The IAU General Assembly (GA) is held every three years and is a unique opportunity to bring astronomers from across the world together for two weeks. The IAU therefore spends a significant fraction of its annual budget to enable wide and diverse participation, by providing many travel grants primarily to young astronomers and astronomers from developing countries. In contrast with some other big unions and societies, the IAU does not use its scientific meetings to provide income for the organization, just the opposite.

By having a General Assembly only once every three years but for a period of two weeks, the IAU aims to optimize a maximum amount of science with minimal travel. The GA program typically consists of six IAU Symposia, a dozen Focus Meetings, Divisions Days, and meetings centered around the IAU Offices and Executive Working Groups, as it does at GA 2022. Therefore, in those two weeks, astronomers not only get to hear and present the latest results in their own fields of expertise, but also have an opportunity to attend symposia and meetings to learn about other areas of astronomy, interact informally with lots of colleagues from across the entire world, make new connections, set up new collaborations, and learn about (and contribute to) IAU's efforts to train young scientists and use astronomy as a tool for education, outreach and development.

In the selection of the host city and country for a GA, the IAU pays special attention to the commitment of the Local Organization to keep the registration fee as low as possible. Due to the pandemic, many conferences have now shifted to a hybrid mode with a mix of in-person and remote presentations. Some people have been surprised that the registration fees of such meetings are not lower, especially since online communication tools appear to be cheap or even free for individuals. But this is not the case for big conferences, and their organizers have to recover those costs somehow. In fact, as stressed also by other organizations, the costs are highest for conferences in hybrid mode since the organizers have to pay both the costs of the venue for two weeks as well as extra costs for recording and broadcasting the live presentations.

The LOC of GA 2022 in Busan has from the very beginning been fully committed to keep registration fees as low as possible. They are now coping with the extra costs of the hybrid format as well as those associated with the postponement of the GA. By asking speakers to pay the full registration fee (note that in-person registration is required to submit oral abstracts, whether in-person or remote), they have made the choice to keep the virtual registration fee low to enable the participation of more colleagues with fewer resources.  

IAU President, on behalf of IAU Officers