Greg Egan on Nostr: Yes, and specifically I say in the post that we’re measuring things in the ...

Yes, and specifically I say in the post that we’re measuring things in the reference frame of a tidally locked body that always points towards the central mass, so we know exactly how fast it’s rotating around its own axis.

Of course you could work this out in any frame you like, but I find it intuitively easier to linearise the central force after choosing a specific frame, and it’s one whose test-particle trajectories I studied very closely when I was looking at the Newtonian, Kerr and Schwarzschild metric versions for “Incandescence.”

And in this case we also have the advantage that the triangle the spacecraft form lies on a circle that is fixed in the “tidally locked hollow asteroid” frame.