Synthetic source injection on multiple visits

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#1

Hi, I had been working on something along the lines demonstrated in the DP02_14_Injecting_Synthetic_Sources.ipynb tutorial, but applied for strong Lensing purposes, however, I have a few questions/issues that I hope I can get some help with.

  1. From the tutorial point of view, i.e. from the Jupyter notebook, is it possible to write the injected exposures back to a butler so that further analysis on the injected visits can be done?

  2. About the injection of the same synthetic image into different visits to coadd them afterwards, my impression is that the notebook tutorial would already take into account for the correct rotation of the injected image, this is specially important if its an extended image, like a simulated lens. But to verify this I would like to coadd the images, so it takes me back to point 1. Is there another way I could check the alignment is correct?

  3. Furthermore, I’ve tried to inject the same synthetic image, a lens, to several visits from the command line using the pipeline tasks, and I get the injection right but the wrong alignment. I haven’t found a way to tell the injection task how to align the image to a given visit. This is the command line I’ve used to produce the two images below, as you can see in both I get exactly the same orientation of the injected lens, therefore, if I coadd them I’ll get all the injected visits with the image injected in the exact same position.

An additional issue I just faced when trying to produce a fresh example is that the command I used to run seems not to be working, no injected image is saved, but I don’t see any error in the log. I’ll try again later to see if I can figure out what happen.

This is the command I have run in the past

pipetask --long-log --log-file inject.log run --register-dataset-types -b dp02 -i 2.2i/runs/DP0.2,u/alxogm/inject_SL_t0 -o /runs/DP0.2,u/alxogm/inject_SL -p /home/alxogm/WORK/source_injection/pipelines/inject_visit.yaml -d "instrument='LSSTCam-imSim' AND skymap='DC2' AND visit=656444 AND detector=38 AND band='r' "

This is following documentation in https://pipelines.lsst.io/v/daily/modules/lsst.source.injection/reference/21_inject_synthetic_sources.html#injecting-postage-stamps
Thanks for your help.

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#2

Just wanted to let you know that a demo is being prepared, but in the meantime, anyone else can join the conversation!
Thanks!

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#3

Hi @ChristinaAdair is there a repository where I can see a preliminary version or in development of this demos? Thanks!

#4

Hello! I think we will have more information on this soon. I am not sure if there is a repository, but I will ask.

#5

Hi @alxogm,

I can provide a partial answer for your first question, about how to write the injected exposure back to the butler.

Follow DP0.2 tutorial notebook 14 on synthetic source injection up to and including Section 4.3.2. Then use the writeable_butler to put the injected_exposure into the butler, using the line below. In this case I’ve used the INJECTION_CATALOG_COLLECTION defined in the tutorial for the run name.

writeable_butler.put(injected_exposure, 'calexp', dataId=dataId_g, run=INJECTION_CATALOG_COLLECTION)

Then instantiate a new temporary butler (tempButler) that points to the collection where the injected exposure was put. Retrieve it and plot it to prove to yourself it is your image with the sources injected.

tempButler = Butler(butler_repo, collections=[INJECTION_CATALOG_COLLECTION])
my_calexp = tempButler.get('calexp', dataId_g)
fig = plt.figure()
display = afwDisplay.Display(frame=fig)
display.scale('asinh', 'zscale')
display.mtv(my_calexp.image)
plt.show()
del tempButler

Caveats
Although this is a way to write to the butler, I am not sure that this is a path to being able to coadd. In DP0.2 tutorial notebook 9a, it is explained how coadding DP0.2 images has to be done with an older version of the pipelines, because the pipelines have evolved substantially since DP0.2 was processed two years ago. The source injection functionality was only added recently. So at the moment, I don’t think there is a way to make an injection pipeline that can both inject sources into, and then coadd, DP0.2 images. But this is not the final word! We will keep investigating and report back, on this and about your other reported issues.

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#6

Hi Alma - Unfortunately, Melissa’s point in the “Caveats” above is correct. The tools in the pipelines to coadd images currently don’t work with the DP0.2 data products. Thus, even if you are able to write the injected images to a Butler, you cannot use (to my knowledge) the pipelines tools to coadd them. We are exploring whether there are other ways to create coadds from the images, but it may take a while.

Regarding the other part of your question (aligning the images) – if you supply a value for “beta” (the position angle for the injected source) in the injection catalog, the images should be aligned correctly. However, because calexp images have different orientations, you will want to “register” (or “warp”) them so that they are oriented in the same direction. There is a notebook in this DP0.2 repo called “aligning_injected_images.ipynb” that shows how to do this. (That notebook also does a simple “sum” of the resulting images at the end, which is definitely not the scientifically best way to combine the images. It’s just an illustration that they are aligned.)

Hope this is helpful!

#7

Also, regarding writing injected images back to the Butler – @lskelvin added a new section to the FAQ for the source_injection package that explains how to do this. See this link for details.

#8

Thanks @MelissaGraham and @jeffcarlin , yes I am aware of the caveats, but it’s ok for now. I will try your recommendations and see if I can achieve my goal.

Best,
Alma