[dogscoff]

1000. Never tried to find out. For that reason. Might be worth modding to see.

[EDIT] Only 100 units are allowed in any one sector so you would have to mod to see

You could launch a hundred, retrieve them, launch again, retrieve until utnil you've done a thousand launches, then hit launch again and repeat. Of course, if you've only got one sat on the planet, it could take you a while to set that up...