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  • 1
    Online Resource
    Online Resource
    Predictions for the Dynamical States of the Didymos System before and after the Planned DART Impact
    American Astronomical Society ; 2022
    In:  The Planetary Science Journal Vol. 3, No. 7 ( 2022-07-01), p. 157-
    Details
    In: The Planetary Science Journal, American Astronomical Society, Vol. 3, No. 7 ( 2022-07-01), p. 157-
    Abstract: NASA’s Double Asteroid Redirection Test (DART) spacecraft is planned to impact the natural satellite of (65803) Didymos, Dimorphos, at around 23:14 UTC on 2022 September 26, causing a reduction in its orbital period that will be measurable with ground-based observations. This test of kinetic impactor technology will provide the first estimate of the momentum transfer enhancement factor β at a realistic scale, wherein the ejecta from the impact provide an additional deflection to the target. Earth-based observations, the LICIACube spacecraft (to be detached from DART prior to impact), and ESA’s follow-up Hera mission, to launch in 2024, will provide additional characterizations of the deflection test. Together, Hera and DART comprise the Asteroid Impact and Deflection Assessment cooperation between NASA and ESA. Here, the predicted dynamical states of the binary system upon arrival and after impact are presented. The assumed dynamically relaxed state of the system will be excited by the impact, leading to an increase in eccentricity and a slight tilt of the orbit, together with enhanced libration of Dimorphos, with the amplitude dependent on the currently poorly known target shape. Free rotation around the moon’s long axis may also be triggered, and the orbital period will experience variations from seconds to minutes over timescales of days to months. Shape change of either body, due to cratering or mass wasting triggered by crater formation and ejecta, may affect β , but can be constrained through additional measurements. Both BYORP and gravity tides may cause measurable orbital changes on the timescale of Hera’s rendezvous.
    Type of Medium: Online Resource
    ISSN: 2632-3338
    URL: Article
    DOI: 10.3847/PSJ/ac76c9
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 3021068-9
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Pre-encounter Predictions of DART Impact Ejecta Behavior and Observability
    American Astronomical Society ; 2022
    In:  The Planetary Science Journal Vol. 3, No. 9 ( 2022-09-01), p. 206-
    Details
    In: The Planetary Science Journal, American Astronomical Society, Vol. 3, No. 9 ( 2022-09-01), p. 206-
    Abstract: We overview various efforts within the DART Investigation Team’s Ejecta Working Group to predict the characteristics, quantity, dynamical behavior, and observability of DART impact ejecta. We discuss various methodologies for simulation of the impact/cratering process with their advantages and drawbacks in relation to initializing ejecta for subsequent dynamical propagation through and away from the Didymos system. We discuss the most relevant forces acting on ejecta once decoupled from Dimorphos’s surface and highlight various software packages we have developed and used to dynamically simulate ejecta under the action of those forces. With some additional software packages, we explore the influence of additional perturbing effects, such as interparticle collisions within true N -body codes and nonspherical and rotating particles’ interplay with solar radiation pressure. We find that early-timescale and close-proximity ejecta evolution is highly sensitive to some of these effects (e.g., collisions) while relatively insensitive to other factors. We present a methodology for turning the time-evolving size- and spatially discretized number density field output from ejecta simulations into synthetic images for multiple platforms/cameras over wide-ranging vantage points and timescales. We present such simulated images and apply preliminary analyses to them for nominal and off-nominal cases bracketing realistic total mass of ejecta and ejecta cumulative size–frequency distribution slope. Our analyses foreshadow the information content we may be able to extract from the actual images taken during and after the DART encounter by both LICIACube and Earth-vicinity telescopes.
    Type of Medium: Online Resource
    ISSN: 2632-3338
    URL: Article
    DOI: 10.3847/PSJ/ac7fa1
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 3021068-9
    Location Call Number Limitation Availability
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  • 3
    Online Resource
    Online Resource
    After DART: Using the First Full-scale Test of a Kinetic Impactor to Inform a Future Planetary Defense Mission
    American Astronomical Society ; 2022
    In:  The Planetary Science Journal Vol. 3, No. 10 ( 2022-10-01), p. 244-
    Details
    In: The Planetary Science Journal, American Astronomical Society, Vol. 3, No. 10 ( 2022-10-01), p. 244-
    Abstract: NASA’s Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ∼10% and characterization of the Didymos binary system. But DART is a single experiment; how could these results be used in a future planetary defense necessity involving a different asteroid? We examine what aspects of Dimorphos’s response to kinetic impact will be constrained by DART results; how these constraints will help refine knowledge of the physical properties of asteroidal materials and predictive power of impact simulations; what information about a potential Earth impactor could be acquired before a deflection effort; and how design of a deflection mission should be informed by this understanding. We generalize the momentum enhancement factor β , showing that a particular direction-specific β will be directly determined by the DART results, and that a related direction-specific β is a figure of merit for a kinetic impact mission. The DART β determination constrains the ejecta momentum vector, which, with hydrodynamic simulations, constrains the physical properties of Dimorphos’s near-surface. In a hypothetical planetary defense exigency, extrapolating these constraints to a newly discovered asteroid will require Earth-based observations and benefit from in situ reconnaissance. We show representative predictions for momentum transfer based on different levels of reconnaissance and discuss strategic targeting to optimize the deflection and reduce the risk of a counterproductive deflection in the wrong direction.
    Type of Medium: Online Resource
    ISSN: 2632-3338
    URL: Article
    DOI: 10.3847/PSJ/ac94c1
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 3021068-9
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Effects of Impact and Target Parameters on the Results of a Kinetic Impactor: Predictions for the Double Asteroid Redirection Test (DART) Mission
    American Astronomical Society ; 2022
    In:  The Planetary Science Journal Vol. 3, No. 11 ( 2022-11-01), p. 248-
    Details
    In: The Planetary Science Journal, American Astronomical Society, Vol. 3, No. 11 ( 2022-11-01), p. 248-
    Abstract: The Double Asteroid Redirection Test (DART) spacecraft will impact into the asteroid Dimorphos on 2022 September 26 as a test of the kinetic impactor technique for planetary defense. The efficiency of the deflection following a kinetic impactor can be represented using the momentum enhancement factor, β , which is dependent on factors such as impact geometry and the specific target material properties. Currently, very little is known about Dimorphos and its material properties, which introduces uncertainty in the results of the deflection efficiency observables, including crater formation, ejecta distribution, and β . The DART Impact Modeling Working Group (IWG) is responsible for using impact simulations to better understand the results of the DART impact. Pre-impact simulation studies also provide considerable insight into how different properties and impact scenarios affect momentum enhancement following a kinetic impact. This insight provides a basis for predicting the effects of the DART impact and the first understanding of how to interpret results following the encounter. Following the DART impact, the knowledge gained from these studies will inform the initial simulations that will recreate the impact conditions, including providing estimates for potential material properties of Dimorphos and β resulting from DART’s impact. This paper summarizes, at a high level, what has been learned from the IWG simulations and experiments in preparation for the DART impact. While unknown, estimates for reasonable potential material properties of Dimorphos provide predictions for β of 1–5, depending on end-member cases in the strength regime.
    Type of Medium: Online Resource
    ISSN: 2632-3338
    URL: Article
    DOI: 10.3847/PSJ/ac91cc
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 3021068-9
    Location Call Number Limitation Availability
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