1) A robot may not injure a human being or, through inaction, allow a human being to come to harm.
2) A robot must obey the orders given to it by human beings, except where such orders would conflict with the First Law.
3) A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws.
http://www.telegraph.co.uk/science/space/9788827/Humanoid-robot-pictured-on-International-Space-Station.html (http://www.telegraph.co.uk/science/space/9788827/Humanoid-robot-pictured-on-International-Space-Station.html)
Once they make it mobile, R2 could work as an avatar.
Controlled from within the ISS or a ground station.
That may be cheaper than trying to train it as a diagnostic droid and they would never have to worry about a malicious 'Kill All Humans' subroutine uploaded from Skynet. :)