At the opening of the "Third Meeting on Celestial Mechanics - CELMEC III", strong sensations hit our minds. The conference (18-22 June 2001) was being held in Villa Mondragone, a beautiful complex of buildings and gardens located within the township of Monte Porzio Catone, on the hills surrounding Rome. A former papal residence, the building has been recently restored by the University of Rome "Tor Vergata" to host academic activities and events. The conference room is called "Salone degli Svizzeri": here, Gregory XIII, on February 24, 1582, gave its sanction to the reform of the Julian calendar and declared officially in use the calendar still adopted nowadays. The magnificent high walls and tall ceiling strongly resounded, giving to our voice a peculiar Vatican sound, which took us by surprise. May be - we thought - a distant echo of the very words of Gregory XIII proclaiming the modem calendar was still haunting the room. Around us, in the audience, many countries were represented, thus indicating that the idea of putting together the three "souls" of modem Celestial Mechanics - perturbation theories, solar and stellar system studies, spaceflight dynamic- had been successful. CELMEC III is in fact the latest of a series of meetings (the first two editions took place in 1993 and 1997 in L' Aquila, Italy) whose aim is to establish a common ground among people working in Celestial Mechanics, yet belonging to different institutions such as universities, astronomical observatories, research institutes, space agencies and industries.

GOCE: The Earth Gravity Field by Space Gradiometry.- Symmetries and Rank Deficiency in the Orbit Determination Around Another Planet.- The Rotation of Europa.- Resonant Fly-By Missions to Near Earth Asteroids.- Analysis of the Space Debris Impacts Risk on the International Space Station.- On the Stability of the Terrestrial Planets as Models for Exosolar Planetary Systems.- Generalized Averaging Principle and the Secular Evolution of Planet Crossing Orbits.- Probing the Nekhoroshev Stability of Asteroids.- Resonant Periodic Motion and the Stability of Extrasolar Planetary Systems.- Stability in the Full Two-Body Problem.- Geometry of Chaos in Models of Stellar Dynamics.- Order and Chaos in Self-Consistent Galactic Models.- On the Relationship Between Fast Lyapunov Indicator and Periodic Orbits for Continuous Flows.- Effective Hamiltonian for the D¿Alembert Planetary Model Near a Spin/Orbit Resonance.- A Systematic Study of the Stability of Symmetric Periodic Orbits in the Planar, Circular, Restricted Three-body Problem.- Estimate of the Transition Value of Librational Invariant Curves.- Ideal Resonance Problem: The Post-PostPendulum Approximation.- The Web of Periodic Orbits at L4.- Long-term Stability Analysis of Quasi Integrable Degenerate Systems Through the Spectral Formulation of the Nekhoroshev Theorem.- How the Method of Minimization of Action Avoids Singularities.- Non-existence of the Modified First Integral by Symplectic Integration Methods II: Kepler Problem.- Dynamical Evolution of the Adeona and Gefion Asteroid Families.- On the Expansion of the External Gravitational Potential in Spheroidal Harmonics.- Periodic Orbits Approximation of Analyticity Domains of Invariant Curves.- Low ?V Orbit Insertion in Interplanetary Missions.- Long-Term Dynamics of the Tunguska Cosmic Body.- On the Triangular Points of the Sun-Jupiter System.- Inter-Comparisons Between Numerical Integrations and Analytical Theory for the Solar System.- The Central Manifold for the Collinear Libration Points.- Periodic Orbits of Trans-Neptunian Objects at the 2/3 and 3/4 Resonances.- Rotation of Natural Shaped Satellites and their Orbital Motion.- From Kolmogorov¿s Normalization Algorithm to the Orbits in the Three-Body Planetary Problem.- Dynamical Behaviour of Asteroids in the Region a