Temporary Capture of Asteroid Ejecta into Periodic Orbits

Abstract

In the framework of JAXA’s Hayabusa2 mission, we study the dynamical environment around asteroid Ryugu to investigate whether ejecta particles can be temporarily trapped in periodic orbits following the Small Carry-on Impactor (SCI) operation. If these particles remain about the asteroid, they could potentially jeopardize the mission as, in the event of a collision with the Hayabusa2 spacecraft, the spacecraft’s functionality could be reduced. In
this paper, we make use of invariant manifold theory to assess the conditions - impact location, particle radius, ejection velocity - that cause ejecta particles to get captured in periodic orbits. The analysis is carried out within the dynamical framework of the perturbed Augmented Hill Problem, which takes into account the solar radiation pressure, the effect of eclipses, and the J2 and J4 terms of the asteroid’s gravity potential in its spherical harmonics expansion. We analyze millimeter to centimeter sized particles and captures into three families of periodic orbits that are robust to large values of the solar radiation pressure acceleration – the traditional a and g’ families of the Hill Problem and the southern halo orbits. We go on to find the impact locations for the SCI from where ejecta particles are most likely to be captured into periodic orbits via their stable manifolds. As such, we recover the sets of initial states that lead ejecta to temporary orbital capture and show that solar radiation pressure cannot be neglected in these analyses, identifying locations on the Sun side of the asteroid at medium latitudes as the best impact locations.