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Lunar and Planetary Laboratory & Department of Planetary Sciences | The University of Arizona
The DART mission is NASA's demonstration of kinetic impactor technology, impacting an asteroid to adjust its speed and path. DART will be the first-ever space mission to demonstrate asteroid deflection by kinetic impactor.
DART's target is the binary asteroid system Didymos, which means "twin" in Greek (and explains the word "double" in the mission's name). Didymos is the ideal candidate for humankind's first planetary defense experiment, although it is not on a path to collide with Earth and therefore poses no actual threat to the planet. The system is composed of two asteroids: the larger asteroid Didymos (diameter: 780 meters, 0.48 miles), and the smaller moonlet asteroid, Dimorphos (diameter: 160 meters, 525 feet), which orbits the larger asteroid. Currently, the orbital period of Dimorphos around Didymos is 11 hours and 55 minutes, and the separation between the centers of the two asteroids is 1.18 kilometers (0.73 miles). The DART spacecraft will impact Dimorphos nearly head-on, shortening the time it takes the small asteroid moonlet to orbit Didymos by several minutes.
The Didymos system is an eclipsing binary as viewed from Earth, meaning that Dimorphos passes in front of and behind Didymos as it orbits the larger asteroid as seen from Earth. Consequently, Earth-based telescopes can measure the regular variation in brightness of the combined Didymos system to determine the orbit of Dimorphos. After the impact, this same technique will reveal the change in the orbit of Dimoprhos by comparison to measurements prior to impact. The timing of the DART impact in September 2022 was chosen to be when the distance between Earth and Didymos is minimized, to enable the highest quality telescopic observations. Didymos will still be roughly 11 million kilometers (7 million miles) from Earth at the time of the DART impact, but telescopes across the world will be able to contribute to the global international observing campaign to determine the effect of DART's impact.
Research ProfessorDeputy Principal Investigator, OSIRIS-APEX
Research ScientistPrincipal Investigator, Spacewatch