The European Space Agency works with a tender system: http://emits.sso.esa.int/emits/owa/emits.main
Currently, there are 3 modeling-related tenders in there:
These could be interesting for organizations that provide modeling-related software engineering services. You can also register on an individual basis as an entity: ESA - esa-star registration process
After having done that, you can register as a potential “sub prime” on tenders, which means that a prime can contact you to help with working on a tender. I’ve heard ESA is setting up a matching system to help with that process as well.