2015.A.2.1. CubeSat Landing Opportunities for Binary Asteroid Exploration

Author(s)

Onur Celik (1)
Joan Pau Sanchez (1)

Cranfield University, United Kingdom

Session

A.2

Keywords

CubeSat, Binary Asteroids, CR3BP, Landing

Abstract

Missions to asteroids have become increasingly attractive in recent years, firstly, due to their scientific value, but also because of their potential risk to Earth and prospective economic return. A variety of missions have been proposed, ranging from manned exploration to commercial mining missions. There have already been missions to asteroids (e.g. Hayabusa) which brought samples and scientific data, while successor spacecraft are on their way to new targets. For such and future missions, it is essential to perform in-situ observations by landers in order to enhance scientific return. Simple, reliable and low-cost lander modules would satisfy the desired observational capability by exploiting the natural dynamics of these bodies. Therefore, CubeSat systems are good candidates to fulfil the aforementioned exploration demands. This paper considers a mission architecture that includes a mothership carrying one or several CubeSats. The mission is targeted to a binary asteroid system, which constitute about 15% of the population of near Earth asteroids. The binarysystem is assumed to have a secondary object with a radius of 0.35Rprimary, orbiting a primary on a circular orbit with orbital radius of 3.25Rprimary. The mothership operational orbit is such that the possibility of a collision with the asteroid is ruled out. This is thus equivalent to have zero-velocity curves of the system closed at the L2 point, while the mothership would orbit in the exterior region. The CubeSat deployment is performed by means of a spring mechanism, which provides sufficient velocity to the CubeSat to open up the zero-velocity curves near the L2 point. Hence, the CubeSat can then land ballistically into the asteroid system. Standardized CubeSat deployer is considered to limit the deployment velocity to maximum 2 m/s. The landing must be such that the final touchdown velocity is in local vertical direction, and its magnitude sufficiently small to prevent damage to the CubeSat. After defining touchdown velocities and positions, the ballistic landing is propagated backwards in time, from the surface until it transits through the bottleneck region of L2 point. The Circular Restricted Three Body Problem framework is used, which implies that no perturbations other than the point mass gravity of the primary and secondary asteroids in the binary system are considered. The results are then used for preliminary subsystem design for CubeSat, to ensure the proposed landing. The paper provides new insights into the regions and sizes of binary systems that could potentially be explored by simple underactuated systems with little control.