from Gaia to gravity

In what research time was left after completing my NSF proposal (hooray!), I worked on the theoretical question of how one might infer the gravitational forces or gravitational potential of the Milky Way from the Gaia observations. The problem is extremely non-trivial, because Gaia only measures positions and velocities, but it is accelerations that constrain the gravitational potential or forces. As I have said before, all important questions in science are ill-posed; the challenge is to come up with well-posed approximations to the ill-posed questions. I think there might be some well-posed questions to ask with Gaia, but it is hard to write them down even if you are allowed to assume that the potential is time-independent and azimuthally symmetric (which you aren't).