K2 pointing model

Imagine a strange "game": A crazy telescope designer put thousands of tiny pixelized detectors in the focal plane of an otherwise stable telescope and put it in space. Each detector has an arbitary position in the focal plane, orientation, and pixel scale, or even non-square (affine) pixels. But given the stability, the telescope's properties are set only by three Euler angles. How can you build a model of this? Ben Montet (Harvard CfA), Foreman-Mackey, and I worked on this problem today. Our approach is to construct a three-dimensional "latent-variable" space in which the telescope "lives" and then an affine transformation for each detector patch. It worked like crazy on the K2 data, which are the data from the two-wheel era of the NASA Kepler satellite. Montet is very optimistic about our abilities to improve both K2 and Kepler photometry.

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