Libration-induced Orbit Period Variations Following the DART Impact

The Double Asteroid Redirection Test (DART) mission will be the first test of a kinetic impactor as a means of planetary defense. In late 2022, DART will collide with Dimorphos, the secondary in the Didymos binary asteroid system. The impact will cause a momentum transfer from the spacecraft to the binary asteroid, changing the orbit period of Dimorphos and forcing it to librate in its orbit. Owing to the coupled dynamics in binary asteroid systems, the orbit and libration state of Dimorphos are intertwined. Thus, as the secondary librates, it also experiences fluctuations in its orbit period. These variations in the orbit period are dependent on the magnitude of the impact perturbation, as well as the system’s state at impact and the moments of inertia of the secondary. In general, any binary asteroid system whose secondary is librating will have a nonconstant orbit period on account of the secondary’s fluctuating spin rate. The orbit period variations are typically driven by two modes: a long period and a short period, each with significant amplitudes on the order of tens of seconds to several minutes. The fluctuating orbit period offers both a challenge and an opportunity in the context of the DART mission. Orbit period oscillations will make determining the post-impact orbit period more difficult but can also provide information about the system’s libration state and the DART impact.

Forced Resonance Orbit Analysis of Binary Asteroid System

The solar radiation pressure becomes one of the major perturbations to orbits in the study of binary asteroid system, since asteroids have relatively weak gravity fields. In this paper, based on the idea of treating the solar radiation pressure as periodic external excitation, one novel family of orbits due to primary resonance and another novel family of orbits due to both primary resonance and internal resonance have been found by the classical perturbation method. The two types of steady-state orbits due to external resonance with different area-to-mass ratios have been determined and discussed by the frequency-response equations. Five binary asteroid systems, 283 Emma-S/2003 (283) 1, 22 Kalliope-Linus, 31 Euphrosyne-S/2019 (31) 1, 2006 Polonskaya-S/2005 (2006) 1 and 4029 Bridges have been taken as examples to show the validity of the proposed mechanism in the explanation of orbits formation due to resonance.

Juventas Cubesat for the Hera mision

<p>The Juventas CubeSat, will be delivered to the Didymos binary asteroid system by ESA's Hera mission within the context of the Asteroid Impact and Deflection Assessment (AIDA) international collaboration. AIDA is a technology demonstration of the kinetic impactor concept to deflect a small asteroid and to characterize its physical properties. Due to launch in 2024, Hera would travel to the binary asteroid system Didymos. It will explore the binary asteroid and the crater formed by the kinetic impact the NASA’s Double Asteroid Redirection Test (DART). HERA will carry two 6U CubeSats, one of which is the Juventas CubeSat developed by GomSpace Luxembourg with the Royal Observatory of Belgium as principal investigator. The spacecraft will attempt to characterize the internal structure of Didymos’ secondary body, Dimorphos, over a period of roughly 2 months using a low-frequency radar, JuRa. During this period, Juventas will also perform radio science measurements using its Inter-Satellite-Link to characterize the mass and mass distribution of Dimorphos. Afterwards, Juventas will attempt to land on Dimorphos, during which the spacecraft is expected to perform several bounces. Once landed, Juventas will use its gravimeter GRASS to obtain measurements of the surface acceleration on Dimorphos for a nominal duration of two orbits. Through the monitoring of dynamics for landing and bouncing impacts as well as measurements from the GRASS gravimeter payload while on the surface, Juventas will determine surface mechanical properties and provide further information on subsurface structure and dynamical properties of Dimorphos.</p>