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  1. Data Management
  2. DM-15635

Investigate filter throughput for DcrCoadds

    Details

      Description

      The prototype DcrCoadd generation code used the same filter transmission curve as the input simulations, and was able to recover the input spectra of individual simulated sources accurately. The new stackified DcrCoadds use a simple top hat transmission curve (until DM-13668 is completed), and are not able to recover the input simulated source spectra as well. This ticket is to investigate the effect of the filter transmission on the accuracy of the recovered source spectra.

        Attachments

        1. spectrum_N180_G5296.png
          spectrum_N180_G5296.png
          48 kB
        2. spectrum_N188_G5235.png
          spectrum_N188_G5235.png
          47 kB
        3. spectrum_N192_K4838.png
          spectrum_N192_K4838.png
          52 kB
        4. spectrum_N196_K4494.png
          spectrum_N196_K4494.png
          48 kB
        5. spectrum_N199_F6478.png
          spectrum_N199_F6478.png
          51 kB
        6. spectrum_N200_G5957.png
          spectrum_N200_G5957.png
          49 kB
        7. spectrum_N204_K4087.png
          spectrum_N204_K4087.png
          46 kB

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            Hide
            sullivan Ian Sullivan added a comment -

            Note that this includes a pull request in

            {pipe_tasks}

            , which will probably not get a link from JIRA.

            This includes three slightly unrelated commits that together improve the accuracy of building a DcrModel. This allows the model to smoothly converge even with greater numbers of subfilters, which mitigates the problem of residual DCR across a subfilter for high airmass observations.

            Show
            sullivan Ian Sullivan added a comment - Note that this includes a pull request in {pipe_tasks} , which will probably not get a link from JIRA. This includes three slightly unrelated commits that together improve the accuracy of building a DcrModel. This allows the model to smoothly converge even with greater numbers of subfilters, which mitigates the problem of residual DCR across a subfilter for high airmass observations.
            Hide
            mrawls Meredith Rawls added a comment -

            This mostly looks OK, but I left some comments on GitHub I'd like to see addressed before I mark it Reviewed.

            You shared a plot on Slack that related to this and illustrated how nicely the new filter midpoint worked, didn't you? I'd love to see before/after comparison plots on this ticket for posterity!

            Show
            mrawls Meredith Rawls added a comment - This mostly looks OK, but I left some comments on GitHub I'd like to see addressed before I mark it Reviewed. You shared a plot on Slack that related to this and illustrated how nicely the new filter midpoint worked, didn't you? I'd love to see before/after comparison plots on this ticket for posterity!
            Hide
            sullivan Ian Sullivan added a comment -

            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.

            Show
            sullivan Ian Sullivan added a comment - 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.
            Hide
            mrawls Meredith Rawls added a comment -

            Looks great! Please just fix the one mismatched reference I found (see GitHub). Thanks for all the plots.

            Show
            mrawls Meredith Rawls added a comment - Looks great! Please just fix the one mismatched reference I found (see GitHub). Thanks for all the plots.
            Hide
            sullivan Ian Sullivan added a comment -

            It looks like the "stackified" code is working as well or better than the prototype implementation now.

            Show
            sullivan Ian Sullivan added a comment - It looks like the "stackified" code is working as well or better than the prototype implementation now.

              People

              • Assignee:
                sullivan Ian Sullivan
                Reporter:
                sullivan Ian Sullivan
                Reviewers:
                Meredith Rawls
                Watchers:
                Ian Sullivan, John Swinbank, Meredith Rawls
              • Votes:
                0 Vote for this issue
                Watchers:
                3 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved:

                  Summary Panel