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  1. Data Management
  2. DM-8912

Use Gaia to compare absolute astrometry post-jointcal on HSC

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      Description

      The current jointcal tests either use a perfect reference catalog in the fits, and then compare with it, or use an imperfect refcat in the fits, and also compare with it. We believe that much of joincal's improvement is due to its "improving" an imperfect reference catalog, and thus these tests don't tell us whether our understanding is correct, nor whether it really "works" at all, or if it's just over-fitting.

      In order to confirm that jointcal really is causing an improvement by "constraining the reference catalog", we need to compare a perfect reference catalog with the single frame and jointcal astrometric fits performed on a non-perfect reference catalog. Gaia is as closed to perfection as we've got, and the validation datasets have less perfect refcats already.

      Steps:

      1. Download a 3-4 degree radius Gaia catalog at the location of the 4-visit validation_data_hsc data.
      2. Take the jointcal results for the 4-visit HSC validation_data and run plot_jointcal_results.py using the above Gaia data as the reference catalog.
      3. If jointcal "works" as we understand it to, the "absolute astrometry" (computed against Gaia's perfection) should improve with the post-jointcal fit.

      If 4 visits aren't enough, another possibility would be to reprocess twinkles with non-perfect refcats and then do the same comparison with the known-perfect refcat.

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            Parejkoj John Parejko created issue -
            Parejkoj John Parejko made changes -
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            Epic Link DM-8911 [ 29139 ]
            gcomoretto Gabriele Comoretto made changes -
            Remote Link This issue links to "Page (Confluence)" [ 24367 ]
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            swinbank John Swinbank added a comment -

            John Parejko — this ticket is several years old now, and we've done a bunch of testing on HSC. Is this still relevant?

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            swinbank John Swinbank added a comment - John Parejko — this ticket is several years old now, and we've done a bunch of testing on HSC. Is this still relevant?
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            Parejkoj John Parejko added a comment -

            Good question. I think this exploration might still be relevant for our future work on understanding what improvements may need to be made to jointcal. Can we leave it open until we've made some further decisions on that topic?

            Show
            Parejkoj John Parejko added a comment - Good question. I think this exploration might still be relevant for our future work on understanding what improvements may need to be made to jointcal. Can we leave it open until we've made some further decisions on that topic?

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              • Assignee:
                Parejkoj John Parejko
                Reporter:
                Parejkoj John Parejko
                Watchers:
                Colin Slater, John Parejko, John Swinbank, Simon Krughoff
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