In July 1995 the XXI General Assembly of the International Union of Geodesy and Geophysics was held in Boulder, Colorado. At this meeting the International Association of Geodesy (lAG) organized a number of symposia to discuss scientific developments and future directions in a number of areas. One of these symposia was G3, Global Gravity Field and Its Temporal Variations. This symposium consisted of four invited and 36 contributed papers. The contributed papers were given as oral or poster presentations. This proceedings volume represents the written contributions of the four invited papers (appearing as the first four papers in the volume) and 19 additional papers. The authors were asked to limit the length of their paper to approximately ten pages, which, in some cases, did limit what an author wanted to say. The papers in this volume have been placed in the same order as they were presented at the ruGG meeting. A key theme of the symposium is given in the paper by Nerem, Klosko, and Pavlis where they discuss applications of gravity field information in geodesy and oceanography. The significant achievements in determining the gravity field in the ocean areas from satellite altimeter data is discussed by Sandwell, Yale, McAdoo, and Smith. A review of time changes of the Earth's gravity field from terrestrial measurements is given by Lambert et aI. , and from satellite perturbation techniques by Eanes and Bettadpur. A description of new geopotential models is given in the paper by Tapley et al.

This book contains most of the papers presented at the G3 Symposium (Global and Gravity Field and Its Temporal Variations) sponsored by the International Association of Geodesy at the XXI General Assembly of the IUGG held in July 1995, Boulder, Colorado, USA. Four papers review the following areas: applications of global gravity models in geodesy and oceanography, high resolution gravity information in the oceans from satellite altimeter data, and temporal variations of the gravity field measured by terrestrial and satellite techniques. Other papers provide new results and future plans, for example, in the areas: global potental coefficient models, new terrestrial and altimeter-derived anomaly data, improved estimations Techniques, and use of GPS data in gravity field modeling.

In 1995, the German Space Agency DARA selected the CHAllenging Minisatellite Payload (CHAMP) mission for development under a special support programme for the space industry in the new states of the unified Germany, with the Principal Investigator and his home institution GFZ Potsdam being ultimately responsible for the success of all mission phases. After three years of spacecraft manufactur ing and testing, the satellite was injected successfully into its final, near circular, almost polar and low altitude (450 km) orbit from the cosmodrome Plesetsk in Russia on July 15, 2000. After a nine month commissioning period during which all spacecraft systems and instruments were checked, calibrated and validated, the satellite has been delivering an almost uninterrupted flow of science data since May 2001. Since this date, all science data have been made available to the more than 150 selected co-investigator teams around the globe through an international Announcement of Opportunity. The scientific goals of the CHAMP mission are to gain a better understanding of dynamic processes taking place in the Earth's interior and in the space near Earth. These goals can be achieved by improved observation of the Earth's gravity and magnetic fields and their time variability with high-performance on-board instru mentation and by exploring the structure of the Earth's atmosphere and ionosphere through radio occultation measurements.

Based on the IAG scientific assembly in Rio de Janeiro, Brazil, this volume combines papers in the fields of gravity and geoid, geodynamics, and geodesy in Antarctica. The volume contains papers on recent progress in absolute and relative gravimetry, on models of the global gravity field, theoretical developments in physical geodesy, and many examples of regional gravity field and geoid models. Geodynamics chapters include papers on earth rotation and geopotential variations, reference frames and global deformations, as well as a section on the combination of space and terrestrial methods for deformation observations. The current status of geodesy in Antarctica is illustrated by a number of papers.

Observational and experimental data pertaining to gravity and cosmology are changing our view of the Universe. General relativity is a fundamental key for the understanding of these observations and its theory is undergoing a continuing enhancement of its intersection with observational and experimental data. These data include direct observations and experiments carried out in our solar system, among which there are direct gravitational wave astronomy, frame dragging and tests of gravitational theories from solar system and spacecraft observations. This book explores John Archibald Wheeler's seminal and enduring contributions in relativistic astrophysics and includes: the General Theory of Relativity and Wheeler's influence; recent developments in the confrontation of relativity with experiments; the theory describing gravitational radiation, and its detection in Earth-based and space-based interferometer detectors as well as in Earth-based bar detectors; the mathematical description of the initial value problem in relativity and applications to modeling gravitational wave sources via computational relativity; the phenomenon of frame dragging and its measurement by satellite observations. All of these areas were of direct interest to Professor John A. Wheeler and were seminally influenced by his ideas.