Asteroids. These space rocks are remnants of the first days of our solar system. Agencies around the world are working to bring samples back, like NASA’s Osiris-ReX and JAXA’s Hayabusa-2 because bringing a piece back is like looking into a time capsule from the universe. But asteroids pose a serious threat to Earth. And ESA and NASA have a unique plan to combat that particular problem: they’re going to slam a spacecraft into an asteroid. DART mission.
There were several wide concepts, like going out and paint an asteroid white or black to change its thermal radiation, or trying to capture with a net and attaching some engines. After 15 years, scientists agree that the best and simplest way is actually to hit an asteroid with a spacecraft at high velocity.
So, Hera and DART are really the result of the scientific process over almost two decades. The scientific collaboration of these two missions is known as the Asteroid Impact and Deflection Assessment or AIDA. NASA’s will go first, with its Double Asteroid Redirection Test or DART mission. In 2022, DART will be the one to smash into an asteroid and help the AIDA mission to study how effective a kinetic impactor would be in asteroid deflection.
Four years after DART’s impact, ESA’s Hera probe will arrive to assess the effects of this hypervelocity impact and provide a clear post-mortem of DART’s impact. Now, you might be wondering why four years later? Won’t that be too late? Well, in a 2005 NASA mission, its Deep Impact spacecraft shot a copper impactor at a comet, hoping to capture the immediate collision. Unfortunately, onboard cameras were clouded by millions of kilograms of debris. It wasn’t until 2011, that another spacecraft was able to capture the aftermath.
So…let’s just say that NASA and ESA learned their lesson. So which asteroid is the lucky target? Well, there are hundreds of thousands of them, but one pair in particular stood out: Didymos. It’s an ideal candidate because it’s in a binary asteroid system, so there isn’t just one asteroid, but two asteroids orbiting each other. Using a binary asteroid is very important because scientists can test the deflection from DART a lot more easily because the smaller orbiting asteroid moves slower than an isolated one.
While Didymos is the larger one, at around 780 meters in diameter, the main attraction is the smaller Deemorfus. At about 160 meters across, Dimorphos is perfect since it’s a more typical size of an asteroid that could threaten Earth. And just to put that into perspective, that’s about the size of the Great Pyramid of Giza. So we actually have no idea what is its composition, what is its structure.
This is something we really need to understand to have a good interpretation of the results of the DART impact. So to do that job, after DART’s impact, Hera will have a suite of instruments aboard to probe Dimorphos. Firstly, Hera will test out its autopilot technology to get close to the asteroid’s surface. Using ground penetrating radar, the spacecraft will be able to see its internal structure, similar to taking an X-ray of an asteroid. One of the main instruments onboard is the asteroid framing cameras, which will capture the topology and surface structure, while a thermal infrared instrument will provide data on the strength of the surface material.
There’s also a gravimeter, which will measure the gravity field. Hera will also have two CubeSats, and it will be the first time that ESA takes these mini satellites into deep space. The first will focus on low-frequency radar to probe the interior structure, while the second is a multi-spectral imager that will get data in different wavelengths to understand the composition of the asteroid. So when can we expect to see this mission take off? Well, DART is expected to launch in July 2021 on a SpaceX Falcon 9, while Hera will launch in October 2024 on an ArianeSpace Ariane 6. The spacecraft will make multiple flybys around the asteroid, taking pictures and measurements with each one.
And as it gets closer, Hera will release the two CubeSats that will venture very close to the surface until July 2027, when the mission will come to an end. But really though, what is the likelihood of an asteroid actually hitting Earth? The question is when, but one day it will happen. And the good thing about asteroids is that by monitoring the sky, not only we can predict, when this will happen, but we can also do something about it. So rest assured though, Dimorphos poses no threat to us earthlings. But that’s why gathering all the data now is so crucial to help us be better prepared for when that day may possibly come.