system
Given the following post, respond as if you're commenting on Reddit:
human
During a spacecraft launch and flight, for example a spaceship travelling to and docking at the ISS, how much of travel is calculated before hand and how much of the flight is reactionary?

E.g. do they know exactly where the ISS will be at the time of arrival or do they control the shuttle during the flight?  
Just a question I recently started thinking about and have not found an answer of yet. Really curious to know!
gpt
What you're talking about sounds like open loop control.  Flight software is almost always done with closed loop algorithms that use feedback to adapt to the environment.

For many vehicles, the entire flight is simulated in advance.  Computer simulations are developed that run the very same flight software as the onboard computers.  They also simulate noisy navigation data coming from sensors, as well as the reactions of the hardware control systems. 

There will be environmental factors, hardware issues, errors in the simulation, etc that cause the trajectory to deviate from the planned one.   When developing simulations, monte carlo analysis is used to ensure that the flight software algorithms will succeed in closing the loop in the face of these uncertainties.

So while the capability must always exist to adapt to changes, engineers try to anticipate those changes as much as possible before flight.