NASA’s Double Asteroid Redirection Test (DART): Mutual Orbital Period Change Due to Reshaping in the Near-Earth Binary Asteroid System (65803) Didymos

Abstract The Double Asteroid Redirection Test (DART) is the first planetary defense mission to demonstrate kinetic deflection technique. DART spacecraft will collide with asteroid Dimorphos, smaller component of binary system (65803) Didymos. impact excavate surface/subsurface materials leading formation a crater and/or some magnitude reshaping (i.e., shape change without significant mass loss). ejecta may eventually hit Didymos’s surface. If energy delivered surface high enough, also occur in Didymos, given its near-critical spin rate. Reshaping on either body modify mutual gravitational field, reshaping-induced orbital period change, addition impact-induced change. left unaccounted for, this could lead an erroneous interpretation effect Here we report results full two-body problem simulations that explore how influences dynamics. In general, find becomes shorter linearly increasing magnitude. shortest axis shrinks by ∼0.7 m, or Dimorphos’s intermediate ∼2 would be comparable Earth-based observation accuracy, ∼7.3 s. Constraining decouple reshaping- and changes; constrained observing while likely difficult constrain but investigated ESA's Hera visit Didymos late 2026.