DM-45302: ISR section #10
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czwa
approved these changes
Nov 21, 2024
| \subsection{ISR package} | ||
| \label{sec:ip_isr} | ||
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| Exposures from LSST cameras are affected by instrumental effects, ranging from well-known CCD effects like dark currents or biases to effects more recently characterized like tree-rings (see \cite{park_properties_2017,park_tree_2020,esteves_photometry_2023} for more details on tree rings in LSSTCam) or the Brighter-Fatter effect as discussed in \cite{broughton_2023}. Correcting for these effects requires specific calibrations, which we refer to as calibration products. In LSST cameras, calibration products typically are a combined bias, a combined dark, a Photon Transfer Curve (PTC), a crosstalk matrix, a list of defects and a look-up table of non-linearity parameters. |
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| The \texttt{ip\_isr} package\footnote{\url{https://github.com/lsst/ip_isr}} contains the codes needed to remove instrument signatures in exposures from LSST cameras and to produce calibration products. | ||
| To inform our ISR approach, we first designed a model of the instrument, displayed in Fig. \ref{fig:isr_model}, based on our knowledge of the hardware and electronics. This model states the order in which the different known instrumental effects happen, from a photon hitting the CCD to the output ADC unit (ADU) signal. | ||
| In turn, \texttt{isrTaskLSST} in \texttt{ip\_isr} sequentially applies correction of these effects, typically by calling other \texttt{Tasks} (\textit{e.g.} overscan, crosstalk, etc.) also implemented in \texttt{ip\_isr}. |
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"These corrections are applied in the opposite order as their effects occur in the model, as we are attempting to remove the impact of those effects on the image."? I mostly want to qualify that sequentially operates in the opposite direction as how they're added in the model.
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| Overall, \texttt{isrTaskLSST} takes a \texttt{raw} CCD exposure, and calibration products if available, and outputs a \texttt{Struct} containing the input exposure, the \texttt{postISRCCD} output exposure as well as its binned version for easier display, the exposure before interpolation and statistics on the output exposure. |
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"containing the output exposure"? The input isn't returned.
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And possibly "exposure without interpolation," as it should have all the other processing steps done.
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| Overall, \texttt{isrTaskLSST} takes a \texttt{raw} CCD exposure, and calibration products if available, and outputs a \texttt{Struct} containing the input exposure, the \texttt{postISRCCD} output exposure as well as its binned version for easier display, the exposure before interpolation and statistics on the output exposure. | ||
| \texttt{IsrTaskLSSTConfig} defines the configurations used in this \texttt{Task}, they are set by default to their expected value to perform ISR on a typical LSSTCam exposure. Configurations starting with \texttt{do} will typically correspond to an ISR step, they are turned on or off in the pipelines when producing the different calibration products. |
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"Configuration parameters starting with [...]"
| The pipelines to build calibration products (\texttt{cp}) for the LSST cameras are defined in \texttt{cp\_pipe}\footnote{\url{https://github.com/lsst/cp\_pipe} and see documentation at \url{https://pipelines.lsst.io/modules/lsst.cp.pipe/constructing-calibrations.html}}. | ||
| They mainly set \texttt{isrTaskLSST} configurations needed for each calibration product. In some cases, they also specify whether to combine exposures (for bias or dark exposures for instance) and to bin exposures to support display. | ||
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Can you add a a sentence or two that the configurations for construction enable all corrections that happen in IsrTask up to but not including the application of the correction to be generated, and that the verify configuration enables everything up to and including the application of the correction being verified? It may be obvious, but I don't think it hurts to be clear.
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