I've attached several plots of example measured spectra with the different options added in this ticket turned on or off. The largest change was due to multiplying the measured spectrum by the LSST filter throughput in the final analysis. In the plots, this is seen by comparing "corrected base" to the original "uncorrected base." The filter throughput correction is included in all of the other measured values.
Two of the three modified options are plotted:
- "gain": which involves slowly increasing the gain as the number of iterations increases. This results in slightly larger changes between iterations (after the first few) and allows the model to converge faster.
- "split": which splits each subfilter in half during forward modeling and averages the result of DCR shifting between the two halves. This partially accounts for non-negligible DCR across a subfilter, without increasing the number of free parameters.
The best results are obtained by using both options together.
The "useModelWeights" option is not plotted, because it's results are indistinguishable from the base plots for three subfilters. It's benefit comes for higher numbers of subfilters where the model previously had trouble converging due to feedback between noisy pixels. With this new option turned on, the model converges smoothly with five subfilters.