IACG was originally started as a forum for the four space agencies in the world which were planning to send explorers to Halley's comet. Its aim was to allow world scientists to co-operate on close observation of the comet on its expected return in the mid 1980s. The parties discussed close international partnership and co-operation on comet science and exploration missions. The four agencies are:

• NASA: National Aeronautics and Space Administration (USA)
• ESA: European Space Agency
• Intercosmos (space union of the former USSR and East European countries)
• ISAS (Institute of Space and Astronautical Science of Japan: the present ISAS of JAXA)

IACG stands for “Inter-Agency Consultative Group,�Ethe formal name at the conference's inauguration. In short, the conference was a “space science summit�Ewhere representatives (Heads of Delegations) from the four agencies could converse. As discussions included subjects requiring special knowledge of diverse fields, the representatives were accompanied by specialists from their respective agencies.

In 1985, the former ISAS (currently ISAS of JAXA) launched two Halley's comet explorers, SAKIGAKE and SUISEI. These were as successful as GIOTTO (ESA), VEGA (Intercosmos) and ICE (NASA) and attracted the world's attention to Japan's space science. The IACG played an important role in this co-operative effort and the four agencies took turns hosting its annual conference. After Halley's comet passed in 1986, the IACG had a summary meeting. It is well known that, after the meeting, Pope Paul II invited all the attendees to the Vatican Palace.

At the IACG meeting in Padova in 1986, it was proposed that the group, which had achieved such a brilliant international collaboration, should continue to co-operate in specific subjects in the field of space science. Thus, the Inter-Agency Consultative Group for Space Science (IACG) was reborn.

The new IACG started with solar-terrestrial physics (space-plasma physics) as its subject for co-operation. At the time, many missions were scheduled to launch for space-plasma research between the Sun and Earth. It is well known that ISAS's spacecrafts, AKEBONO, YOUKOU and GEOTAIL, are still active and providing valuable data along with dozens of missions by other foreign space agencies.

After the break-up of the Soviet Union, the USSR-centered Intercosmos space scientist group became the Russian Space Agency (RSA), and this body now sends a representative to the IACG. The core of the group is the Space Research Institute (IKI) in Moscow, with which ISAS keeps close contact.

When the world stopped launching solar-terrestrial science missions in 1996, the IACG met in Florida and adopted solar-system exploration as the next subject of international cooperation. The current organizational sections of IACG were formed then: four working groups (WG) and three panels (P) were created to discuss major co-operations under the plenary assembly. The subjects allotted to the sections are:

While a remarkable example of international co-operation, space science around the world is also an area intense competition. Needless to say, an accurate knowledge of world trends in space science is vital for the balanced development of Japan's space science. Although Japan's space science has followed its own path of internal development on themes suitable to the era, future missions should not be decided with a narrow outlook. Instead, they should be decided taking into consideration the state of world space-science development and global common issues. IACG's primary significance was that it provided opportunities to acquire accurate knowledge of the world's latest space science through discussions with the world's Topscientists from member agencies.

Japanese space science, which started later than other member countries, reached the world level much faster than expected. This is obvious from the fact that ISAS now holds an important position in IACG. Japanese space science has led the world with its remarkable achievements in the fields of X-ray astronomy, space plasma physics, solar physics and radio astronomy. With the introduction of new M-V rocket, we have embarked on solar-system exploration and are tackling ambitious missions in planetary science. Thus, it may be said that ISAS has an important international role to increase further its world leadership, and not just stay an IACG member. This is the secondary significance of IACG

At the beginning of 21st century, Roger Bonnet, ESA's Director of Science, retired after playing a leading role from the beginning of IACG. At the same time, it became apparent that NASA did not fully appreciate IACG. These factors caused a rapid decline in IACG participation from the 2000 meeting onward, with activities tapering off until the IACG framework had almost disappeared. As the “new age of space exploration�Estarted, however, there is an earnest desire for a place where scientists, including decision-makers in the space-science community, can talk and discuss freely.