This volume contains the detailed text of the major lectures and the abstracts of the lectures delivered during the seminar sessions. The subject of our NATO Advanced Study Institute in 1981 was the Application of Modern Dynamics to Celestial Mechanics and Astrodynamics. This Preface will first explain the terminology, then it will review shortly the content of the lectures and will outline how all this was made possible and, finally, it will disclose our future aspirations. Periodicity is an extremely important concept in our field, therefore, it should not be unexpected that our NATO Advanced Study Institute is enjoying a period of three years. Since 1972 we conducted four Institutes with increasing interest and en thusiasm displayed by the participants, lecturers and by this Director. Celestial Mechanics or Dynamical Astronomy is part of Astronomy dealing mostly with the motion of natural celestial bodies. Astrodynamics or Orbital Mechanics is the application of dynamics to problems of Space Engineering and it treats mostly the dynamical behavior of artificial satellites and space probes. The underlying mathematical and dynamical principles are, of course, the same for Celestial Mechanics and for Astrodynamics. This Director of the Institute and Editor of the Proceedings was extremely fortunate to have obtained the cooperation of out standing lecturers who were clear, thorough, understandable, patient to answer questions, but above all, had knowledge of the ix V. Szebehely (ed.). Applications of Modern Dynamics to Celestial Mechanics and Astrodynamics. ix-x."

This volume contains lectures given at the NATO Advanced Study Institute on Long-Time Predictions in Dynamics conducted in Cortina d'Ampezzo, Italy during August 3-16, 1975. The lectures were presented in groups, according to the original structure of the Institute. Under "Fundamentals" the general concepts were treated by Contopoulos, DeWitt, Reichl, Stiefel, Szebehely, Bartlett, Kirchgraber, Verhults and Sigrist. This was followed by the series of lectures on "Numerical and Statistical Analysis" offered by Aarseth, Baumgarte and Tapley. The third principal subject was "Three and Many-Body Problems" with Garfinkel, Broucke, Hadjidemetriou, Marchal, Nahon, Waldvogel, Lasco, and Markellos as the major speakers. The last group of lectures treated "Dynamics in Astronomy" by Colombo, Message, Ovenden, Vicente, and Douglas. Some of the outstanding lectures were rather didactic in nature or were published elsewhere or could not meet the deadline for publication. The Editors will be delighted to furnish leads to those interested in these lectures. Some of the lectures were presented in form of seminar-contributions. These are published as Summaries at the end of this Volume. The Institute was dedicated to the conceptual, analytical, numerical and applied aspects of the problem of long-time predic tion in dynamics. This fundamental problem emerged in all lectures: linearization, regularization, stabilization, averaging, estimation, periodic orbits, qualitative aspects, secular variations, resonance, invariants, etc. were some of the subjects treated in depth. Some conclusions are offered here with the utmost humility and with the advance acknowledgement of the fact that we all hear what we want to hear."

It is this editor's distinct pleasure to offer to the readership the text of the lectures presented at our recent NATO Advanced Study Institute held in Cortina d'Ampezzo, Italy between August 6 and August 17, 1984. The invited lectures are printed in their entirety while the seminar contributions are presented as abstracts. Our Advanced Study Institutes were originated in 1972 and the reader, familiar with periodic phenomena, so important in Celestial Mechanics, will easily establish the fact that this Institute was our fifth one in the series. We dedicated the Institute to the subject of stability which itself is a humbling experience since it encompasses all fields of sciences and it is a basic element of human culture. The many definitions in existence and their practical applications could easily fill another volume. It is known in this field that it is easy to deliver lectures or write papers on stability as long as the definition of stability is carefully avoided. On the other hand, if one selects a definition, he might be criticized for using that definition and not another one. In this volume we carefully defined the specific concept of stability used in every lecture. If the reader wishes to introduce other definitions we feel that he should be entirely free and we encourage him to do so. It is also known that certain sta bility definitions and concepts are more applicable to certain given fields than to others."

IX LIST OF PRINCIPAL SPEAKERS XI LIST OF PARTICIPANTS 1. REGULARIZATION E. STIEFEL / A Linear Theory of the Perturbed Two-Body Problem (Regul- ization) 3 J. WALDVOGEL / Collision Singularities in Gravitational Problems 21 D. C. HEGGIE / Regularization Using a Time-Transformation Only 34 J. BAUMGAR TE / Stabilization of the Differential Equations of Keplerian Motion 38 F. NAHON / The Particular Solutions of Levi-Civita 45 O. GODAR T / Example ofIntegration of Strongly Oscillating Systems 53 w. BLACK / The Application of Recurrence Relations to Special Perturbation Methods 61 D. G. BETTIS / Numerical Solution of Ordinary Differential Equations (Abstract) 71 II. THE THREE-BODY PROBLEM V. SZEBEHELY / Recent Advances in the Problem of Three Bodies 75 R. F. ARENSTORF / Periodic Elliptic Motion in the Problem of Three Bodies (Abstract) 107 G. KATSIARIS and c. L. GOUDAS / On a Conjecture by Poincare 109 G. KATSIARIS / The Three-Dimensional Elliptic Problem 118 P. G. KAZANTZIS / Second and Third Order Variations of the Three Dimensional Restricted Problem 135 c. G. ZAGOURAS / Planar Periodic Orbits Using Second and Third Variations 146 E. RABE / Elliptic Restricted Problem: Fourth-Order Stability Analysis of the Triangular Points 156 P. GUILLAUME / A Linear Description of the Second Species Solutions 161 III. THE N-BODY PROBLEM AND STELLAR DYNAMICS G. CONTOPOULOS / Problems of Stellar Dynamics 177 w. T. KYNER / Invariant Manifolds in Celestial Mechanics 192 s. J.

ix List of Speakers and Participants xi Group Photograph xviii Greetings by B. Garfinkel, A. E. Roy and P. J. Message xix Introduction xxiii PART I: FUNDAMENTAL CONSIDERATIONS OF STABILITY R. BROUCKE/Simple Non-Integrable Systems with Two Degrees of Freedom 3 G. CONTOPOULOS/lnstabilities in Systems of Three Degrees of Freedom 25 R. W. EASTON/Perturbed Twist Maps, Homoclinic Points and Ergodic Zones 41 O. GUREL/Bifurcation Theory and its Applications V. SZEBEHELY/General Considerations of Stability in 49 61 Celestial Mechanics PART II: ASPECTS OF NUMERICAL ANALYSIS AND STATISTICAL MECHANICS S. J. AARSETH/An N-Body Integration Method in Co-Moving Coordinates 69 J. BAUMGARTE/The General Theory of Conservative Stabilization of the Keplerian Problem 81 C. DEWITT-MORETTE /Celestial Mechanics, Quantum Mechanics, and Path Integration 95 G. C. STEY/Statistical Viewpoint in Classical Mechanics 103 PART III: STABILITY OF PLANETARY SYSTEMS ~ C. FROESCHLE and H. SCHOLL/Evolution of Orbits in the Outer Part of the Asteroidal Belt and in the Kirkwood Gaps as Influenced by the Mass Effects of Saturn and Jupiter 115 v TABLE OF CONTENTS vi B. GARFINKEL/On the Stability of Resonant Motion in 121 the Light of the Regularizing Function 129 P. GOLDREICH/The Rings of Saturn and Uranus J. D. HADJIDEMETRIOU/Instabilities in Periodic 135 Planetary-Type Orbits P. J. MESSAGE/Bounds on Secular Terms in Celestial 165 Mechanics A. E. ROY/Empirical Stability Criteria in the 177 Many-Body Problem R. O. VICENTE/Instabilities in Planetary Systems 211 PART IV: THE PROBLEM OF THREE BODIES H.

This volume contains the detailed text of the major lectures and the abstracts of the lectures delivered during the seminar sessions. The subject of our NATO Advanced Study Institute in 1981 was the Application of Modern Dynamics to Celestial Mechanics and Astrodynamics. This Preface will first explain the terminology, then it will review shortly the content of the lectures and will outline how all this was made possible and, finally, it will disclose our future aspirations. Periodicity is an extremely important concept in our field, therefore, it should not be unexpected that our NATO Advanced Study Institute is enjoying a period of three years. Since 1972 we conducted four Institutes with increasing interest and en thusiasm displayed by the participants, lecturers and by this Director. Celestial Mechanics or Dynamical Astronomy is part of Astronomy dealing mostly with the motion of natural celestial bodies. Astrodynamics or Orbital Mechanics is the application of dynamics to problems of Space Engineering and it treats mostly the dynamical behavior of artificial satellites and space probes. The underlying mathematical and dynamical principles are, of course, the same for Celestial Mechanics and for Astrodynamics. This Director of the Institute and Editor of the Proceedings was extremely fortunate to have obtained the cooperation of out standing lecturers who were clear, thorough, understandable, patient to answer questions, but above all, had knowledge of the ix V. Szebehely (ed.). Applications of Modern Dynamics to Celestial Mechanics and Astrodynamics. ix-x."

It is this editor's distinct pleasure to offer to the readership the text of the lectures presented at our recent NATO Advanced Study Institute held in Cortina d'Ampezzo, Italy between August 6 and August 17, 1984. The invited lectures are printed in their entirety while the seminar contributions are presented as abstracts. Our Advanced Study Institutes were originated in 1972 and the reader, familiar with periodic phenomena, so important in Celestial Mechanics, will easily establish the fact that this Institute was our fifth one in the series. We dedicated the Institute to the subject of stability which itself is a humbling experience since it encompasses all fields of sciences and it is a basic element of human culture. The many definitions in existence and their practical applications could easily fill another volume. It is known in this field that it is easy to deliver lectures or write papers on stability as long as the definition of stability is carefully avoided. On the other hand, if one selects a definition, he might be criticized for using that definition and not another one. In this volume we carefully defined the specific concept of stability used in every lecture. If the reader wishes to introduce other definitions we feel that he should be entirely free and we encourage him to do so. It is also known that certain sta bility definitions and concepts are more applicable to certain given fields than to others."

P. J. MESSAGE University of Liverpool The papers which comprise this volume were presented at Colloquium No. 41 of the International Astronimical Union, which was held in Cambridge, England, from the 17th to the 19th of August, 1976, and had as its subject 'Dynamics of Planets and Satellites and Theories of their Motion'. The Colloquium was held just prior to the XVIth General Assembly of the Union (which was held from 24th August to 2nd September, in Grenoble, France) to provide an opportunity for the presentation of research papers on a number of active and lively branches of Celestial Mechanics to a gathering of experts in the field, and for the stimulus of discussion of research problems of interest to participants. A number of papers testify to the progress being made in General Planetary Theory, the theories of motion of the minor planets, the Moon, and the satellites of Jupiter and Saturn, and to significant advances in both the general and restricted gravitational problems of three bodies. The Organizing Committee of the Colloquium was comprised of J. Chapront, R. L. Duncombe, J. Hadjidemetriou, Y. Kozai, B. Morando, J. Schubart, V. Szebehely, and P. J. Message (Chairman). The local Organizer was D. C. Heggie, to whose tireless efforts the success of the arrangements is due. IX LIST OF PARTICIPANTS N. Abu-el-Ata, Bureau des Longitudes, 77 Avenue Denfert Rochereau, 75014 Paris, France K. Aksnes, Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, U. S. A.

This volume contains lectures given at the NATO Advanced Study Institute on Long-Time Predictions in Dynamics conducted in Cortina d'Ampezzo, Italy during August 3-16, 1975. The lectures were presented in groups, according to the original structure of the Institute. Under "Fundamentals" the general concepts were treated by Contopoulos, DeWitt, Reichl, Stiefel, Szebehely, Bartlett, Kirchgraber, Verhults and Sigrist. This was followed by the series of lectures on "Numerical and Statistical Analysis" offered by Aarseth, Baumgarte and Tapley. The third principal subject was "Three and Many-Body Problems" with Garfinkel, Broucke, Hadjidemetriou, Marchal, Nahon, Waldvogel, Lasco, and Markellos as the major speakers. The last group of lectures treated "Dynamics in Astronomy" by Colombo, Message, Ovenden, Vicente, and Douglas. Some of the outstanding lectures were rather didactic in nature or were published elsewhere or could not meet the deadline for publication. The Editors will be delighted to furnish leads to those interested in these lectures. Some of the lectures were presented in form of seminar-contributions. These are published as Summaries at the end of this Volume. The Institute was dedicated to the conceptual, analytical, numerical and applied aspects of the problem of long-time predic tion in dynamics. This fundamental problem emerged in all lectures: linearization, regularization, stabilization, averaging, estimation, periodic orbits, qualitative aspects, secular variations, resonance, invariants, etc. were some of the subjects treated in depth. Some conclusions are offered here with the utmost humility and with the advance acknowledgement of the fact that we all hear what we want to hear."

IX LIST OF PRINCIPAL SPEAKERS XI LIST OF PARTICIPANTS 1. REGULARIZATION E. STIEFEL / A Linear Theory of the Perturbed Two-Body Problem (Regul- ization) 3 J. WALDVOGEL / Collision Singularities in Gravitational Problems 21 D. C. HEGGIE / Regularization Using a Time-Transformation Only 34 J. BAUMGAR TE / Stabilization of the Differential Equations of Keplerian Motion 38 F. NAHON / The Particular Solutions of Levi-Civita 45 O. GODAR T / Example ofIntegration of Strongly Oscillating Systems 53 w. BLACK / The Application of Recurrence Relations to Special Perturbation Methods 61 D. G. BETTIS / Numerical Solution of Ordinary Differential Equations (Abstract) 71 II. THE THREE-BODY PROBLEM V. SZEBEHELY / Recent Advances in the Problem of Three Bodies 75 R. F. ARENSTORF / Periodic Elliptic Motion in the Problem of Three Bodies (Abstract) 107 G. KATSIARIS and c. L. GOUDAS / On a Conjecture by Poincare 109 G. KATSIARIS / The Three-Dimensional Elliptic Problem 118 P. G. KAZANTZIS / Second and Third Order Variations of the Three Dimensional Restricted Problem 135 c. G. ZAGOURAS / Planar Periodic Orbits Using Second and Third Variations 146 E. RABE / Elliptic Restricted Problem: Fourth-Order Stability Analysis of the Triangular Points 156 P. GUILLAUME / A Linear Description of the Second Species Solutions 161 III. THE N-BODY PROBLEM AND STELLAR DYNAMICS G. CONTOPOULOS / Problems of Stellar Dynamics 177 w. T. KYNER / Invariant Manifolds in Celestial Mechanics 192 s. J.