A dynamical definition of the sphere of influence of the Earth

TL;DR

This paper introduces a new dynamical definition of Earth's sphere of influence based on orbit optimization, accounting for position and velocity, improving impact monitoring and spacecraft trajectory design.

Contribution

It proposes a novel, optimization-based definition of the sphere of influence that depends on the small body's position and velocity, extending classical concepts.

Findings

New definition depends on position, velocity, and Jacobi constant

Comparison of three-body and two-body orbit models

Database of influence radii for various initial conditions

Abstract

The concept of sphere of influence of a planet is useful in both the context of impact monitoring of asteroids with the Earth and of the design of interplanetary trajectories for spacecrafts. After reviewing the classical results, we propose a new definition for this sphere that depends on the position and velocity of the small body for given values of the Jacobi constant $C$. Here we compare the orbit of the small body obtained in the framework of the circular restricted three-body problem, with orbits obtained by patching two-body solutions. Our definition is based on an optimisation process, minimizing a suitable target function with respect to the assumed radius of the sphere of influence. For different values of $C$ we represent the results in the planar case: we show the values of the selected radius as a function of two angles characterising the orbit. In this case, we also produce a database of radii of the sphere of influence for several initial conditions, allowing an interpolation.