Institute of Technology Bandung (ITB), Indonesia and Gunma Astronomical Observatory (GAO), Japan have been proceeding with several programmes of mutual collaboration in the fields of astronomical research and education since 2002. ITB with Bosscha observatory has a great interest in education of astronomy for public people as well as in the university education and research of their own, and GAO is a public observatory operated by Gunma prefecture local government equipped with a 150-cm reflector and some smaller telescopes, which are capable of scientific research of high grade. We will report some of our cooperative activities including the remote accessing of the telescopes of each observatory by each other, which can provide opportunities for astronomical experiences of the opposite hemisphere for various people of each country. Some scientific collaboration works such as common instruments and data analysis systems developed on both sites are also reported.

As for comets 619 comets received names from July 2002 to June 2005. Of this naming 76 percent are SOHO comets and 11 percent include the name of the LINEAR project. A revision of the guidelines for naming comets has been completed in March 2003. The assistance of the director of CBAT, Daniel W. E. Green, in redrafting these guidelines was much appreciated by the committee.

Thirty five grants were made during the triennium October 1, 1996 to September 30, 1999. The astronomer, home country, and host country are listed below.

The Working Group often overlaps in responsibilities with other Commissions, particularly with Commission 46. Some projects (e.g. TAD) may begin on the initiative of our Group but are maintained by Commission 46. TAD programmes are now running in Viet Nam and Central America and one will begin soon in Morocco. Preliminary inquiries have been received from other countries.

In this paper the author presents evidences showing that for most of the asteroids the motions are stable in the sense that they never approach major planets very closely and explains about mechanisms to avoid very close approaches by investigating the variations due to the secular perturbations of the eccentricities as functions of the arguments of perihelion, particularly, for asteroids with high eccentricities and inclinations. It is believed that some kinds of dynamical evolution processes have made the asteroid motions stable. The author shows also that there were some kinds of collisions among asteroids in the past which produced families and present distribution of asteroids as there are very faint asteroids only near Kirkwood gaps.

In the past triennium members of the Commission 20 have been very active in studying positions and motions of minor planets, comets and satellites including rings by observational and theoretical investigations, as it is described in this report In fact observers have been producing tremendous amount of astrometric data, much more than we could imagine twenty years ago, when we heard many complains and appeals to observers for needs of more observations, particularly, for minor planets and satellites. Technically, several new devices to detect faint objects and to measure their positions more effectively, have been developed. Theoreticians have faced many interesting and important problems to explain observational facts with several powerful methods developed recently.

At the XIXth General Assembly our Commission held two meetings during the course of which the following papers were presented:

The present report covers the period 1 February 1985 to 30 November 1987. During this period a total of 23 travel grants were awarded as follows:

Celestial Mechanics has undergone, in the past three years, a considerable development that has been marked by a significant increase of published papers and by the recent organization of several specialized colloquia or symposia. The reasons of this increase of interest may be found among the following circumstances:

1. - The discovery of new dynamical situations in the Solar system: ellipticity of ringlets, shepherd satellites.

2. - The increase of interest in the problem of the dynamical evolution of the solar system or of its subsystems.

3. - The present necessity to include relativistic effects in the theory of motion of celestial bodies.

4. - New promising results in the analysis of the properties of dynamical systems.

Interest in minor planets and comets continued to grow during the triennium, sparked in part by the highly successful 1983 mission of the Infrared Astronomy Satellite (IRAS) as well as by activities associated with the return of P/Halley and the first spacecraft missions to comets. A trial of the Astrometry Network of the International Halley Watch (IHW) on P/Crommelin was quite successful. Yet with an increasing need for precise ephemerides, there continued to be concern for acquisition and timely reporting of astrometric observations of even the best known comets.

In the past three years progress of celestial mechanics research was as rapid as in the previous decade. In fact now new theories of planetary and lunar motions which have nearly the same accuracy as those of the most precise observations have become available after a decade effort and new thories of some of natural satellite motions have been developed by several authors. Many papers on artificial satellite motions from several aspects were still published and more precise expressions for relativistic effects were derived.

For observed positions ofi artificial satellites and their orbital elements, many kinds of reference coordinate systems have been available. Some are more convenient for reductions of observations, while others are more convenient for analyzing the orbital elements for geodesy. In this review paper, perturbations produced owing to the adoption of diffrent kinds of reference systems are discussed.

The first-order theory of secular perturbations for an asteroid indicates that the secular motions of the longitudes of the perihelion and of the ascending node have an equal absolute value with opposite signs, that is, , where b is a function of the semimajor axis and has the disturbing mass as a factor, if the eccentricity and the inclination are sufficiently small so that their squares are of the order of the disturbing mass and if there is no commensurable relation between the mean motions of the asteroid and the disturbing planet. Thus Π + Θ is a stable quantity according to the first-order theory, therefore, the origin of families of asteroids has been discussed by using the data for distribution of Π + Θ as well as those for dispersions of other orbital elements of asteroids belonging to a family.

The most exciting feature of contemporary celestial mechanics is the close interaction with three of the most dramatic engineering achievements of our time: the electronic computer, artificial celestial objects, and the precise measurement of distances in the solar system. The last two provide new information for and make new demands on celestial mechanics and the former provides an effective means of response. These developments have also stimulated people with backgrounds other than celestial mechanics to make contributions in the field.

Since the last meeting of the Union, the use of the computer for literal theoretical developments has become effective and widespread.

The creation of artificial celestial objects not only requires the services of celestial mechanics but provides the means of obtaining new measurements that may throw light on the physical laws that govern the motion of celestial objects. In other words, we can now perform experiments as well as observe.