Fergus, Neil Zimmerman (MPIA), and I chatted on the phone a bit today. Zimmerman wants to write a proposal to build a forward model of a coronographic spectrograph (think P1640 or GPI); he has the intuition (which I share) that if you built such a model, you could calibrate the data far better. Right now calibration is performed before and after observing; the science frames are expected to be in agreement with the calibration meta-data or some interpolation of it, and the data are "corrected" or transformed from the instrument coordinates (two-dimensional pixels) to some calibrated object (three-dimensional imaging spectroscopic boxels). But since flexure and temperature changes can be non-trivial, and since the science frames contain so many photons, it would be better to learn the calibration of the spectrograph from the appropriate combination of the calibration and science data, and it would be better to perform the comparison between models and data at the pixel level. That's a theme of this blog, of course. We discussed what kinds of small, toy, demonstration systems could show this, convincingly enough for a proposal, relevant to the real thing, but easy to set up and use as a little sandbox.