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DART is NASA's demonstration of an asteroid deflection using a kinetic impactor. The spacecraft launched aboard a SpaceX Falcon 9 on November 24th 2021, on a direct collision with the binary asteroid system Didymos planned for September 26th 2022. By impacting the small moon, Dimorphos, DART's objective was to alter the moon's orbit about the larger asteroid by several minutes. The navigation of a ballistic mission is usually relatively simple. Other than heading to a violent demise, this mission had a number of unconventional aspects which gave the navigation team interesting challenges: a tight propellant budget for part of the mission, no reaction wheels which resulted in a noisy spacecraft with the Nav team having to rely heavily on Delta Differential One-way Ranging measurements to identify off line-of-sight Delta-V, and critical operations in the last 30 days of the mission under a new thrusting control mode regime. Optical navigation was a critical element in the success of this mission, contributing to the determination of the spacecraft and target ephemerides for refined targeting maneuvers. After strategic decisions in the final weeks of the missions, DART could have comfortably hit the larger asteroid, Didymos, which increased the probably of impact with its moon Dimorphos. • DART was NASA's demonstration of an asteroid deflection using a kinetic impactor. • This mission gave the navigation team interesting challenges. • Optical navigation was a critical element in the success of this mission. • DART could have hit Didymos, which increased the probably of impact with its moon. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.12.023 Byline: Masatoshi Hirabayashi (a), Mutsuko Y. Morimoto (b), Hajime Yano (b), Jun'ichiro Kawaguchi (b), Julie Bellerose (b) Keywords: Asteroids, Dynamics; Celestial mechanics; Near-Earth objects; Satellites, Dynamics Abstract: This note discusses the stability of collinear equilibrium points around a rotating system composed of two masses rigidly connected by a massless rod in the case, where the centripetal force outweighs the gravitational force. It is found that a stable region appears at L.sub.1 when the ratio of gravitational to centripetal acceleration is less than 0.125, and that there is always no stable area at L.sub.2 and L.sub.3; the result is applied to the fast rotating Asteroid 2000EB.sub.14. Author Affiliation: (a) Department of Aeronautics and Astronautics, The University of Tokyo, Bunkyo-ku. 113-8656, Japan (b) Japan Aerospace Exploration Agency, JSPEC, Sagamihara 229-8510, Japan Article History: Received 17 April 2009; Revised 15 December 2009; Accepted 16 December 2009

Abstract: The gravity tractor concept is a proposed method to deflect an imminent asteroid impact through gravitational tugging over a time scale of years. In this study, we present mission scenarios and operational considerations for asteroid mitigation efforts involving multiple gravity tractors. We quantify the deflection performance improvement provided by a multiple gravity tractor campaign and assess its sensitivity to staggered launches. We next explore several proximity operation strategies to accommodate multiple gravity tractors at a single asteroid including formation-flying and mechanically-docked configurations. Finally, we utilize 99942 Apophis as an illustrative example to assess the performance of a multiple gravity tractor campaign. [Copyright &y& Elsevier]