had the opportunity to speak with Dawn Graninger, Johns Hopkins University Applied Physics Laboratory Physicist and member of the DART investigation team.

NASA has successfully completed its historic DART mission, marking a huge turning point for planetary defense. One of the first questions that come to mind is why now? Was there an event or conversation that really sparked the heightened interest in planetary defense? 

So the DART mission has been in the works for about eight years. It takes a while to build a spacecraft and planetary defense and has sort of always been around and on the radar–so over eight years we’ve been building this. What’s really special, though, about the timing of DART, was it was the right time for the right objects. DART went to a binary asteroid system. And so when people were thinking about designing the mission and saying, ”What do we do and what asteroid do we want to target?” the Didymos system came up in conversations and they said, ”Oh, this might work out pretty well.” And what was really special was that the Didymos system was sort of very close to Earth in a way that was very easily observable, so when we impacted on Dimorphos, the Moon of Didymos, we would be able to get those observations we need to constrain the orbit or the change in the moon’s orbit around the larger asteroid. 

What was most fascinating when researching the DART mission was the attention to detail that went into this mission. Everything was seemingly calculated down to the millisecond to make an impact with Dimorphos. What were some of the logistical challenges that came with such attention to detail? 

I think one of the first challenges is that you’re taking this spacecraft and you’re trying to hit [Dimorphos], a 160-meter object that is very far away [while] your spacecraft is going 13,000 miles an hour. So, one of the developments that were made for DART was something called Smart NAV. Smart NAV is actually the guidance system that drove DART into Dimorphos. It had all of this autonomous correction, it did all the autonomous tracking. Four hours before impact, we basically handed the keys over to the spacecraft and said, all right, DART, you’re on your own now, it’s time to hit the asteroid. There were opportunities to tweak parameters and we see now that we can see the asteroid because we had no idea what it really looked like before. You know, now that we see, oh, maybe we need to update this parameter so that we get the perfect hit. But at the end of the day, it wasn’t somebody driving in the spacecraft, it was really this autonomous algorithm.

NASA has stated that Didymos was the “perfect candidate” for this mission. Although the binary asteroid system posed no threat to Earth, what made this system so special for the DART mission? 

So, what was really special about it was the fact that it was two. And so you have this larger [asteroid] Didymos and Dimorphos going around it. And because there were two asteroids, through different observational techniques before impact, people had been studying the system and they knew exactly how long it took for that moon to go around Didymos. So what that meant was that when we impacted Dimorphos and we changed its orbit, we had all that pre-data. We knew how long it took before, so we can very accurately say, well, this is how much we were able to change it. And it was just a very unique opportunity. Other than that, I mean, it was just the right target at the right time.

We have long seen the threat of a massive life-threatening asteroid hitting Earth through media with movies like “Armageddon” or even more recently, “Don’t Look Up.” Though those movies are fun to watch, the actuality of a Texas-sized asteroid hitting earth seems unfathomable at the current point in time. What may some of the very real implications of this mission look like in terms of planetary defense in the near or distant future? 

Didymos and Dimorphos were never a threat to Earth. The impacts could never have made them a threat to Earth. And we really, and for the next hundred years, don’t know of any threats that are going to be impacting Earth from a detection standpoint. You know, it’s always funny, you mention those movies and they talk about these huge asteroids coming out of nowhere. We know where the asteroids that are in the kilometer size are. We know where all of those are. They’re very big. They’re very easy to see. So that’s what the T in DART stands for, to really test this mitigation method. So within planetary defense, if we were to see an asteroid coming, previously we sort of only thought about these methods. I run simulations and say, this is how much I think I would deflect it until you actually do that test. It’s really hard to get that sort of ground truth data. So the implications really are that it just helps provide that crucial test data that we need for full scale. We can run experiments in a lab, but you know, that’s probably the size of like a ping pong ball impacting into like some rubble on the ground, but not really the same thing as a 20 meters size spacecraft impacting into an asteroid. Just the fact that it is full-scale provides critical data that we can use if we did see something coming and needed to use a kinetic impact.

We have seen several advancements made by NASA in terms of space exploration as a whole over recent years. Now that DART has been completed and was a success, what is next in terms of planetary defense? Do you think we will see another mission similar to DART on a larger scale? 

In terms of what’s next for planetary defense-type missions, there is a mission called the NEO Surveyor and that is a telescope that will hopefully be launched in this decade. And it’s going to go out and try to detect all the asteroids that are 140 meters and larger. That’s really what’s next, it’s actually very important because you can test a DART and you can say, oh, I can just deflect an asteroid, but it doesn’t really help to know that you can deflect an asteroid if you don’t know that there are asteroids coming. So having the ability to do that and say, I know that there are all these asteroids out there now that we didn’t know were there and that we might maybe or threats maybe they’re not threats. It’s very important in terms of other mitigation missions.

DART is just the beginning of NASA’s new age of planetary defense research. Though there aren’t any new DART–style missions on the horizon, the history of planetary defense is changing before our eyes. The advances made by NASA and labs like the Johns Hopkins Applied Physics Laboratory give both, humanity a greater chance of survival from interstellar objects. and a better understanding of the universe we find ourselves in.