Ian Dell'Antonio (appears not to be on Jira) described a jointcal bug on slack where all of the on-sky residuals after initialization were NaN, but the tangent plane values were reasonable. The existing debug information jointcal can provide was not enough to readily narrow down the source of this; there may be something pathologically wrong with the initial model. To help debug such problems, we need a way to write out the initial model to disk. A writeInitialModel option in the jointcal config that just dumps text files for each model component would be a good start: I think all of the AstrometryTransforms have useful string representations.