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  1. Data Management
  2. DM-6565

Replace short-period coadds with coadd difference images

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    • Team:
      Data Release Production

      Description

      Instead of producing short-period (e.g. yearly) coadds for the purpose of detecting and characterizing faint, slowly-changing sources, I believe we should diff these coadds against a full-depth coadd (or perhaps each other), and detect and characterize on the difference images.

      This should reduce blending issues in characterizing these objects, and it should make what I'm calling the DeepAssociate pipeline (where we merge Footprints and Peaks to define Object candidates, just before deblending) much easier, because the short-period coadds will no longer contribute redundant detections for static sources at single-year depth.

      I thus far have not included this proposal in LDM-151, in order to maintain consistency with the DPDD.

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          tjenness Tim Jenness added a comment -

          I've updated DMS-REQ-0337 to read:

          Specification: The DMS shall be able to detect faint objects showing long-term variability, or nearby object with high proper motions.

          Discussion: For example, this could be implemented using short-period (yearly) coadds.

          DPDD will need quite a lot more editing to stop it saying that we are creating short-period coadds. I'm not sure how vague we are allowed to be in a document that is explicitly defining the data products (albeit ones that are never retained, so in some sense, it's weird we are telling people about products they aren't getting).

          Show
          tjenness Tim Jenness added a comment - I've updated DMS-REQ-0337 to read: Specification: The DMS shall be able to detect faint objects showing long-term variability, or nearby object with high proper motions. Discussion: For example, this could be implemented using short-period (yearly) coadds. DPDD will need quite a lot more editing to stop it saying that we are creating short-period coadds. I'm not sure how vague we are allowed to be in a document that is explicitly defining the data products (albeit ones that are never retained, so in some sense, it's weird we are telling people about products they aren't getting).
          Hide
          jbosch Jim Bosch added a comment -

          Given that we'll actually produce short-period coadds in the course of making short-period difference images, I think the text in the DPDD is probably safe.

          That said, I definitely agree that it's weird that we define a lot of coadd data products and then state that they aren't really going to be available.

          Show
          jbosch Jim Bosch added a comment - Given that we'll actually produce short-period coadds in the course of making short-period difference images, I think the text in the DPDD is probably safe. That said, I definitely agree that it's weird that we define a lot of coadd data products and then state that they aren't really going to be available.
          Hide
          tjenness Tim Jenness added a comment -

          The initial ticket asked for changes in DPDD, but all I've done is tweaked a requirement. What changes do you need to be made to DPDD to allow you the flexibility you need in LDM-151?

          Show
          tjenness Tim Jenness added a comment - The initial ticket asked for changes in DPDD, but all I've done is tweaked a requirement. What changes do you need to be made to DPDD to allow you the flexibility you need in LDM-151?
          Hide
          jbosch Jim Bosch added a comment -

          I think my past self (who opened the ticket) didn't realize that the DPDD was already consistent with what I'd like to do. I think we can just close this, and I'll open a new issue to get it into LDM-151.

          Show
          jbosch Jim Bosch added a comment - I think my past self (who opened the ticket) didn't realize that the DPDD was already consistent with what I'd like to do. I think we can just close this, and I'll open a new issue to get it into LDM-151.
          Hide
          tjenness Tim Jenness added a comment -

          Closing as a new requirement has been created and it has been decided that DPDD is mostly compliant with current thinking.

          Show
          tjenness Tim Jenness added a comment - Closing as a new requirement has been created and it has been decided that DPDD is mostly compliant with current thinking.

            People

            • Assignee:
              jbosch Jim Bosch
              Reporter:
              jbosch Jim Bosch
              Watchers:
              Jim Bosch, John Swinbank, Robert Lupton, Tim Jenness, Zeljko Ivezic
            • Votes:
              0 Vote for this issue
              Watchers:
              5 Start watching this issue

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                Updated:
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