Opportunities for Ballistic Soft Landing in Binary Asteroids

Abstract

Remote sensing instrumentation on-board missions to asteroids is paramount to address many of the fundamental questions in modern planetary science. Yet, in-situ surface measurements provide the "ground-truth" necessary to validate and enhance the science return of these missions. Nevertheless, due to the dynamical uncertainties associated with the environment near these objects, most missions spend long periods of times stationed afar. Small landers can be used much more daringly, however, and thus have already been identified as valuable assets for insitu exploration. This paper explores the potential for ballistic landing opportunities enabled by the natural dynamics found in binary asteroid systems. The dynamics near a binary asteroid are modelled by means of the Circular Restricted Three Body Problem, which provides a reasonable representation of a standard binary system. Natural landing trajectories are then sought that allow for a deployment from the exterior region and touchdown with minimum local-vertical velocity. The results show that while landing on the main body of the system would require an effective landing system capable to dissipate excess of energy, and avoid bouncing off the asteroid, the smaller companion offers the prospect of simple ballistic landing opportunities. Nomenclature a = Semi-major axis of the mutual binary asteroid orbit [km]

A comparative reliability analysis of ballistic deployments on binary asteroids

“…Along the same line of studies, Ferrari and Lavagna performed a trajectory design study and Monte Carlo simulations against uncertainties for MASCOT-2 [14]. In a more recent study, Ç elik and Sánchez proposed a new technique in CR3BP to search opportunities for ballistic soft landing in binary asteroids [15]. This technique defines a landing in local vertical and utilizes a bisection search algorithm to find minimum energy trajectories in backwards propagation from the surface.…”

“…Ç elik and Sánchez (2017) previously showed that landing trajectories onto larger companions of binaries (thereafter called as the primaries) entail higher energy landing trajectories, which; on the one hand may put the payload on the lander at risk due to the higher touchdown velocities, and on the other hand, do not guarantee that the lander will remain in the surface of the primary, unless very low coefficient of restitution can be ensured [15]. Hence, this paper focuses only on landing in the secondary, which was previously shown to potentially enable ballistic soft landing [15]. The paper particularly addresses the reliability aspects of the deployment operations under realistic uncertainties and errors in navigation and deployment systems.…”

“…A dense grid of first touchdown points is created and distributed homogeneously on the surface, whose locations are described by their latitudes and longitudes. Trajectories are then generated from each point in by applying the methodology developed in [15]. This allows us to obtain nominal trajectories under ideal conditions, as well as to generate a database of reachable regions and characteristics of landings on the surface as a function of landing location.…”

A New Mechanism for Soft Landing in Robotic Space Exploration

“…Two fields of study emerge which are of interest: that of the dynamics of landing and that of the interaction with the soil during impact. Since the 1960s, multi-legged landing systems are considered the state of the art [10] for low-velocity impact during powered descent, while ballistic landing systems have been proposed as well [11]. The reliability of landing systems is critical to the success of the mission [12], both structurally [13,14] as well as functionally [9].…”

“…Finally, the effect of the soil itself is generally nontrivial to model [17][18][19][20]; it can be simulated using numerical methods [17] or experimentally. The physics of impact and energy dissipation during collisions and landing have been studied from a structural point of view [21][22][23], from a dynamics perspective [1,2,10,16,[23][24][25], and as a mission-planning problem [11,26].…”