AssembleCoaddTask#

class lsst.drp.tasks.assemble_coadd.AssembleCoaddTask(*args, **kwargs)#

Bases: CoaddBaseTask, PipelineTask

Assemble a coadded image from a set of warps.

Each Warp that goes into a coadd will have its flux calibrated to nJy. WarpType may be one of ‘direct’ or ‘psfMatched’, and the boolean configs config.makeDirect and config.makePsfMatched set which of the warp types will be coadded. The coadd is computed as a mean with optional outlier rejection. Criteria for outlier rejection are set in AssembleCoaddConfig. Finally, Warps can have bad ‘NaN’ pixels which received no input from the source calExps. We interpolate over these bad (NaN) pixels.

AssembleCoaddTask uses several sub-tasks. These are

ScaleZeroPointTask
create and use an imageScaler object to scale the photometric zeropoint for each Warp (deprecated and will be removed in DM-49083).
InterpImageTask
interpolate across bad pixels (NaN) in the final coadd

You can retarget these subtasks if you wish.

Raises#

RuntimeError: Raised if unable to define mask plane for bright objects.

Notes#

Debugging: AssembleCoaddTask has no debug variables of its own. Some of the subtasks may support lsstDebug variables. See the documentation for the subtasks for further information.

Methods Summary

`applyAltMaskPlanes`(mask, altMaskSpans)	Apply in place alt mask formatted as SpanSets to a mask.
`assembleMetadata`(coaddExposure, warpRefList, ...)	Set the metadata for the coadd.
`assembleOnlineMeanCoadd`(coaddExposure, ...)	Assemble the coadd using the "online" method.
`assembleSubregion`(coaddExposure, bbox, ...)	Assemble the coadd for a sub-region.
`filterWarps`(inputs, goodVisits)	Return list of only inputRefs with visitId in goodVisits ordered by goodVisit.
`prepareInputs`(refList, coadd_bbox[, ...])	Prepare the input warps for coaddition by measuring the weight for each warp.
`prepareStats`([mask])	Prepare the statistics for coadding images.
`processResults`(coaddExposure[, ...])	Interpolate over missing data and mask bright stars.
`run`(skyInfo, *, warpRefList, ...[, ...])	Assemble a coadd from input warps.
`runQuantum`(butlerQC, inputRefs, outputRefs)	Do butler IO and transform to provide in memory objects for tasks `run` method.
`setBrightObjectMasks`(exposure, brightObjectMasks)	Set the bright object masks.
`setInexactPsf`(mask)	Set INEXACT_PSF mask plane.

Methods Documentation

applyAltMaskPlanes(mask, altMaskSpans)#

Apply in place alt mask formatted as SpanSets to a mask.

Parameters#

masklsst.afw.image.Mask: Original mask.
altMaskSpansdict: SpanSet lists to apply. Each element contains the new mask plane name (e.g. “CLIPPED and/or “NO_DATA”) as the key, and list of SpanSets to apply to the mask.

Returns#

masklsst.afw.image.Mask: Updated mask.

assembleMetadata(coaddExposure, warpRefList, weightList, psfMatchedWarpRefList=None)#

Set the metadata for the coadd.

This basic implementation sets the filter from the first input.

Parameters#

coaddExposurelsst.afw.image.Exposure: The target exposure for the coadd.
warpRefListlist: List of dataset handles (data references) to warp.
weightListlist: List of weights.
psfMatchedWarpRefListlist | None, optional: List of dataset handles (data references) to psfMatchedWarps.

Raises#

AssertionError: Raised if there is a length mismatch.

assembleOnlineMeanCoadd(coaddExposure, warpRefList, imageScalerList, weightList, altMaskList, statsCtrl, nImage=None)#

Assemble the coadd using the “online” method.

This method takes a running sum of images and weights to save memory. It only works for MEAN statistics.

Parameters#

coaddExposurelsst.afw.image.Exposure: The target exposure for the coadd.
warpRefListlist: List of dataset handles (data references) to warp.
imageScalerListlist: List of image scalers. Deprecated and will be removed after v29 in DM-49083.
weightListlist: List of weights.
altMaskListlist: List of alternate masks to use rather than those stored with warp, or None. Each element is dict with keys = mask plane name to which to add the spans.
statsCtrllsst.afw.math.StatisticsControl: Statistics control object for coadd.
nImagelsst.afw.image.ImageU, optional: Keeps track of exposure count for each pixel.

assembleSubregion(coaddExposure, bbox, warpRefList, imageScalerList, weightList, altMaskList, statsFlags, statsCtrl, nImage=None)#

Assemble the coadd for a sub-region.

For each coaddTempExp, check for (and swap in) an alternative mask if one is passed. Remove mask planes listed in config.removeMaskPlanes. Finally, stack the actual exposures using lsst.afw.math.statisticsStack with the statistic specified by statsFlags. Typically, the statsFlag will be one of lsst.afw.math.MEAN for a mean-stack or lsst.afw.math.MEANCLIP for outlier rejection using an N-sigma clipped mean where N and iterations are specified by statsCtrl. Assign the stacked subregion back to the coadd.

Parameters#

coaddExposurelsst.afw.image.Exposure: The target exposure for the coadd.
bboxlsst.geom.Box: Sub-region to coadd.
warpRefListlist: List of dataset handles (data references) to warp.
imageScalerListlist: List of image scalers. Deprecated and will be removed after v29 in DM-49083.
weightListlist: List of weights.
altMaskListlist: List of alternate masks to use rather than those stored with warp, or None. Each element is dict with keys = mask plane name to which to add the spans.
statsFlagslsst.afw.math.Property: Property object for statistic for coadd.
statsCtrllsst.afw.math.StatisticsControl: Statistics control object for coadd.
nImagelsst.afw.image.ImageU, optional: Keeps track of exposure count for each pixel.

filterWarps(inputs, goodVisits)#

Return list of only inputRefs with visitId in goodVisits ordered by goodVisit.

Parameters#

inputslist of DeferredDatasetRef: List of lsst.pipe.base.connections.DeferredDatasetRef with dataId containing visit.
goodVisitdict: Dictionary with good visitIds as the keys. Value ignored.

Returns#

filterInputslist [lsst.pipe.base.connections.DeferredDatasetRef]: Filtered and sorted list of inputRefs with visitId in goodVisits ordered by goodVisit.

prepareInputs(refList, coadd_bbox, psfMatchedWarpRefList=None)#

Prepare the input warps for coaddition by measuring the weight for each warp.

Before coadding these Warps together compute the weight for each Warp.

Parameters#

refListlist: List of dataset handles (data references) to warp.
psfMatchedWarpRefListlist | None, optional: List of dataset handles (data references) to psfMatchedWarp.

Returns#

resultStruct

Results as a struct with attributes:

warpRefList: list of dataset handles (data references) to warp.
weightList: list of weightings.
imageScalerList: list of image scalers. Deprecated and will be removed in DM-49083.

prepareStats(mask=None)#

Prepare the statistics for coadding images.

Parameters#

maskint, optional: Bit mask value to exclude from coaddition.

Returns#

statsStruct

Statistics as a struct with attributes:

statsCtrl: Statistics control object for coadd (StatisticsControl).
statsFlags: Statistic for coadd (Property).

processResults(coaddExposure, brightObjectMasks=None, dataId=None)#

Interpolate over missing data and mask bright stars.

Parameters#

coaddExposurelsst.afw.image.Exposure: The coadded exposure to process.
brightObjectMaskslsst.afw.table or None, optional: Table of bright objects to mask.
dataIdlsst.daf.butler.DataId or None, optional: Data identification.

run(skyInfo, *, warpRefList, imageScalerList, weightList, psfMatchedWarpRefList=None, altMaskList=None, mask=None, supplementaryData=None)#

Assemble a coadd from input warps.

Assemble the coadd using the provided list of coaddTempExps. Since the full coadd covers a patch (a large area), the assembly is performed over small areas on the image at a time in order to conserve memory usage. Iterate over subregions within the outer bbox of the patch using assembleSubregion to stack the corresponding subregions from the coaddTempExps with the statistic specified. Set the edge bits the coadd mask based on the weight map.

Parameters#

skyInfoStruct: Struct with geometric information about the patch.
warpRefListlist: List of dataset handles (data references) to Warps (previously called CoaddTempExps).
imageScalerListlist: List of image scalers. Deprecated and will be removed after v29 in DM-49083.
weightListlist: List of weights.
psfMatchedWarpRefListlist, optional: List of dataset handles (data references) to psfMatchedWarps.
altMaskListlist, optional: List of alternate masks to use rather than those stored with warp.
maskint, optional: Bit mask value to exclude from coaddition.
supplementaryDataStruct, optional: Struct with additional data products needed to assemble coadd. Only used by subclasses that implement _makeSupplementaryData and override run.

Returns#

resultStruct

Results as a struct with attributes:

coaddExposure: Coadded exposure (Exposure).
nImage: Exposure count image (Image), if requested.
inputMap: Bit-wise map of inputs, if requested.
warpRefList: Input list of dataset handles (data refs) to the warps (DeferredDatasetHandle) (unmodified).
imageScalerList: Input list of image scalers (list) (unmodified). Deprecated and will be removed after v29 in DM-49083.
weightList: Input list of weights (list) (unmodified).

Raises#

lsst.pipe.base.NoWorkFound: Raised if no dataset handles (data references) are provided.

runQuantum(butlerQC, inputRefs, outputRefs)#

Do butler IO and transform to provide in memory objects for tasks run method.

Parameters#

butlerQCQuantumContext: A butler which is specialized to operate in the context of a lsst.daf.butler.Quantum.
inputRefsInputQuantizedConnection: Datastructure whose attribute names are the names that identify connections defined in corresponding PipelineTaskConnections class. The values of these attributes are the lsst.daf.butler.DatasetRef objects associated with the defined input/prerequisite connections.
outputRefsOutputQuantizedConnection: Datastructure whose attribute names are the names that identify connections defined in corresponding PipelineTaskConnections class. The values of these attributes are the lsst.daf.butler.DatasetRef objects associated with the defined output connections.

setBrightObjectMasks(exposure, brightObjectMasks, dataId=None)#

Set the bright object masks.

Parameters#

exposurelsst.afw.image.Exposure: Exposure under consideration.
brightObjectMaskslsst.afw.table: Table of bright objects to mask.
dataIdlsst.daf.butler.DataId, optional: Data identifier dict for patch.

setInexactPsf(mask)#

Set INEXACT_PSF mask plane.

If any of the input images isn’t represented in the coadd (due to clipped pixels or chip gaps), the CoaddPsf will be inexact. Flag these pixels.

Parameters#

masklsst.afw.image.Mask: Coadded exposure’s mask, modified in-place.