In the mid of 2021, NASA's Double Asteroid Redirection Test (DART) mission will be launched, starting its journey towards binary asteroid (65803) Didymos. In autumn 2022, DART (with a total mass of ~650 kg) will be the first space mission demonstrating the kinetic impactor technique for planetary defense by impacting Dimorphos, the 164±18 m-size secondary, with a speed of ~6.6 km/s. Such impact is expected to form a crater and a dense ejecta plume that will propagate rapidly in the near-by asteroid environment. While DART will be impacting Dimorphos, the Light Italian CubeSat for Imaging of Asteroids (LICIACube) (to be released from DART ten days before the impact) will both image the expanding plume and reveal the surface changes/processes that will occur after the impact. LICIACube will provide multiple images of the target down to a minimum distance of ~55 km from Dimorphos. The LICIACube narrow- and wide-angle cameras - LEIA (LICIACube Explorer Imaging for Asteroid) and LUKE (LICIACube Unit Key Explorer), respectively – will capture the post-impact processes and therefore describe the in-situ events, such as the newly formed crater, the expanding slow (<5 m/s) ejecta and the dynamics of its plume. In particular, LICIACube will address questions about the plume structure and its dust size and velocity distribution. In this work, we investigate the plume evolution through modelling of the dust dynamics motion after the impact. We used a 3D+t non-spherical dust dynamical model, varying the sets of initial parameters. In particular, we use an assumed simple power law particle size-frequency distribution and three sets of other parameters obtained by three different approaches: 1) analytical scaling laws 2) the ejecta initial properties (ejecta mass, velocity, launch position distribution, orientation) constrained with iSALE numerical simulations and 3) SPH numerical simulations. Here, we focus mainly on the influence of the non-sphericity of the particles on the dynamical properties of the plume, such as velocity and dust spatial distribution. In addition, we provide information regarding the optical thickness not only in terms of particle size distribution but also as a function of particle shape and orientation. The main results regard the motion of non-spherical particles with different initial temperatures and angular velocities. By varying the initial angular velocity of the ejected particles, provided with the obtained dependence on the assumed particles' temperature, we can study what amount of dust particles' rotational energy after the thermal shock due to the impact is necessary to intrude the rapidly expanding plume. Alternatively, we can obtain what minimum initial threshold speed for a given type of dust (in terms of size, density and launch angle) is sufficient to govern the plume evolution independently from the intensity of the thermal shock and rotation state of the ejected dust particles.

Non-Spherical Dust Dynamics of the Ejecta Plume in Support of Dart/liciacube Mission

Bertini, I.;Palumbo, P.;
2021

Abstract

In the mid of 2021, NASA's Double Asteroid Redirection Test (DART) mission will be launched, starting its journey towards binary asteroid (65803) Didymos. In autumn 2022, DART (with a total mass of ~650 kg) will be the first space mission demonstrating the kinetic impactor technique for planetary defense by impacting Dimorphos, the 164±18 m-size secondary, with a speed of ~6.6 km/s. Such impact is expected to form a crater and a dense ejecta plume that will propagate rapidly in the near-by asteroid environment. While DART will be impacting Dimorphos, the Light Italian CubeSat for Imaging of Asteroids (LICIACube) (to be released from DART ten days before the impact) will both image the expanding plume and reveal the surface changes/processes that will occur after the impact. LICIACube will provide multiple images of the target down to a minimum distance of ~55 km from Dimorphos. The LICIACube narrow- and wide-angle cameras - LEIA (LICIACube Explorer Imaging for Asteroid) and LUKE (LICIACube Unit Key Explorer), respectively – will capture the post-impact processes and therefore describe the in-situ events, such as the newly formed crater, the expanding slow (<5 m/s) ejecta and the dynamics of its plume. In particular, LICIACube will address questions about the plume structure and its dust size and velocity distribution. In this work, we investigate the plume evolution through modelling of the dust dynamics motion after the impact. We used a 3D+t non-spherical dust dynamical model, varying the sets of initial parameters. In particular, we use an assumed simple power law particle size-frequency distribution and three sets of other parameters obtained by three different approaches: 1) analytical scaling laws 2) the ejecta initial properties (ejecta mass, velocity, launch position distribution, orientation) constrained with iSALE numerical simulations and 3) SPH numerical simulations. Here, we focus mainly on the influence of the non-sphericity of the particles on the dynamical properties of the plume, such as velocity and dust spatial distribution. In addition, we provide information regarding the optical thickness not only in terms of particle size distribution but also as a function of particle shape and orientation. The main results regard the motion of non-spherical particles with different initial temperatures and angular velocities. By varying the initial angular velocity of the ejected particles, provided with the obtained dependence on the assumed particles' temperature, we can study what amount of dust particles' rotational energy after the thermal shock due to the impact is necessary to intrude the rapidly expanding plume. Alternatively, we can obtain what minimum initial threshold speed for a given type of dust (in terms of size, density and launch angle) is sufficient to govern the plume evolution independently from the intensity of the thermal shock and rotation state of the ejected dust particles.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11367/106658
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