What could we do if we saw a dangerous asteroid on a collision course with our planet? NASA has an idea it’s testing, though it may sound like a Hollywood plot. The dart mission will deliberately fly a small spacecraft toward an asteroid to see if its trajectory can be diverted. The idea is to test whether this concept would be effective if a really dangerous asteroid were observed heading towards Earth.
The DART spacecraft launched in November last year and sent back its first images in December. But following the spacecraft is only half the picture, as the NASA team also needed to confirm the exact orbit of the asteroid they are targeting.
Asteroid Dimorphos is one of a binary pair, along with its larger companion Didymos. They orbit the Sun in about two years, in an eccentric orbit that at some points is as close to the Sun as Earth is, and at other points is 2.3 times as far from the Sun. The DART researchers needed to confirm the exact orbit of asteroids to make sure the spacecraft intercepted them correctly, which they did by using observations in early 2021.
But beyond this, it was also important for the team to have an accurate model of how the asteroid system behaved before the spacecraft hit it. So more observations were made using ground-based telescopes in July this year.
“The before-and-after nature of this experiment requires exquisite knowledge of the asteroid system before we do anything to it,” explained Nick Moskovitz, an astronomer at Lowell Observatory who worked on the observing campaign, in an release. “We don’t want, at the last minute, to say, ‘Oh, here’s something we hadn’t thought of or phenomena we hadn’t considered.’ We want to be sure that any change we see is entirely due to what DART did.”
Thanks to these latest observations, the team has confirmed the movement of the binary asteroid system, when it could see events called mutual events when one asteroid passed in front of the other. The researchers looked at 11 mutual events that allowed them to model where the two asteroids will be in relation to each other when the DART spacecraft impacts Dimorphos.
“We’re really very confident now that the asteroid system is well understood and we’re prepared to understand what happens after impact,” Moskovitz said.