soxs_mdark¶

Every raw CCD image contains counts resulting from a ‘dark current’, electrons released due to the thermal effects in the CCD material. For both the UVB-VIS (< 0.00012 \(\rm{e^{-}/s/pixel}\)) and NIR detectors (< 0.005 \(\rm{e^{-}/s/pixel}\)), the dark current is almost negligible. Not all pixels will have the same dark current, with some pixels having a higher-than-typical current. These are so-called ‘hot-pixels’, and these must be identified and recorded (using the create_noise_map utility).

The purpose of the soxs_mdark recipe is to generate a master-dark frame used to remove flux attributed to the dark current from other frames.

Usage¶

The soxs_mdark recipe can be run with the following convention:

soxspipe [-Vx] mdark <inputFrames> [-o <outputDirectory> -s <pathToSettingsFile>]

To rerun a previously executed soxs_mdark recipe, you can find the execution command at the end of the recipe log file (found in the workspace products/soxs_mdark directory). Use the -x flag to overwrite the product files if they already exist. For example, from the root of your workspace, you would run a command like:

soxspipe mdark sof/20260111T082924_NIR_3_MDARK_5_0S_SOXS.sof -s ./sessions/base/soxspipe.yaml  -x

To adjust the default settings for the soxs_mdark recipe, open the soxspipe.yaml file referenced in the command above in a text editor, navigate to the soxs_mdark dictionary, save the file and rerun the recipe command. The settings’ descriptions can be found in Table 5.

Product files are written in the products/soxs_mdark, and QC plots are in the qc/soxs_mdark workspace directory. A report of the product files, QC plots and metrics is also printed to the terminal. The QC metrics calculated for soxs_mdark are found in Table 8.

Reduction Tips¶

As with soxs_mbias, the soxs_mdark recipe is one of the simpler recipes, and therefore, it is typically very robust against failures. To reduce the time it takes to run the recipe (at the expense of allowing a few more outlying pixels into your master bias frame), you can experiment with reducing both frame-clipping-iterations and stacked-clipping-iterations (although speed gains will be very moderate).

Parameters¶

Table 5 The `soxs_mdark` recipe parameters.¶
Parameter	Description	Type	Entry Point	Related Util
`frame_clipping_sigma`	number of \(\sigma\) from the median frame flux beyond which pixel is added to the bad-pixel mask	float	settings file	`clip_and_stack`
`frame_clipping_iterations`	number of \(\sigma\)-clipping iterations to perform when adding pixels to the bad-pixel mask	int	settings file	`clip_and_stack`
`stacked_clipping_sigma`	number of \(\sigma\) deviations from the median pixel flux beyond which pixel is excluded from stack	float	settings file	`clip_and_stack`
`stacked_clipping_iterations`	number of \(\sigma\)-clipping iterations to perform before stacking	int	settings file	`clip_and_stack`

Input¶

Table 6 Input files for the `soxs_mdark` recipe. The files are typically passed to the `soxs_mdark` recipe via a set-of-file (sof) file listing one file per line.¶
Data Type	Content	Related OB	Min. Frame Count
FITS images	raw dark frames (exposures with identical exposure time and detectors readout parameters).	`SOXS_gen_cal_VISDark`, `SOXS_gen_cal_NIRDark`, `SOXS_img_cal_Dark`	3

Output¶

Table 7 Output files for the `soxs_mdark` recipe and their respective ESO PRO keywords.¶
Label	Content	Data Type	PRO CATG	PRO TYPE	PRO TECH
`MDARK`	Master dark frame (frame containing typical dark-current flux accumulated over the exposure time of the input frames)	FITS image	`DARK_<ARM>`	`REDUCED`	`IMAGE`

QC Metrics¶

Table 8 Quality Control metrics calculated in the `soxs_mdark` recipe.¶
Label	Description	Unit	Acceptable Range
`HOTPIX FRAC`	Fraction of hot pixels	-	-
`MDARK MEDIAN`	Median flux level of master dark	electrons	NIR: [-15, 50]
`HOTPIX NUM`	Number of hot pixels	-	-
`RAW RON`	RON in single DARK	electrons	NIR: [0,30]