IAU Colloquium 165, Dynamics and Astrometry of Natural and Artificial Celestial Bodies, was held in Poznan, Poland, in July 1996, bringing together over 200 scientists from 27 countries who discussed their work in 179 oral and poster presentations. The present volume contains 83 of the papers presented at the meeting. The meeting brought together specialists from diverse fields who focused on the very close collaboration between dynamics and astrometry, where one discipline contributes to the progress of the other. The oral sessions were organized into general categories pertaining to: solar system dynamics; new observational techniques, catalogues, and astrometry; dynamics and observational problems of artificial satellites and space debris; rotation of solar system objects; reference systems and astronomical standards; new mathematical techniques; and three all-day poster sessions. This volume is divided into seven parts, comprising 83 contributions, a list of participants and an index.

"Fundamental Astronomy and Solar System Dynamics," a program of invited papers honoring Professor Walter Fricke, who for thirty years has been Director of the Astronomisches Rechen lnstitut in Heidelberg, was held at the Thompson Conference Center of the University of Texas at Austin on Wednesday 27 March 1985 on the occasion of his seventieth birthday and retirement as Director of ARl. Professor Fricke's contributions to astronomy encompass the areas of galactic dynamics, radial velocities, stellar statistics. the fundamental reference system and the constant of precession. Participants were welcomed to the Uni versi ty of Texas by Professor J. Parker Lamb, Chairman of the Department of Aerospace Engineering and Engineering Mechanics. The presentations ranged from discussions of astrometric problems concerned with the reference system, the constant of precession, major and minor planet observations, planetary ephemerides and lunar and satellite laser ranging, to a study of disc galaxies in massive halos. The program concluded with a review of Professor Fricke's career. The three sessions were chaired by Victor G. Szebehely, Carol A. Williams and Jay H. Lieske. The participants in this meeting, and in the Division on Dynamical Astronomy meeting that followed, were happy that Professor Fricke was able to attend. His presence at these meetings, as well as his thoughtful comments, were greatly appreciated. We are pleased to acknowledge the support of the Center for Space Research, the Department of Astronomy and the Department of Aerospace Engineering and Engineering Mechanics of the University of Texas at Austin.

IAU Colloquium 165, Dynamics and Astrometry of Natural and Artificial Celestial Bodies, was held in Poznan, Poland, in July 1996, bringing together over 200 scientists from 27 countries who discussed their work in 179 oral and poster presentations. The present volume contains 83 of the papers presented at the meeting. The meeting brought together specialists from diverse fields who focused on the very close collaboration between dynamics and astrometry, where one discipline contributes to the progress of the other. The oral sessions were organized into general categories pertaining to: solar system dynamics; new observational techniques, catalogues, and astrometry; dynamics and observational problems of artificial satellites and space debris; rotation of solar system objects; reference systems and astronomical standards; new mathematical techniques; and three all-day poster sessions. This volume is divided into seven parts, comprising 83 contributions, a list of participants and an index.

"Fundamental Astronomy and Solar System Dynamics", a program of invited papers honoring Professor Walter Fricke, who for thirty years has been Director of the Astronomisches Rechen lnstitut in Heidelberg, was held at the Thompson Conference Center of the University of Texas at Austin on Wednesday 27 March 1985 on the occasion of his seventieth birthday and retirement as Director of ARl. Professor Fricke's contributions to astronomy encompass the areas of galactic dynamics, radial velocities, stellar statistics. the fundamental reference system and the constant of precession. Participants were welcomed to the Uni versi ty of Texas by Professor J. Parker Lamb, Chairman of the Department of Aerospace Engineering and Engineering Mechanics. The presentations ranged from discussions of astrometric problems concerned with the reference system, the constant of precession, major and minor planet observations, planetary ephemerides and lunar and satellite laser ranging, to a study of disc galaxies in massive halos. The program concluded with a review of Professor Fricke's career. The three sessions were chaired by Victor G. Szebehely, Carol A. Williams and Jay H. Lieske. The participants in this meeting, and in the Division on Dynamical Astronomy meeting that followed, were happy that Professor Fricke was able to attend. His presence at these meetings, as well as his thoughtful comments, were greatly appreciated. We are pleased to acknowledge the support of the Center for Space Research, the Department of Astronomy and the Department of Aerospace Engineering and Engineering Mechanics of the University of Texas at Austin.

IA U Symposium Number 141 "Inertial Coordinate System on the Sky" was held in Leningrad, USSR from 17-21 October 1989. The symposium also commemorated the 150th anniversary of the founding of Pulkovo Observatory. The scientific program was presented in ten half-day sessions. Most sessions were held at the Pulkovskaya Hotel, but one session which highlighted Pulkovo's current programs was held at Pulkovo Observatory. The sessions were organized into general categories pertaining to the legacy of Pulkovo for inertial systems; current programs at Pulkovo Observatory; concepts, definitions and models; and the realization and comparision of reference frames. More than 140 scientific papers were presented, either orally or in poster form. Extensive use was made of electronic mail and computer-readable communications, and more than two-thirds of the authors made use of the opportunity to submit papers for formatting by the editors. The meeting was truly a symposium in the Greek sense of the word-a free-flowing exchange of ideas and opinions. The final two papers presented at the symposium by Wilkins and by Westerhout are presented at an eady stage in the published proceedings, in order to help focus the reader's attention on the concepts and problems explored in subsequent papers. As pointed out by G.