So, Russia hasn't stopped operations on the International Space Station. Soyuz spacecraft will continue to carry cosmonauts and astronauts there, despite growing international tensions on Earth. We can all breathe easy for a moment. Okay, that's done. Now it's time to consider what happens next.

It would seem that things will probably remain on a similar course until 2020. After that, who knows? We have recently celebrated the 70th anniversary of the legendary D-Day that marked the beginning of the end for Nazi Germany.

Now it's time to start planning for another important (if less critical) event: Decision Day for ISS. Russia has stated that it will probably suspend its participation in the International Space Station in 2020, posing serious questions over its entire future. Even without a Russian pull-out, ISS would still be a program with an uncertain course.

Right now, it isn't clear how, or if, the International Space Station will progress after the 2020 mark. It is a decision that cannot be taken by America alone. Several other nations are involved. Removing Russia from the Station will have profound implications for all.

Russia has been the sole provider of crew transport and a major supplier of logistics. Sure, we will probably see at least one US crew transfer vehicle introduced before 2020, and US commercial cargo vehicles will continue to operate. But Europe is rounding off its ATV cargo vehicle program. Japan's promised convoy of HTV cargo ships is also finite. Financial austerity is gripping the space programs of all nations. How can this complex and unstable web of activity be untangled?

The silence from some partners involved in the ISS is curious. It suggests that there is no clear plan of action, and concerns over the future of the program. ISS has been a costly and troublesome project. The pull-out of Russia and the growing age of the Station could serve as effective cues for some nations to cut and run.

This could result in a diminishing stock of participants. As nations leave the project, the political value of ISS will also diminish. The more nations withdraw, the easier it is for the remaining partners to pull out. And eventually, there's nobody left.

ISS could be operated in a scaled-down mode for some time after 2020, possibly by NASA and some of its remaining partners. This could involve smaller crews, with fewer logistics support vehicles. The level of productive work performed on the station will decrease markedly, as the reduced crews will need to spend a higher proportion of their time just maintaining the station itself.

Mechanical failures could increase as the station gets older, and some failures could be difficult to fix. Spare parts launched to the station in the twilight days of the Shuttle program could run out sooner than expected. At some point, it may become impractical to operate the station for engineering reasons.

Prior to the Russian annexation of Crimea, there was talk of extending ISS operations to 2024. This may still be possible, but an extended ISS program won't be as large or as useful as we had originally expected.

Then there's the question of the Russian modules attached to ISS. Some pundits speculate that Russia may detach these modules and use them as the core of an independent Russian station. This is technically possible, but ownership and control of a Russian module built with US money could prove thorny. A full discussion of this point is beyond the scope of this article.

Compensating for the loss of Russian hardware could require the launch of new modules to compensate for their functionality, assuming that there is enough interest in keeping the Station operational.

We still probably have several years of operations to go on ISS in its current format, but this does not change the seriousness of the problem. It takes time to develop plans in spaceflight. It takes even longer to implement them. D-Day for the International Space Station is closer than some people think. Governments and space agencies around the world need to act quickly.

Dr Morris Jones is an Australian space analyst who has written for spacedaily.com since 1999. Email morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email. Dr Jones will answer media inquiries.