DPS 34th Meeting, October 2002
Session 27. Comet Nuclei
Oral, Chair(s): C. Lisse and Y.R. Fernandez, Thursday, October 10, 2002, 2:00-4:00pm, Ballroom

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[27.01] A Numerical Impact Ejecta Model for the Deep Impact Mission

J. E. Richardson, H. J. Melosh (Lunar and Planetary Laboratory, U. Arizona)

In July of 2005, the Deep Impact spacecraft will release a 370 kg impactor into the path of comet 9P/Tempel 1, and then move to a save distance to observe the resulting collision and it's effects. As part of the mission planning for this event, we have developed a numerical, Monte-Carlo simulation which models (via ``tracer particles") the ejecta plume, ejecta blanket, and impact crater area resulting from a specified impact on an irregularly shaped target body (modeled in 3-dimensional polygon fashion). The target body can be placed in a simple rotation state about one of its principal axes, with the impact site and projectile/target parameters selected by the user. The model is based upon the impact ejecta scaling laws developed by Housen, Schmidt, and Holsapple (1983), modified to more properly simulate late-stage ejection velocities and ejecta plume shape changes (ejection angle variations). Additionally, a target strength parameter has been added to allow the simulation of strength-dominated cratering events as well as the more familiar gravity-dominated cratering events.

This model has two primary uses:

(1) Coupled with an appropriate display module, it will be used in planning the instrument image sequences for the comet flyby spacecraft, allowing us to simulate the acquired images from a number of possible impact scenarios.

(2) It will provide a method for directly modeling the behavior of the actually observed ejecta plume, which will then be used to estimate the mass/density of Temple 1 based upon the effects of the comet's gravity field on crater formation and ejecta plume behavior. In addition, measurements of the observed ejecta plume size and expansion velocity as a function of time can be compared to a family of expected behavior curves produced by our numerical model, in order to improve this mass/density estimation.

If the author provided an email address or URL for general inquiries, it is as follows:

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.