The DART Mission and Advancements in Planetary Defense

The Double Asteroid Redirection Test (DART) was NASA's first planetary defense test mission, designed to validate the technologies and methods associated with using a kinetic impactor to deflect asteroids that pose a threat to Earth. On September 26, 2022, DART intentionally collided with Dimorphos, the moonlet of the near-Earth asteroid Didymos. Observations over the following weeks and months confirmed that DART's impact changed Dimorphos's orbit around Didymos, reducing its speed by 2.6 mm $/$ s. In addition, the DART impact provided the opportunity to observe the creation and evolution of the resulting ejecta, to investigate the dynamics within a perturbed binary system, and to study a natural-scale asteroid impact experiment. Additionally, the Didymos-Dimorphos system was the first binary near-Earth asteroid system investigated by spacecraft, and Dimorphos is the smallest asteroid visited by spacecraft to date. We detail the science and planetary defense findings of DART and look to future advancements. ▪ NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, autonomously navigating to impact the asteroid Dimorphos on September 26, 2022. ▪ DART's successful planetary defense test validated that the kinetic impactor (KI) technique is a viable means to alter an asteroid's future path, which could potentially be used to prevent a future Earth impact. ▪ Analysis of the DART impact event and the resulting aftermath showed that the efficiency of the deflection achieved by the KI technique depended on the asteroid's properties. ▪ Prior information about the asteroid and its properties, such as by a reconnaissance mission, has the potential to allow optimization of the KI technique for asteroid deflection. ▪ Warning time is key for utilizing the KI technique to prevent a potential Earth impact, stressing the need for a planetary defense strategy that includes searching for asteroids and characterizing them in addition to developing mitigation approaches. ▪ In addition to advancing planetary defense objectives, the DART mission provided the first close-up visit to a binary asteroid system and measurements on the smallest asteroid visited by a spacecraft to date. ▪ The success of the DART mission relied on an interdisciplinary and international team, demonstrating the value of wide-ranging cooperation for planetary defense efforts.