Striping issue in Y band Longslit data

[themiyan]

We have noticed a horizontal striping issue in the raw data in Y band. Unclear what caused this:

I wonder if this is some ghosting from the CSU configurations but the width is smaller than a CSU width.

When reduced I think this features are still contributing to the data (This is a lensed system, so there can be added confusion here on top of the striping issue on the raw data).

Any idea what is causing this? some example raw spectra + reduced attached. drew_lens_Y_eps.fits.zip

m201107_0055.fits.zip m201107_0056.fits.zip

m201107_0054.fits.zip

[csteidel]

Themiya- This looks to me like electronic noise of some kind - if you see the stripes in the reduced (i.e., differenced) data then it means the "pattern" is not stationary, which is common for such things. The low backgrounds in Y band make any features like this more noticeable. For how long do the features seem to persist (i,e., are they present throughout a one hour sequence of observations, or are they more transient?).

-Chuck

On Sun, Jan 3, 2021 at 11:54 PM Themiya Nanayakkara < notifications@github.com> wrote:

We have noticed a horizontal striping issue in the raw data in Y band. Unclear what caused this: [image: Screen Shot 2021-01-04 at 6 29 33 pm] https://user-images.githubusercontent.com/5274688/103512370-abea2880-4ebc-11eb-85c2-b91829a0ff2d.png

I wonder if this is some ghosting from the CSU configurations but the width is smaller than a CSU width.

When reduced I think this features are still contributing to the data (This is a lensed system, so there can be added confusion here on top of the striping issue on the raw data).

[image: Screen Shot 2021-01-04 at 6 38 25 pm] https://user-images.githubusercontent.com/5274688/103512569-0edbbf80-4ebd-11eb-8aae-0433ca1a300c.png

Any idea what is causing this? some example raw spectra + reduced attached. drew_lens_Y_eps.fits.zip https://github.com/Keck-DataReductionPipelines/MosfireDRP/files/5763583/drew_lens_Y_eps.fits.zip

m201107_0055.fits.zip https://github.com/Keck-DataReductionPipelines/MosfireDRP/files/5763579/m201107_0055.fits.zip m201107_0056.fits.zip https://github.com/Keck-DataReductionPipelines/MosfireDRP/files/5763580/m201107_0056.fits.zip

m201107_0054.fits.zip https://github.com/Keck-DataReductionPipelines/MosfireDRP/files/5763576/m201107_0054.fits.zip

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[themiyan]

Hi Chuck, We only did 8 exposures since this was a lens target from Drew. This is clearly seen in all the 4 pairs of A-B as seen in the image below, so as you mention then it could be some electronic noise in the detectors. We had other bands that night and did not see them there.

[joshwalawender]

@themiyan Have you checked to see if this is visible in other images from the same night? If it is confined to a single target, then that would be a clue as to the origin. If it is visible in individual frames from other targets before or after this one, that would suggest something electronic.

[themiyan]

@joshwalawender this is not just on one source. What we found from our Jan runs is that if there are sufficient frames, these patterns are removed by the DRP. Ivo performed some tests and found that "Pattern noise in Y is a ~10% rms effect over approx half the detector ".