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Discussion items


ItemWhoPre-Meeting NotesNotes and  Action Items
Project/Science Updates
Processing for weak lensing / DESC 

Discussion of processing needed to produce an Object catalog for DESC weak lensing studies. 

JB: Always intended to take a contribution from the community for shear estimation  - this is a presentation of a mature-state option. 

RHL: This work is optimal for weak shear but what about strong shear? We need to support all strong shear as well. Is metadetect good enough for them? Weak lensing looks at 1-2% added shear. 

ES: In the regime of say 10% shear or less metadetect is probably OK - for a 10% shear you get a 1% bias due to the fact that the shear is not in the linear regime.  Anything higher than that would require specialized code. In that case you have to go back and redo the processing and then the question become do you do the processing on cell-based coadds or some other dataset?

RHL: I think that a classic shape measurement on cell coadds will be fine

ES: All classic shape measurements will have this same limitation – if you go into the really strong lensing regime with the big arcs, specialized code is needed. 

MB: The DESC has people working in clustering thinking about this so they might be able to provide input. 

LPG: With cell-based coadds you remove images – this will impact the overall m5 coadded survey depth. Do you know how much? 

MB: Not as much as you think it would. Bob has numbers for this, 

AK: It's about a 5% loss, details depend on the size of the CCDs, how many satellite trails come through .. 

JB: No matter what coadd technique we use there will be some loss - there might be a slight tradeoff between SNR and systematics. 

SR: verified to what? and how many images were coadded?

MB: We verified to 10yr Rubin requirements, so better than 0.1% (at 3 sigma) in multiplicative bias and it works. So far only tested on a small number of images where small == 1-2. Warping all these images as well as running enough simulations with with all the shape noise and other sources of noise is very expensive.  We believe that the algorithms we have now will work  in the low number of images regime, which is where LSST will be in the first few years. 

MB: The PSFs are exact in the sense that there are no edges, this is important - we cannot recover shear without an exact PSF

CTS: You say you have a noise realization - but only one? 

ES: We can make 10 if we want and put them through the pipeline

CTS: 10 on the fly? Is that because it is not computationally prohibitive? Or make 10 and store them?

MB: We will probably store ~2 not 10 if we go this route

JB: Eventually want to use the same warps for these and other coadds

CTS: Time/space tradeoffs - we don't need precision for noise, can we use compression. This is done in DES to some level. 

JB: the six catalogs are narrow but have 5-6 times the number of rows. 

LPG: Do we need to serve them in Qserv? Can we use parquet, what are the access patterns for these catalogs. 

MBL: Do not need to do forced photometry back on the images. 

LPG: Do you plan to use cell-based coadds for the difference image templates

EB: Don't have good input data on that yet - a bit risky at this stage. 

  • Jim Bosch follow up with Strong Lensing people on the suitability of this work for strong lensing ( WL cluster people)   
  • Jim Bosch Understand the usage patterns  for the ShearObject catalogs   
  • Leanne Guy Schedule a follow up to this discussion to define conceptual schema for metadetect catalogs to add to DPDD  

Next meeting is:   

List of SST tasks (Confluence)

DescriptionDue dateAssigneeTask appears on
  • Robert Lupton Clarify the meaning of time in the object table. 1 sentence description in sdm_schemas, can link to a short DMTN.  Update 2022-02-09: Meeting to resolve this on 2022-02-21  
28 Feb 2022Robert Lupton2018-11-05 DM SST F2F Agenda and Meeting notes
  • Gregory Dubois-Felsmann check if SDM standardization is adequately represented in project documents, and whether DMTN-067 should be required.
31 Mar 2022Gregory Dubois-Felsmann2022-02-14 DM-SST Virtual F2F Agenda and Meeting notes
  • Steve Ritz Work with DM and Camera to develop plans for delivering a shutter position-vs-time model  
16 May 2022Steve Ritz2022-03-14 DM-SST Agenda and Meeting Notes
  • Gregory Dubois-Felsmann  / Leanne Guy Create a TN that outlines the science use cases and options for compressed PVIs from AP. Present the issue at DMLT VF2F and then the PST.   
13 Jun 2022Gregory Dubois-Felsmann2022-05-09 DM-SST Agenda and Meeting Notes
  • Eli Rykoff Report on what information DES used for their decision on using compression?  
25 Jul 2022Eli Rykoff2022-06-06 DM-SST VF2F Agenda and Meeting notes
  • Melissa Graham to draft a proposal for including pz in alert packets  
12 Sep 2022Melissa Graham2022-08-15 DM-SST Agenda and Meeting Notes
26 Sep 2022Steve Ritz2022-09-12 DM-SST Agenda and Meeting Notes
  • Gregory Dubois-Felsmann  start a technote to write down the details for science end user interface to SED corrections in catalogs  
31 Oct 2022Gregory Dubois-Felsmann2022-08-22 DM-SST Agenda and Meeting Notes
31 Dec 2022Leanne Guy2022-06-06 DM-SST VF2F Agenda and Meeting notes
28 Feb 2023Leanne Guy2023-01-23 DM-SST Agenda and Meeting Notes
  • Leanne Guy talk to Steve R about presenting plans for the ShearObject table to PST and SciCollab chairs   
20 Mar 2023Leanne Guy2023-02-27 DM-SST Agenda and Meeting Notes
31 Mar 2023Jim Bosch2023-02-27 DM-SST Agenda and Meeting Notes
  • Leanne Guy  talk to Gregory Dubois-Felsmann to review the original intent of the AFS-related Portal requirements before deciding on a course of action  
29 May 2023Leanne Guy2023-05-01 DM-SST Focus Meeting - Brokers in Commissioning
  • Leanne Guy Prepare to consult the PST on the question of providing compressed PVIs for AP outputs, to cover the period before the data become available in a DR.  
02 Jun 2023Leanne Guy2023-03-27 DM-SST Agenda and Meeting Notes
  • Jim Bosch Incorporate 30-60 day period for raws on disk into the strawman proposal and present to KT  
26 Jun 2023Jim Bosch2023-05-08 DM-SST Agenda and Meeting Notes
  • Parker Fagrelius Patrick Ingraham  how long will it take to do a scan as described? No need to scan the whole WL range but will require additional points outside nominal lambda range.  
30 Jun 2023Parker Fagrelius2023-03-27 DM-SST Agenda and Meeting Notes
31 Jul 2023Colin Slater2023-07-10 DM-SST Agenda and Meeting Notes
  • Eli Rykoff , Leanne Guy  Develop a proposal for what calibration processing, hardware, data we actually need and what will be needed for DR1. This has implications for the ORR and for prioritisation of work in commissioning  
31 Jul 2023Eli Rykoff2023-01-30 DM-SST Agenda and Meeting Notes
  • Yusra AlSayyad will look to see if there is any effort to help on option 1  
28 Aug 2023Yusra AlSayyad2023-08-14 DM-SST Agenda and Meeting Notes
  • Jim Bosch  Provide a physical example of that a  up on cell table would look like fo the Colin Slater / DAX team to review  
31 Aug 2023Jim Bosch2023-02-27 DM-SST Agenda and Meeting Notes