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  1. Request For Comments
  2. RFC-617

Update HSC's focal plane camera geometry to use units of millimeters

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      The obs_subaru camera geometry currently uses an effective focal plane scaling of "unity" (i.e. plateScale = 1 arcsec/mm, pixelSize = 1 mm). All other LSST camera geometries are defined in actual physical units: millimeters on the focal plane. For the work being done in DM-19943 (and see RFC-616), we need to have the correct CCD plate scale in the camera geometry to properly reflect the pixel-to-focal plane conversion.

      In addition to this unit conversion being a good idea in its own right, the investigations in DM-19943 rendered us fairly confident that there is an inconsistency in the current HSC cameraGeom itself that was actually responsible for most of the problems. Updating the units thus has the added bonus of eliminating the inconsistency without us having to debug it further. Furthermore, HSC's non-conventional unit system has caused mild headaches for a few developers (e.g. erykoff's calibration work on fgcmcal), so the switch will benefit them as well.

      There are a few package affected and will require accommodation. These have already been exposed and tested on DM-20289 for singleFrame and skyCorrection and, in the context of ci_hsc, through coaddition and multiband with the cursory tests there (but without running jointcal, which is not yet included in any of our CI scripts). A more rigorous battle testing is being performed on DM-20548 (the ticket triggered by this RFC) which will include a full run of at least one tract from the RC2 dataset (i.e. running through singleFrameDriver, skyCorrection, jointcal, coaddDriver, and multibandDriver) to make sure the results are consistent with that of the latest weekly reprocessing run.

      One item of note: this change will effectively break meas_mosaic. While updating it to accommodate the unit update is not completely out of the question, it would take significant effort which does not seem worthwhile given the adoption of jointcal as our “uber calibration” algorithm. As such, this RFC is also effectively proposing the official retirement of meas_mosaic.

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            erykoff Eli Rykoff added a comment -

            That is a very good point! I wonder how the implementation passed Jenkins? I guess this wasn't tested within meas_mosaic. In any event, I think that should happen!

            erykoff Eli Rykoff added a comment - That is a very good point! I wonder how the implementation passed Jenkins? I guess this wasn't tested within meas_mosaic . In any event, I think that should happen!

            I was just typing a note to ask about this (I was going to write a community post warning that, while it compiles, it would produce garbage, if anything, so should not be used).  I'm not sure of the official deprecation process for a repository.  Should this RFC be moved back to the "Approved" stage while I await instructions on how to do the official deprecation of meas_mosaic?

            lauren Lauren MacArthur added a comment - I was just typing a note to ask about this (I was going to write a community post warning that, while it compiles, it would produce garbage, if anything, so should not be used).  I'm not sure of the official deprecation process for a repository.  Should this RFC be moved back to the "Approved" stage while I await instructions on how to do the official deprecation of meas_mosaic ?

            meas_mosaic got a minimal update such that the tests pass, so Jenkins was indeed happy.

            lauren Lauren MacArthur added a comment - meas_mosaic got a minimal update such that the tests pass, so Jenkins was indeed happy.

            swinbank has graciously offered to take on the deprecation of meas_mosaic on DM-21053.

            lauren Lauren MacArthur added a comment - swinbank has graciously offered to take on the deprecation of meas_mosaic on DM-21053 .

            Apparently I don't have permission to set this RFC back to “adopted”. However, I agree with the premise that this RFC should not be regarded as complete until meas_mosaic has been dropped from lsst_distrib (not just deprecated, but removed). I'll take care of that on DM-21053.

            swinbank John Swinbank added a comment - Apparently I don't have permission to set this RFC back to “adopted”. However, I agree with the premise that this RFC should not be regarded as complete until meas_mosaic has been dropped from lsst_distrib (not just deprecated, but removed). I'll take care of that on DM-21053 .

            People

              lauren Lauren MacArthur
              lauren Lauren MacArthur
              Chris Morrison, Eli Rykoff, Gabriele Comoretto [X] (Inactive), Jim Bosch, John Parejko, John Swinbank, Joshua Meyers, Lauren MacArthur, Paul Price, Robert Lupton, Tim Jenness, Wil O'Mullane, Yusra AlSayyad
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