GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    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
    BibTip Others were also interested in ...
    Online Resource
  • 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
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Double Asteroid Redirection Test (DART): Structural and Dynamic Interactions between Asteroidal Elements of Binary Asteroid (65803) Didymos
    American Astronomical Society ; 2022
    In:  The Planetary Science Journal Vol. 3, No. 6 ( 2022-06-01), p. 140-
    Details
    In: The Planetary Science Journal, American Astronomical Society, Vol. 3, No. 6 ( 2022-06-01), p. 140-
    Abstract: NASA's Double Asteroid Redirection Test (DART) mission is the first full-scale planetary defense mission. The target is the binary asteroid (65803) Didymos, in which the smaller component Dimorphos (∼164 m equivalent diameter) orbits the larger component Didymos (∼780 m equivalent diameter). The DART spacecraft will impact Dimorphos, changing the system’s mutual orbit by an amount that correlates with DART's kinetic deflection capability. The spacecraft collision with Dimorphos creates an impact crater, which reshapes the body. Also, some particles ejected from the DART impact site on Dimorphos eventually reach Didymos. Because Didymos’s rapid spin period (2.26 hr) may be close to its stability limit for structural failure, the ejecta reaching Didymos may induce surface disturbance on Didymos. While large uncertainties exist, nonnegligible reshaping scenarios on Didymos and Dimorphos are possible if certain conditions are met. Our analysis shows that given a surface slope uncertainty on Dimorphos of 45°, with no other information about its local topography, and if the DART-like impactor is treated as spherical, the ejecta cone crosses Didymos with speeds ≳14 m s −1 in 13% of simulations. Additional work is necessary to determine the amount of mass delivered to Didymos from the DART impact and whether the amount of kinetic energy delivered is sufficient to overcome cohesive forces in those cases. If nonnegligible (but small) reshaping occurs for either of these asteroids, the resulting orbit perturbation and reshaping are measurable by Earth-based observations.
    Type of Medium: Online Resource
    ISSN: 2632-3338
    URL: Article
    DOI: 10.3847/PSJ/ac6eff
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 3021068-9
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...