My bet would have been that they don't use it at all.
First, because ... is there an actual circle anywhere in what they do?
Even ellipses are simplified approximate solutions to the N-body problem. Not to mention what happens when you apply a burn force.
Second because I would have imagined that most of what they do involves integrating PDE's where if, by chance, PI gets involved, it'll be implicitly computed by the integration engine.
First, because ... is there an actual circle anywhere in what they do?
Even ellipses are simplified approximate solutions to the N-body problem. Not to mention what happens when you apply a burn force.
Second because I would have imagined that most of what they do involves integrating PDE's where if, by chance, PI gets involved, it'll be implicitly computed by the integration engine.
But hey, happy to be proved wrong.