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  1. Data Management
  2. DM-12058

Investigate PSF problems found in MEDS generation

    Details

    • Type: Story
    • Status: To Do
    • Resolution: Unresolved
    • Fix Version/s: None
    • Component/s: meas_extensions_psfex
    • Labels:
      None

      Description

      In creating MEDS files for HSC data, Erin Sheldon found some problematic PSF models. This ticket is to investigate where the problem is coming from.

        Attachments

        1. e1_res.png
          e1_res.png
          39 kB
        2. mask.png
          mask.png
          618 kB
        3. problem_psf.png
          problem_psf.png
          21 kB
        4. rho1_1am.png
          rho1_1am.png
          53 kB
        5. rho1.png
          rho1.png
          46 kB
        6. size_res_vs_size.png
          size_res_vs_size.png
          66 kB
        7. size_res.png
          size_res.png
          39 kB

          Issue Links

            Activity

            rearmstr Bob Armstrong created issue -
            rearmstr Bob Armstrong made changes -
            Field Original Value New Value
            Attachment problem_psf.png [ 29990 ]
            Hide
            rearmstr Bob Armstrong added a comment -

            Here is an example PSF image of the problems that are being seen.

            Show
            rearmstr Bob Armstrong added a comment - Here is an example PSF image of the problems that are being seen.
            swinbank John Swinbank made changes -
            Epic Link DM-10382 [ 32101 ]
            swinbank John Swinbank made changes -
            Team Data Release Production [ 10301 ]
            rearmstr Bob Armstrong made changes -
            Attachment mask.png [ 30021 ]
            Hide
            rearmstr Bob Armstrong added a comment -

            There appear to be a couple of issues going on:

            • Cases where there are too few stars to constrain the psf model. Things get especially bad when the PSF is interpolated into regions where there are no stars. This will be problematic in HSC for the some of the outer CCDs that are heavily vignetted. We could consider requiring a minimum number of PSF stars for an image to be used.
            • There are artifacts in the PSF models due to the attempt to mask out neighbors. Below is an example of the full postage stamps on the left and the masked image fed to psfex on the right. We could potentially avoid these by using the deblended images or by removing them out. Some preliminary numbers from HSC suggest that 75% of stars are isolated.

            Show
            rearmstr Bob Armstrong added a comment - There appear to be a couple of issues going on: Cases where there are too few stars to constrain the psf model. Things get especially bad when the PSF is interpolated into regions where there are no stars. This will be problematic in HSC for the some of the outer CCDs that are heavily vignetted. We could consider requiring a minimum number of PSF stars for an image to be used. There are artifacts in the PSF models due to the attempt to mask out neighbors. Below is an example of the full postage stamps on the left and the masked image fed to psfex on the right. We could potentially avoid these by using the deblended images or by removing them out. Some preliminary numbers from HSC suggest that 75% of stars are isolated.
            price Paul Price made changes -
            Component/s meas_extensions_psfex [ 10734 ]
            jbosch Jim Bosch made changes -
            Link This issue relates to DM-12410 [ DM-12410 ]
            rearmstr Bob Armstrong made changes -
            Attachment size_res.png [ 30152 ]
            rearmstr Bob Armstrong made changes -
            Attachment e1_res.png [ 30153 ]
            rearmstr Bob Armstrong made changes -
            Attachment rho1.png [ 30154 ]
            rearmstr Bob Armstrong made changes -
            Attachment rho1_1am.png [ 30155 ]
            rearmstr Bob Armstrong made changes -
            Attachment size_res_vs_size.png [ 30156 ]
            Hide
            rearmstr Bob Armstrong added a comment - - edited

            I've tried to test the impact of the masking problem in the data by doing a separate run where I throw out any star that has masking. To increase the number density of stars I set the reserved fraction to zero. This results in roughly the same number of stars as the original settings. I processed 40 randomly selected i-band visits and then compared some different diagnostics.

            Rho1 averaged over all visits:

            Rho1 @ 1 arcmin for each visit:

            This shows very little difference when using the masked objects.

            Show
            rearmstr Bob Armstrong added a comment - - edited I've tried to test the impact of the masking problem in the data by doing a separate run where I throw out any star that has masking. To increase the number density of stars I set the reserved fraction to zero. This results in roughly the same number of stars as the original settings. I processed 40 randomly selected i-band visits and then compared some different diagnostics. Rho1 averaged over all visits: Rho1 @ 1 arcmin for each visit: This shows very little difference when using the masked objects.
            yusra Yusra AlSayyad made changes -
            Epic Link DM-10382 [ 32101 ] DM-12729 [ 36328 ]
            yusra Yusra AlSayyad made changes -
            Epic Link DM-12729 [ 36328 ] DM-14405 [ 79812 ]
            yusra Yusra AlSayyad made changes -
            Epic Link DM-14405 [ 79812 ] DM-16678 [ 235238 ]
            swinbank John Swinbank made changes -
            Epic Link DM-16678 [ 235238 ] DM-20164 [ 323028 ]
            yusra Yusra AlSayyad made changes -
            Epic Link DM-20164 [ 323028 ] DM-21252 [ 414682 ]
            yusra Yusra AlSayyad made changes -
            Epic Link DM-21252 [ 414682 ] DM-22588 [ 427655 ]
            yusra Yusra AlSayyad made changes -
            Epic Link DM-22588 [ 427655 ] DM-23740 [ 431397 ]
            yusra Yusra AlSayyad made changes -
            Epic Link DM-23740 [ 431397 ] DM-25271 [ 435631 ]

              People

              • Assignee:
                rearmstr Bob Armstrong
                Reporter:
                rearmstr Bob Armstrong
                Watchers:
                Bob Armstrong
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                Dates

                • Created:
                  Updated:

                  Summary Panel