perform psf and shape tests on DC1

[fjaviersanchez]

@rmandelb suggested here: https://github.com/LSSTDESC/DC2_Repo/issues/33#issuecomment-342885951 some tests that could/should be done with DC1.

• PSF tests (started here: https://github.com/LSSTDESC/SSim_DC1/blob/master/Notebooks/PSF_test.ipynb)

• Other tests using galaxy shapes. (Edited to say these are the tests that take advantage of the absence of a cosmological shear signal.)

[rmandelb]

It would be valuable to use some standard lensing measures of PSF model fidelity, like rho statistics and fractional PSF size errors, since we know how those propagate into shear biases. Since your code already can produce the true PSF and the estimated PSF (i.e., the PSF model at the position of individual objects), it should be quite easy to calculate the rho statistics.

See for example section 3.4 in http://adsabs.harvard.edu/abs/2016MNRAS.460.2245J for the definitions of rho1 through rho5, and how they affect the measured cosmic shear correlation functions. These can use standard shape correlation codes like TreeCorr. You might also advertise this project in the desc-wl channel to see if somebody who regularly calculates these is interested in trying this out, if you do not want to do this yourself?

[fjaviersanchez]

Thanks @rmandelb I'll try to start it myself if I have time before the sprint. In any case, I am creating a project for the hack week in case that there's people interested in doing this :)