optimal transport distance interpolator

[jmeyers314]

Here's another potentially interesting PSF interpolator: https://arxiv.org/pdf/1703.06066.pdf . I have a slight suspicion that this one may be more useful for space than for ground, but would be happy to be proven wrong. Also, do we have any aspirations on making Piff useful for space?

[rmjarvis]

Interesting. Definitely worth trying, but I think you're right that it will be more applicable to space PSFs without the atmospheric component. I've been focusing on ground PSFs for now, since the need is more pressing, but I do hope that Piff will eventually be useful for space observations as well.