The 2,464th Meeting of the Society

October 7, 2022 at 8:00 PM

Powell Auditorium at the Cosmos Club

DART: The Double Asteroid Redirection Test

Protecting Earth from Planetary Impacts

Andrew Cheng & Andrew Rivkin

Applied Physics Laboratory
Johns Hopkins University

Sponsored by PSW Science Member Joe Schulman


About the Lecture

An on-orbit demonstration of asteroid deflection is a key test that NASA and other agencies wish to perform before any actual need presents itself to protect earth from impact with a large space object. The double asteroid redirection test mission (DART) mission is NASA’s demonstration of kinetic impactor technology that has the potential to deflect an object away from an earth-bound trajectory, before it impacts the planet. The aim of DART is to impact an asteroid to adjust its speed and path. DART will be the first space mission to demonstrate asteroid deflection by a kinetic impactor.

DART’s target is a binary asteroid system called Didymos, composed of a larger asteroid, also called Didymos (780 meters in diameter) and smaller “moonlet” asteroid, called Dimorphos (160 meters in diameter) that orbits the larger asteroid, with an orbital period of 11 hours and 55 minutes. The DART spacecraft will impact Dimorphos nearly head-on. The impact should shorten the orbital period several minutes.

The Didymos system is an eclipsing binary as viewed from Earth: Dimorphos passes in front of and behind Didymos as seen from Earth. Earth-based telescopes can observe variations in brightness of the system that allow its orbital period to be accurately determined. Observations of the orbital period before and after impact will allow mission scientists to determine the effect of the impact. Impact has been timed to occur when the distance between Earth and Didymos is at a minimum, about 11 million kilometers, to allow for the best observation of the impact from earth. A global observing campaign will measure the effect of DART’s impact.

About the Speaker

Andrew Chang
Andy Cheng is Chief Scientist for Space Science at the Johns Hopkins Applied Physics Laboratory (APL), and he is co-lead investigator for the Double Asteroid Redirection Test (DART).

He previously served as Deputy Chief Scientist for Space Science in NASA’s Science Mission Directorate, he was the Project Scientist for the NEAR mission, and he served as Orbital LIDAR scientist on the Joint Science Team for the Japanese Hayabusa mission to asteroid Itokawa. He also was a scientist on the Galileo mission, a co-investigator on the Cassini mission, and the principal investigator for the Long Range Reconnaissance Imager (LORRI) on the New Horizons mission. He joined APL in 1983, and founded the Planetary Exploration Group there in 2004.

Andrew earned a BS in Physics at Princeton University and a PhD in Physics at Columbia University.

Andrew S. Rivkin
Andy Rivkin is a Planetary Astronomer at the Johns Hopkins University Applied Physics Laboratory and Investigation Lead for the Double Asteroid Redirection Test. His research centers on near-infrared spectroscopy and spectrophotometry of asteroids. In addition to observational work, he has been active in the broader Near-Earth Object community, serving as a team member on several efforts to understand and report Earth impact hazards and how to mitigate them. He also leads a group studying and reporting to NASA about the most important unknown factors related to human exploration of an asteroid.

Asteroid 13743 was named for him, in recognition of his work.

He earned a PhD in Planetary Sciences from the University of Arizona.