An on-orbit demonstration of asteroid deflection is a key test that NASA and other agencies wish to perform before any actual need is present. 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.
Launch Window: opens July 22, 2021
DART Impact: September 27 – October 2, 2022
Illustration of how DART's impact will alter the orbit of Didymos B about Didymos A. Telescopes on Earth will be able to measure the change in the orbit of Didymos B to evaluate the effectiveness of the DART impact.
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 Didymos system is composed of two asteroids: the larger asteroid Didymos A (diameter: 780 meters, 0.48 miles), and the smaller moonlet asteroid, Didymos B (diameter: 160 meters, 525 feet), which orbits the larger asteroid. The DART spacecraft will impact Didymos B nearly head-on, shortening the time it takes the small asteroid moonlet to orbit Didymos A by several minutes.
Didymos is an eclipsing binary asteroid as viewed from Earth, meaning that Didymos B passes in front of and behind Didymos A as it orbits about 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 Didymos B. After the impact, this same technique will reveal the change in the orbit of Didymos B by comparison to measurements prior to impact. The timing of the DART impact in fall 2022 is chosen to minimize the distance between Earth and Didymos to enable the highest quality telescopic observations. Didymos will still be roughly 11 million kilometers (6.8 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.
The DART demonstration has been carefully designed. The impulse of energy that DART delivers to the Didymos binary asteroid system is low and cannot disrupt the asteroid, and Didymos's orbit does not intersect Earth's at any point in current predictions. Furthermore, the change in Didymos B's orbit is designed to bring its orbit closer to Didymos A. The DART mission is a demonstration of capability to respond to a potential asteroid impact threat, should one ever be discovered.
The Discovery Channel Telescope at Lowell Observatory in Arizona, one of the telescopes across the globe that will be used to evaluate the result of the DART impact. (Credit: Lowell Observatory)
The DART mission is being developed and led for NASA by the Johns Hopkins University Applied Physics Laboratory. NASA's Planetary Defense Coordination Office is the lead for planetary defense activities and is sponsoring the DART mission. Partner institutions on DART include NASA Goddard Space Flight Center, NASA Johnson Space Center, NASA Langley Research Center, NASA Glenn Research Center, NASA Marshall Space Flight Center, Jet Propulsion Laboratory, Aerojet Rocketdyne, Lawrence Livermore National Laboratory, Auburn University, University of Colorado, University of Maryland, Northern Arizona University, and Planetary Science Institute. LICIACube is contributed by Agenzia Spaziale Italiana.
DART is part of the international collaboration known as AIDA—Asteroid Impact and Deflection Assessment. AIDA represents the acknowledgment that planetary defense is an international effort and that scientists and engineers around the world seek to solve problems related to planetary defense through international collaborations.
The Hera mission is a part of AIDA and is currently a candidate ESA mission as part of the agency's Space Safety and Security program. Hera would launch in 2024 and arrive at the Didymos system in 2027 to conduct a six-month survey of both asteroids, with a particular focus on the crater left by DART's collision. The two missions, DART and Hera, are being designed and operated independently, but their combination will boost the overall return to a significant degree. NASA's DART mission is fully committed to international cooperation, and Hera team members are full members of the DART team, to contribute to DART's planetary defense investigations and to fully inform Hera's mission.