orbit stability about small near-earth asteroids

Paper number

IAC-09.A3.I.8

Author

Mr. Benjamin Vanoutryve, University of Liege, Belgium

Year

2009

Abstract

Small near-Earth asteroids (SNEA) are asteroids with a diameter typically under 1km and whose orbits bring them into close proximity with the Earth. The smallness of this family of asteroids gives them very irregular shapes. Those objects can be physically explored with low mission velocity due to their combination of low velocity with respect to Earth and very small gravity.

In addition, SNEA represent interesting targets for future space exploration missions. First, a spacecraft orbiting about such objects for extended periods would provide high-quality determinations and long term predictions of their trajectories. Furthermore, freely orbiting about irregularly shaped asteroids permit the precise characterisation and mitigation of their gravity fields, shapes, and masses, which are data of prime importance for potential deflecting mission. The latter could also use the spacecraft orbiting the target as a beacon for high-precision navigation. Finally, because asteroids are believed to have formed some billions years ago during the formation of our solar sytem, they represent attractive scientific opportunities for geochemical and astronomical investigation.

For a spacecraft orbiting about a small body, solar radiation pressure force is the main perturbation alongside the gravity field. Because of the very irregular shapes, the corresponding gravity fields are far from the approximation of a spherical mass used for bigger objects. An approximate method for computation of the gravity force is thus used: known as the “mascon” method, it considers the approach of building the body’s shape utilizing a collection of spherical masses of uniform density. The gravitational potential at the spacecraft can then be found by summing the contribution from each element. This paper assesses the accuracy of this approach by comparing it with the classical method using spherical harmonic expansion of a sphere.

Self-stabilizing orbits exist around small asteroids. Such orbits do not require stationkeeping maneuvers and make use of the main perturbing force, solar radiation pressure. This paper proposes to exhaustively seek for when the orbits are self-stabilizing or not, depending on the characteristics of both the asteroid and the spacecraft. A numerical model of the motion of a spacecraft in close proximity of a small object is implemented. Numerous simulations are then carried out in order to obtain a complete classification of self-stabilizing orbits.

Situations in which the orbits are stable are eventually discussed, yielding to a first fast evaluation of asteroid targets for further definition of missions to SNEA.

Abstract document

IAC-09.A3.I.8.pdf

Manuscript document

IAC-09.A3.I.8.pdf (🔒 authorized access only).

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