Project: datamanagement
Issue DM-1333: resolve factor of two difference in GaussianFlux
After changing the implementation of GaussianFlux to use the shape slot rather than estimate the shape itself by re-running the SdssShape code, Perry saw a 5-15% difference in the fluxes (I'm not sure of the sign). The new behavior (using the shape) is consistent with what we'd have gotten with the old code when the little-used "fixed" config option was enabled (not surprising, as that just looked up the SdssShape measurement by name, instead of via slots). I suspect the difference is coming in because of the factor of two between SdssShape's "raw" measurements - the actual Gaussian-weighted moments - and the factor of 2 it applies to make its measurements equivalent to ideal unweighted moments. The correct weight function to use for GaussianFlux includes this factor of 2 (i.e. it's larger than the "raw" moments), and it's likely either the old code wasn't including this or the new code isn't. We need to determine which one, and if necessary, fix the new code.
Story points: 2