NASA sends DART to deflect asteroid

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NASA has launched the world’s first full-scale mission to demonstrate a spacecraft’s ability to intentionally collide with and deflect an asteroid.  

In August 2021, DART team members at APL did a final inspection of one of the spacecraft's two roll-out solar arrays (ROSA) Credit: NASA/Johns Hopkins APL/Ed Whitman

Dubbed DART (Double Asteroid Redirection Test), the mission launched yesterday (Wednesday 24 November 2021) on a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California.

Built and managed by the Johns Hopkins Applied Physics Laboratory (APL), DART is heading for Dimorphos, an asteroid that NASA said is not a threat to Earth. DART’s mission is to slightly change the asteroid’s motion in a way that can be measured using ground-based telescopes.

DART will show that a spacecraft can autonomously navigate to a target asteroid and collide with it. In doing so, DART will provide data to help better prepare for an asteroid that might pose an impact hazard to Earth, should one ever be discovered.

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Hitching a ride on DART is the Italian Space Agency (ASI)’s LICIACube, a CubeSat that will be released prior to DART’s impact to capture images of the impact and the resulting cloud of ejected matter. Roughly four years after DART’s impact, the European Space Agency’s Hera project will conduct detailed surveys of the impact, focussing on the crater left by DART’s collision and a precise determination of Dimorphos’ mass.

“At its core, DART is a mission of preparedness, and it is also a mission of unity,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “This international collaboration involves DART, ASI’s LICIACube, and ESA’s Hera investigations and science teams, which will follow up on this ground-breaking space mission.”

DART’s mission is to the Didymos asteroid system, which comprises Dimorphos, a moonlet that is approximately 530 feet (160m) in diameter and Didymos, which is approximately 2,560 feet (780m) in diameter. Dimorphos orbits Didymos at a slower relative speed than the pair orbits the Sun, so DART’s kinetic impact within the binary system can be measured more easily than a change in the orbit of a single asteroid around the Sun.

“We have not yet found any significant asteroid impact threat to Earth, but we continue to search for that sizable population we know is still to be found. Our goal is to find any possible impact, years to decades in advance, so it can be deflected with a capability like DART that is possible with the technology we currently have,” said Lindley Johnson, planetary defence officer at NASA Headquarters. “DART is one aspect of NASA’s work to prepare Earth should we ever be faced with an asteroid hazard.”

The spacecraft will intercept the Didymos system between September 26 and October 1, 2022, crashing into Dimorphos at roughly 4 miles per second (6km per second). NASA believes the kinetic impact will shorten Dimorphos’ orbit around Didymos by several minutes. Researchers will measure that change using telescopes on Earth and their results will validate and improve scientific computer models critical to predicting the effectiveness of the kinetic impact as a reliable method for asteroid deflection.

NASA added that DART’s single instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), will activate around December 2, 2021 and provide first images from the spacecraft. DART will continue to travel just outside of Earth’s orbit around the Sun for the next 10 months until Didymos and Dimorphos will be a relatively close 6.8 million miles (11 million kilometres) from Earth.

A sophisticated guidance, navigation, and control system, working with Small-body Manoeuvring Autonomous Real Time Navigation (SMART Nav) algorithms, will enable DART to identify and distinguish between the two asteroids. The system will then direct the spacecraft toward Dimorphos. This process will all occur within roughly an hour of impact.