This movie came out in the 80's or early 90's. A crew aboard a space station notice a satellite orbiting close to them and find out it's actually a Chinese orbiting nuclear weapon. They spacewalk and disable it.
I believe this is the 1971 movie 'Earth II' - the plot includes the Chinese nuke being disabled by spacewalkers.
A Russian satellite goes off course. It turns out the satellite's navigation system was designed by Eastwood's character and then stolen by the Russians. So NASA gets the crew back together and they blast off on a space shuttle to fix the satellite.
Once in space...
...they find out the satellite is actually a malfunctioning nuclear missile platform, which is in danger of launching its missiles. They have to prevent it from reentering the atmosphere.