DipoleFitPlugin

class lsst.ip.diffim.DipoleFitPlugin(config, name, schema, metadata)

Bases: lsst.meas.base.SingleFramePlugin

A single frame measurement plugin that fits dipoles to all merged (two-peak) diaSources.

This measurement plugin accepts up to three input images in its measure method. If these are provided, it includes data from the pre-subtraction posImage (science image) and optionally negImage (template image) to constrain the fit. The meat of the fitting routines are in the class DipoleFitAlgorithm.

Notes

The motivation behind this plugin and the necessity for including more than one exposure are documented in DMTN-007 (http://dmtn-007.lsst.io).

This class is named ip_diffim_DipoleFit so that it may be used alongside the existing ip_diffim_DipoleMeasurement classes until such a time as those are deemed to be replaceable by this.

Attributes Summary

APCORR_ORDER
CENTROID_ORDER
DEFAULT_CATALOGCALCULATION
FAILURE_EDGE
FAILURE_FIT
FAILURE_NOT_DIPOLE
FLUX_ORDER
SHAPE_ORDER
registry

Methods Summary

doClassify(measRecord, chi2val) Classify a source as a dipole.
fail(measRecord[, error]) Catch failures and set the correct flags.
getExecutionOrder() Set execution order to FLUX_ORDER.
getLogName()
getTransformClass() Get the measurement transformation appropriate to this plugin.
measure(measRecord, exposure[, posExp, negExp]) Perform the non-linear least squares minimization on the putative dipole source.
measureN(measCat, exposure) Measure the properties of blended sources on a single image.

Attributes Documentation

APCORR_ORDER = 3.0
CENTROID_ORDER = 0.0
DEFAULT_CATALOGCALCULATION = 4.0
FAILURE_EDGE = 1
FAILURE_FIT = 2
FAILURE_NOT_DIPOLE = 4
FLUX_ORDER = 2.0
SHAPE_ORDER = 1.0
registry = <lsst.meas.base.pluginRegistry.PluginRegistry object>

Methods Documentation

doClassify(measRecord, chi2val)

Classify a source as a dipole.

Parameters:
measRecord : TODO: DM-17458

TODO: DM-17458

chi2val : TODO: DM-17458

TODO: DM-17458

Notes

Sources are classified as dipoles, or not, according to three criteria:

  1. Does the total signal-to-noise surpass the minSn?
  2. Are the pos/neg fluxes greater than 1.0 and no more than 0.65 (maxFluxRatio) of the total flux? By default this will never happen since posFlux == negFlux.
  3. Is it a good fit (chi2dof < 1)? (Currently not used.)
fail(measRecord, error=None)

Catch failures and set the correct flags.

classmethod getExecutionOrder()

Set execution order to FLUX_ORDER.

This includes algorithms that require both getShape() and getCentroid(), in addition to a Footprint and its Peaks.

getLogName()
static getTransformClass()

Get the measurement transformation appropriate to this plugin.

This returns a subclass of transforms.MeasurementTransform, which may be instantiated with details of the algorithm configuration and then called with information about calibration and WCS to convert from raw measurement quantities to calibrated units. Calibrated data is then provided in a separate output table.

Notes

By default, we copy everything from the input to the output without transformation.

measure(measRecord, exposure, posExp=None, negExp=None)

Perform the non-linear least squares minimization on the putative dipole source.

Parameters:
measRecord : lsst.afw.table.SourceRecord

diaSources that will be measured using dipole measurement

exposure : lsst.afw.image.Exposure

Difference exposure on which the diaSources were detected; exposure = posExp-negExp If both posExp and negExp are None, will attempt to fit the dipole to just the exposure with no constraint.

posExp : lsst.afw.image.Exposure, optional

“Positive” exposure, typically a science exposure, or None if unavailable When posExp is None, will compute posImage = exposure + negExp.

negExp : lsst.afw.image.Exposure, optional

“Negative” exposure, typically a template exposure, or None if unavailable When negExp is None, will compute negImage = posExp - exposure.
Returns:
result : TODO: DM-17458

TODO: DM-17458

Notes

The main functionality of this routine was placed outside of this plugin (into DipoleFitAlgorithm.fitDipole()) so that DipoleFitAlgorithm.fitDipole() can be called separately for testing (@see tests/testDipoleFitter.py)

measureN(measCat, exposure)

Measure the properties of blended sources on a single image.

This operates on all members of a blend family at once. The image may be from a single epoch, or it may be a coadd.

Parameters:
measCat : lsst.afw.table.SourceCatalog

Catalog describing the objects (and only those objects) being measured. Previously-measured quantities will be retrieved from here, and it will be updated in-place with the outputs of this plugin.

exposure : lsst.afw.image.ExposureF

The pixel data to be measured, together with the associated PSF, WCS, etc. All other sources in the image should have been replaced by noise according to deblender outputs.

Notes

Derived classes that do not implement measureN should just inherit this disabled version. Derived classes that do implement measureN should additionally add a bool doMeasureN config field to their config class to signal that measureN-mode is available.