elaborating the causal structure of wobble

Lily Zhao (Yale) and Megan Bedell (Flatiron) and I are working on measuring very precise radial velocoties for very small data sets, where (although there are hundreds of thousands of pixels per spectrum) there are only a few epochs of observations. In these cases, it is hard for our data-driven method to separate the stellar spectrum model from the telluric spectrum model—our wobble method makes use of the independent covariances of stellar and telluric features to separate the star from the sky. So we discussed the point that really we should use all stars to learn the (maybe flexible) telluric model). That's been a dream since the beginning (it is even mentioned in the original wobble paper), but execution requires some design thinking: We want the optimizations to be tractable, and we want the interface to be sensible. Time to go to the whiteboard. Oh wait, it's a pandemic.