Aerospace Engineering Seminar Series: Harrison Agrusa, Ph.D. Candidate in Astronomy, UMD
Wednesday, March 2, 2022
4:00 p.m.-5:00 p.m.
Virtual Hybrid/2164 Martin Hall, DeWalt Seminar Room
Modeling the spin and orbital dynamics of the Didymos binary asteroid, the target of NASA's DART Mission
Harrison Agrusa is a final-year Ph.D. Candidate in the Astronomy Department at the University of Maryland. His primary research interest lies in the spin and orbital dynamics of binary asteroids. However, he also has interests in scientific computing, high-velocity impacts, and planetary defense. Harrison grew up in Boise, Idaho and completed his undergraduate work at the University of California, Berkeley.
NASA's Double Asteroid Redirection Test (DART) Mission will be the first to demonstrate the kinetic impactor technique as a viable means to deflect a hazardous asteroid at a realistic scale. In September of this year, the DART spacecraft will collide with Dimorphos, the secondary component of the Didymos binary asteroid system at ~6.5 km/s. The kinetic impact will reduce Dimorphos' orbital velocity, leading to a reduction in the mutual semimajor axis and orbital period. Using Earth-based observations of the change in orbit period, an estimate of the momentum enhancement factor, or 'beta (β), can be obtained. β is an important parameter in planetary defense that describes the additional momentum enhancement that results from escaping material produced by the impact.
Due to the close proximity and non-spherical shapes of the two component asteroids, their spin and orbital dynamics are highly coupled and non-Keplerian. Therefore, the use of dedicated Full-Two Body Problem (F2BP) simulation codes are needed to robustly model the pre- and post-impact dynamics of the Didymos binary. Existing radar and photometric observations have placed strong constraints on the current system's orbital period and semimajor axis, as well as Didymos' shape and spin state. However, the current shape and spin of the secondary component, Dimorphos, is still unknown and poorly constrained. The DART impact will excite the libration state of Dimorphos, and depending on its shape, could lead to an attitude instability and chaotic rotation. This talk will summarize our current efforts at modeling the pre-impact state of the Didymos system, as well as our predictions for the highly-excited dynamics that will result from the DART impact.