Webb Office Hours Session 49: April 9, 2026
Q&A's:
Q1: Where are the Webb Office Hours procedures and guidelines?
A1: Webb Office Hours. Type your question into the WebEx chat. We will asynchronously copy questions from the chat to this main page and work through them as a group. If you have images to share please give WebEx permission to share your screen (you may need to log out and log back in again to enable this feature.)
Q2: I have NIRSpec IFU data and am seeing light and dark stripes along one spatial dimension in our mosaics. Is there a way we can reduce these stripes? Is there a better way to apply clean-flicker noise?
A2: It can be difficult to remove the noise and depends on the astronomical scene, and requires custom masking to mask out the science source. It helps to look at the 2D rate images to see how well the clean-flicker noise is doing. The map between IFU slices and traces is shown in JDox here: https://jwst-docs.stsci.edu/jwst-near-infrared-spectrograph/nirspec-observing-modes/nirspec-ifu-spectroscopy#gsc.tab=0
- A recommended starting point for 1/f (flicker) noise correction would be to use the following parameters in clean_flicker_noise. Improvement can be seen by applying clean_flicker_noise in stage1 and stage2 (i.e., on both ramp and rate files), and we would recommend starting with the parameters below for both stages:
- mask_science_region=True
- n_sigma=1.5
- fit_method=median
- background_method=None
- In some cases fit_method = fft can provide improvements in the 1/f cleaning
- User's are encouraged to compare cleaned vs uncleaned rate images to evaluate how well 1/f noise (vertical striping on NIRSpec detectors) is being cleaned
In terms of mapping stripes seen in IFU slices to detector positions, users can build IFU aligned cubes (setting the cube_build parameter coord_system = ifualign ) where the cube is oriented such that the x-axis of the cube is along the cross-dispersion of the slices, and the y-axis steps across slices, which may be helpful for mapping stripes along the cube to their detector positions.
Q3: I also have MIRI MRS data with similar noise issues. What can be done here?
A3: You should try using the similar strategies as detailed above for NIRSpec. If you have additional problems, please submit a Help Desk ticket and an expert will be able to help you.
https://jwst-pipeline.readthedocs.io/en/stable/jwst/clean_flicker_noise/main.html
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