Example notebooks and supporting python code for reducing MIRI Imaging observations. Extensively tested on MIRI Commissioning and Early Release Observations (EROs). Uses the official jwst pipeline.
Presentation given to the MIRI Imaging Team 20 June 2022.
Extra steps were done to enhance the data.
1. After the Detector1 processing, the rate file was recreated from the rateints file to correct a bug. This bug affects the reported rate value in regions that saturate in after the 3rd group. This bug will be fixed in a future version of the official jwst pipeline.
2. The astrometry (WCS, pointing) between mosaics tiles is updated based on an analysis of the "tweakreg" results in the Image3 stage of the pipeline. Experience shows that the relative astrometry between dithers using the same guide star is quite good, but there can be significant (up to 2 arcsec) updates needed between mosaic tiles where different guide stars are used. The analysis results from the shortest wavelength filter are used for all filters. This is done as often there are not enough sources at longer wavelengths to provide a good update to the astrometry.
3. In the case of sufficiently sparse fields, a sky/background image can be created and subtracted from all the images. This sky image is created by sigma clipping all the images aligned in instrument coordinates. This can and does inject residual small scale variations in the background. This step was done for the SMACS 0723 and Stephan's Qunitet EROs and the LMC Flat region.
Portion of the LMC astrometric field used as part of creating the Imaging flat fields. A five mosaic tile observation with multiple dithers in each tile. All 9 Imaging filters observed.
Notebooks:
- LMCFlat_F560W: Reduction of F560W data.
- LMCFlat_F560W_skysub: Creation and subtraction of a sky/background image.
- LMCFlat_F770W: Reduction of F770W data. Note that the updates to the astronomery used the results from the F560W tweakreg analysis.
- LMCFlat_F770W_skysub: Creation and subtraction of a sky/background image.
- Analyze_teakreg_shifts: Analyzes the results of the 1st run of LMCFlat_F560W to determine the astrometric offsets to apply for all of the filters for the different mosaic tiles.
Early Release Observation. Example showing the very experimental column/row pull up/down correction.
- StephanQuintet_F1000W_clean: Mainly cosmetic very experimental col/row pull/up/down cleaning on the F1000W images.
This notebook shows a science workflow of taking uncal images from the pipeline, running them through both level 1 (calwebb_detector1) and 2 (calwebb_image2) pipelines, then creating a median background (sky) image and subtracting that from the calibrated images and combining the sky subtracted data into a mosaic. The data used is from the SMACS program (PID 2736). This sky creation and subtraction routine works best on data without large extended sources such as galaxies and nebulae.
Karl Gordon Misty Cracraft
This code is licensed under a 3-clause BSD style license (see the
LICENSE file).