Membership in the IOAG is open to all international, civilian space agencies having a substantial scientific space program, which maintain significant communication assets, and wish to be interoperable with other agencies. Admission of a space agency that does not have significant communication assets may be made on a case-by-case basis, provided that its space program includes missions which lie within an area of interest of several IOAG Agencies and where coordination or cross-support are important objectives.
There are two types of membership: Full Members and Observer Members.