psfDeterminer.py

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#
# LSST Data Management System
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# Copyright 2008-2017  AURA/LSST.
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# This product includes software developed by the
# LSST Project (http://www.lsst.org/).
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__all__ = ["BasePsfDeterminerConfig", "BasePsfDeterminerTask", "psfDeterminerRegistry"]

import abc

import lsst.pipe.base as pipeBase
import lsst.pex.config as pexConfig


class BasePsfDeterminerConfig(pexConfig.Config):
    """Configuration that is likely to be shared by all PSF determiners

    This is fairly sparse; more fields can be moved here once it is clear they are universal.
    """
    kernelSize = pexConfig.Field(
        doc="radius of the kernel to create, relative to the square root of the stellar quadrupole moments",
        dtype=float,
        default=10.0,
    )
    kernelSizeMin = pexConfig.Field(
        doc="Minimum radius of the kernel",
        dtype=int,
        default=25,
    )
    kernelSizeMax = pexConfig.Field(
        doc="Maximum radius of the kernel",
        dtype=int,
        default=45,
    )


class BasePsfDeterminerTask(pipeBase.Task, metaclass=abc.ABCMeta):
    """!Base class for PSF determiners

    Register all PSF determiners with the psfDeterminerRegistry using:
        psfDeterminerRegistry.register(name, class)
    """

    usesMatches = False  # Does the PSF determiner use the "matches" argument in the "run method? Few do.
    ConfigClass = BasePsfDeterminerConfig
    _DefaultName = "psfDeterminer"

    def __init__(self, config, schema=None, **kwds):
        """Construct a PSF Determiner

        @param[in]       config   an instance of pexConfig.Config that configures this algorithm
        @param[in,out]   schema   an instance of afw.table.Schema used for sources; passing a
                                  schema allows the determiner to reserve a flag field to mark stars
                                  used in PSF measurement, but some PSF determiners ignore this argument
        """
        pipeBase.Task.__init__(self, config=config, **kwds)

    @abc.abstractmethod
    def determinePsf(self, exposure, psfCandidateList, metadata=None):
        """Determine a PSF model

        @param[in] exposure            exposure containing the psf candidates (lsst.afw.image.Exposure)
        @param[in] psfCandidateList:   a sequence of PSF candidates (each an
                                       lsst.meas.algorithms.PsfCandidate); typically obtained by
                                       detecting sources and then running them through a star selector
        @param[in,out] metadata        a place to save interesting items

        @return
            - psf: the fit PSF; a subclass of lsst.afw.detection.Psf
            - cellSet: the spatial cell set used to determine the PSF (lsst.afw.math.SpatialCellSet)
        """
        raise NotImplementedError("BasePsfDeterminerTask is abstract, subclasses must override this method")


psfDeterminerRegistry = pexConfig.makeRegistry(
    doc="A registry of PSF determiners (subclasses of BasePsfDeterminerTask)",
)