NASA’s ‘Double Asteroid Redirection Test’ (DART), the world’s first full-scale mission to test technology for defending Earth against potential asteroid or comet hazards, launched recently on a SpaceX Falcon 9 rocket from Space Launch Complex 4 East at Vandenberg Space Force Base in California.
Just one part of NASA’s larger planetary defence strategy, DART — built and managed by the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland — will impact a known asteroid that is not a threat to Earth. Its goal is to slightly change the asteroid’s motion in a way that can be accurately measured using ground-based telescopes.
DART will show that a spacecraft can autonomously navigate to a target asteroid and intentionally collide with it — a method of deflection called kinetic impact. The test will provide important data to help better prepare for an asteroid that might pose an impact hazard to Earth, should one ever be discovered.
Kinetic impactDART’s one-way trip is to the Didymos asteroid system, which comprises a pair of asteroids. DART’s target is the ‘moonlet’ Dimorphos, which is about 160m in diameter and orbits Didymos, which is about 780m in diameter; and because Dimorphos orbits Didymos at much a slower relative speed than the pair orbits the Sun, the result of DART’s kinetic impact within the binary system can be measured much more easily than a change in the orbit of a single asteroid around the Sun.
LICIACube, a CubeSat riding with DART and provided by the Italian Space Agency (ASI), 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, ESA’s (European Space Agency) Hera project will conduct detailed surveys of both asteroids, with particular focus on the crater left by DART’s collision and a precise determination of Dimorphos’ mass.
NASA administrator Bill Nelson said: “DART is turning science fiction into science fact. In addition to all the ways NASA studies our universe and our home planet, we’re also working to protect that home, and this test will help prove out one viable way to protect our planet from a hazardous asteroid should one ever be discovered that is headed toward Earth.”
The spacecraft will intercept the Didymos system between 26 Sepember and 1 October 2022, intentionally slamming into Dimorphos at about 6 km per sec. Scientists estimate the kinetic impact will shorten Dimorphos’ orbit around Didymos by several minutes.
Researchers will precisely measure that change using telescopes on Earth. 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.