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The main topics of this proceedings stress the interactions between the theory of functional equations and the theory of dynamical systems. A total of 38 invited lectures are included.

Equadiff-91 stems from the series of conferences initiated by the late Professor Vogel. The first conference Equadiff-70 which was held in Marseille. Since then, similar conferences had been held in Brussels, Florence, Wurzburg as well as Xanthi. The purpose of the Equadiff series of conferences is to present the latest development in the field of differential equations, both ordinary and partial, including their numerical treatment and applications to the mathematics community. These conferences had attracted renowned mathematicians from all over the world to present their studies and findings. The latest conference under the series was Equadiff-91, held in Barcelona. It attracted some 30 renowned mathematicians. Researchers and graduate students of pure and applied mathematics will find this compilation of conference proceedings up-to-date, relevant and insightful.

The aim of this book is to explain, analyze and compute the kinds of motions that appear in an extended vicinity of the geometrically defined equilateral points of the Earth–Moon system, as a source of possible nominal orbits for future space missions. The methodology developed here is not specific to astrodynamics problems. The techniques are developed in such a way that they can be used to study problems that can be modeled by dynamical systems.

This book studies several problems related to the analysis of planned or possible spacecraft missions. It is divided into four chapters. The first chapter is devoted to the computation of quasiperiodic solutions for the motion of a spacecraft near the equilateral points of the Earth–Moon system. The second chapter gives a complete description of the orbits near the collinear point, L1, between the Earth and the Sun in the restricted three-body problem (RTBP) model. In the third chapter, methods are developed to compute the nominal orbit and to design and test the control strategy for the quasiperiodic halo orbits. In the last chapter, the transfer from the Earth to a halo orbit is studied.

It is well known that the restricted three-body problem has triangular equilibrium points. These points are linearly stable for values of the mass parameter, μ, below Routh's critical value, μ1. It is also known that in the spatial case they are nonlinearly stable, not for all the initial conditions in a neighborhood of the equilibrium points L4, L5 but for a set of relatively large measures. This follows from the celebrated Kolmogorov–Arnold–Moser theorem. In fact there are neighborhoods of computable size for which one obtains “practical stability” in the sense that the massless particle remains close to the equilibrium point for a big time interval (some millions of years, for example).According to the literature, what has been done in the problem follows two approaches: (a) numerical simulations of more or less accurate models of the real solar system; (b) study of periodic or quasi-periodic orbits of some much simpler problem.The concrete questions that are studied in this volume are: (a) Is there some orbit of the real solar system which looks like the periodic orbits of the second approach? (That is, are there orbits performing revolutions around L4 covering eventually a thick strip? Furthermore, it would be good if those orbits turn out to be quasi-periodic. However, there is no guarantee that such orbits exist or will be quasi-periodic). (b) If the orbit of (a) exists and two particles (spacecraft) are put close to it, how do the mutual distance and orientation change with time?As a final conclusion of the work, there is evidence that orbits moving in a somewhat big annulus around L4 and L5 exist, that these orbits have small components out of the plane of the Earth–Moon system, and that they are at most mildly unstable.

In this book the problem of station keeping is studied for orbits near libration points in the solar system. The main focus is on orbits near halo ones in the (Earth+Moon)–Sun system. Taking as starting point the restricted three-body problem, the motion in the full solar system is considered as a perturbation of this simplified model. All the study is done with enough generality to allow easy application to other primary-secondary systems as a simple extension of the analytical and numerical computations.