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  1. Data Management
  2. DM-3057

KPM Measurement: Relative Astrometry (AM1), FY15

    Details

    • Type: Epic
    • Status: Done
    • Resolution: Done
    • Fix Version/s: None
    • Component/s: None
    • Labels:
    • Epic Name:
      KPM: AM1, FY15
    • WBS:
      02C.04
    • Team:
      Data Release Production
    • Cycle:
      Summer 2015

      Description

      This will be measured on precursor data (almost certainly from HSC, via DM-2380) using the following procedure:

      • Run visit-level processing (i.e. ProcessCcdTask, probably via the new HSC driver ported on DM-3368).
      • Run relative astrometric calibration (i.e. meas_mosaic, DM-2674).
      • Select bright stars and match across visits (new scripts, mostly delegating to existing code). Just selecting the stars used for PSF determination would probably work.
      • Generate pairs of objects with separation near the target (5' for this issue, 20' or 200' for DM-3064 and DM-3071). Bin widths will have to be determined, as that's not included in the requirement specification. Will require new code.
      • Plot separation deltas (difference from per-pair mean separation) vs. magnitude; measure RMS and outliers in magnitude bins.

      This requirement is specified only for r and i band.

      The same procedure will be used for the AM1 (DLP-310), AM2 (DLP-311, DM-3064), and AM3 (DLP-312, DM-3071) measurements for this cycle.

        Attachments

        1. D_5_ARCMIN_16.0-16.5.jpg
          D_5_ARCMIN_16.0-16.5.jpg
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        2. D_5_ARCMIN_16.5-17.0.jpg
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          323 kB
        3. D_5_ARCMIN_17.0-17.5.jpg
          D_5_ARCMIN_17.0-17.5.jpg
          324 kB
        4. D_5_ARCMIN_17.5-18.0.jpg
          D_5_ARCMIN_17.5-18.0.jpg
          319 kB
        5. D_5_ARCMIN_18.0-18.5.jpg
          D_5_ARCMIN_18.0-18.5.jpg
          328 kB
        6. D_5_ARCMIN_18.5-19.0.jpg
          D_5_ARCMIN_18.5-19.0.jpg
          328 kB
        7. D_5_ARCMIN_19.0-19.5.jpg
          D_5_ARCMIN_19.0-19.5.jpg
          326 kB
        8. D_5_ARCMIN_scatter.jpg
          D_5_ARCMIN_scatter.jpg
          898 kB
        9. Deq5ARCMIN.jpg
          Deq5ARCMIN.jpg
          311 kB
        10. generateMatches.py
          4 kB
        11. jimBoschScript.py
          4 kB
        12. KPMScript_hist.py
          5 kB
        13. KPMScript_scatter.py
          5 kB
        14. KPMScript1.py
          4 kB
        15. ListOfLists.pkl
          6.47 MB
        16. Utilities.py
          8 kB

          Issue Links

            Activity

            Hide
            vpk24 Vishal Kasliwal [X] (Inactive) added a comment -

            David Nidever [X] The code used to generate the plots is attached to this ticket.

            jimBoschScript.py does the matching and generates ListOfLists.pkl which is a python pickled object consisting of the required data for all the matches.

            KPMScript_hist.py & KPMScript_scatter.py produce the required scatter plots and histograms from ListOfLists.pkl i.e. you can avoid re-running the jimBoschScript.py and just directly use the .pkl object. This may be your best bet because the jimBoschScript.py needs HSC data to run anyway. You can change the matching parameters in the two KPMScripts to make the plots for the required annulus etc...

            Hope this helps

            Show
            vpk24 Vishal Kasliwal [X] (Inactive) added a comment - David Nidever [X] The code used to generate the plots is attached to this ticket. jimBoschScript.py does the matching and generates ListOfLists.pkl which is a python pickled object consisting of the required data for all the matches. KPMScript_hist.py & KPMScript_scatter.py produce the required scatter plots and histograms from ListOfLists.pkl i.e. you can avoid re-running the jimBoschScript.py and just directly use the .pkl object. This may be your best bet because the jimBoschScript.py needs HSC data to run anyway. You can change the matching parameters in the two KPMScripts to make the plots for the required annulus etc... Hope this helps
            Hide
            nidever David Nidever [X] (Inactive) added a comment -

            I'll try to look at this. I hadn't realized there was progress on this front since Bremerton. It would be useful to have the code that is being used to derive these metrics.

            Show
            nidever David Nidever [X] (Inactive) added a comment - I'll try to look at this. I hadn't realized there was progress on this front since Bremerton. It would be useful to have the code that is being used to derive these metrics.
            Hide
            zivezic Zeljko Ivezic added a comment -

            Yes, Robert already mentioned this new 3mas goal to me some time ago. Before we can
            propose to change the SRD, we need to understand quantitatively how whatever metric
            was used depends on the actual value of that spec. I am puzzled by the following result.
            To get to 3mas, and using error ~ FWHM/SNR, we need SNR ~ 200 or larger. The faintest
            galaxies in our gold sample (i<25) will have SNR~20. So we need to go 2.5 mag brighter
            to even theoretically be able to achieve 3mas. But if you go 2.5 brighter, and the cumulative
            counts go down as logN = 0.31*(i-25), only about 15% of galaxies in the gold sample could
            theoretically have relative astrometric errors as small as 3 mas. Hence, based on this simple
            initial analysis, I conclude that 3 mas is an overkill. To convince me that I am wrong, we will
            need a more quantitative description of the origin of this 3 mas requirement.

            Show
            zivezic Zeljko Ivezic added a comment - Yes, Robert already mentioned this new 3mas goal to me some time ago. Before we can propose to change the SRD, we need to understand quantitatively how whatever metric was used depends on the actual value of that spec. I am puzzled by the following result. To get to 3mas, and using error ~ FWHM/SNR, we need SNR ~ 200 or larger. The faintest galaxies in our gold sample (i<25) will have SNR~20. So we need to go 2.5 mag brighter to even theoretically be able to achieve 3mas. But if you go 2.5 brighter, and the cumulative counts go down as logN = 0.31*(i-25), only about 15% of galaxies in the gold sample could theoretically have relative astrometric errors as small as 3 mas. Hence, based on this simple initial analysis, I conclude that 3 mas is an overkill. To convince me that I am wrong, we will need a more quantitative description of the origin of this 3 mas requirement.
            Hide
            mjuric Mario Juric added a comment -

            Vishal Kasliwal [X], thanks for reminding me! Regarding Mike's comment – we've been aware of that for a while but didn't have the time to act on it yet.

            If he's right (and I think he is), it will necessitate a tightening of the SRD. That makes it first my problem (to prove this needs to be done), and then a PST problem (to further review it and assess whether it can be done, given what we've built so far). I'll add it on my TODO list (I'd expect to be able to take it up sometime early next year).

            Zeljko Ivezic, take a look some ~three comments up, this is about having to tighten the astrometry requirements to ~3mas (just FYI at this point).

            Show
            mjuric Mario Juric added a comment - Vishal Kasliwal [X] , thanks for reminding me! Regarding Mike's comment – we've been aware of that for a while but didn't have the time to act on it yet. If he's right (and I think he is), it will necessitate a tightening of the SRD. That makes it first my problem (to prove this needs to be done), and then a PST problem (to further review it and assess whether it can be done, given what we've built so far). I'll add it on my TODO list (I'd expect to be able to take it up sometime early next year). Zeljko Ivezic , take a look some ~three comments up, this is about having to tighten the astrometry requirements to ~3mas (just FYI at this point).
            Hide
            mjuric Mario Juric added a comment -

            John Swinbank et al., the methodology looks sound, but before we close:

            • Are the various scripts that are being used somewhere in a git repository, together with sufficient instructions on how to reproduce the measurements?
            • I think both I and David Nidever [X] should do a more careful code review on them to a) double-check for consistency with the letter and spirit of the SRD requirements and, b) check for any potential mistakes.

            In general, I think David should audit proposed ways to measure KPMs (sorry David ) – it's always good to have another pair of eyes there, as these tests ultimately determine whether we've passed or failed. We'll probably have to have an independent review of them in sometime near the end of construction.

            PS: If it's better from the scheduling point of view, it's fine with me to make the above tasks for FY16 KPM measurements.

            Show
            mjuric Mario Juric added a comment - John Swinbank et al., the methodology looks sound, but before we close: Are the various scripts that are being used somewhere in a git repository, together with sufficient instructions on how to reproduce the measurements? I think both I and David Nidever [X] should do a more careful code review on them to a) double-check for consistency with the letter and spirit of the SRD requirements and, b) check for any potential mistakes. In general, I think David should audit proposed ways to measure KPMs (sorry David ) – it's always good to have another pair of eyes there, as these tests ultimately determine whether we've passed or failed. We'll probably have to have an independent review of them in sometime near the end of construction. PS: If it's better from the scheduling point of view, it's fine with me to make the above tasks for FY16 KPM measurements.

              People

              • Assignee:
                vpk24 Vishal Kasliwal [X] (Inactive)
                Reporter:
                swinbank John Swinbank
                Reviewers:
                Mario Juric
                Watchers:
                David Nidever [X] (Inactive), John Swinbank, Kian-Tat Lim, Mario Juric, Vishal Kasliwal [X] (Inactive), Zeljko Ivezic
              • Votes:
                0 Vote for this issue
                Watchers:
                6 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved:

                  Summary Panel