AstrometryTask

class lsst.meas.astrom.AstrometryTask(refObjLoader=None, schema=None, **kwargs)

Bases: RefMatchTask

Match an input source catalog with objects from a reference catalog and solve for the WCS.

This task is broken into two main subasks: matching and WCS fitting which are very interactive. The matching here can be considered in part a first pass WCS fitter due to the fitter’s sensitivity to outliers.

Parameters:
refObjLoaderlsst.meas.algorithms.ReferenceLoader

A reference object loader object; gen3 pipeline tasks will pass None and call setRefObjLoader in runQuantum.

schemalsst.afw.table.Schema

Used to set “calib_astrometry_used” flag in output source catalog.

**kwargs

Additional keyword arguments for pipe_base lsst.pipe.base.Task.__init__.

Methods Summary

emptyMetadata()

Empty (clear) the metadata for this Task and all sub-Tasks.

getFullMetadata()

Get metadata for all tasks.

getFullName()

Get the task name as a hierarchical name including parent task names.

getName()

Get the name of the task.

getTaskDict()

Get a dictionary of all tasks as a shallow copy.

loadAndMatch(exposure, sourceCat)

Load reference objects overlapping an exposure and match to sources detected on that exposure.

makeField(doc)

Make a lsst.pex.config.ConfigurableField for this task.

makeSubtask(name, **keyArgs)

Create a subtask as a new instance as the name attribute of this task.

run(sourceCat, exposure)

Load reference objects, match sources and optionally fit a WCS.

setRefObjLoader(refObjLoader)

Sets the reference object loader for the task.

solve(exposure, sourceCat)

Load reference objects overlapping an exposure, match to sources and fit a WCS

timer(name[, logLevel])

Context manager to log performance data for an arbitrary block of code.

Methods Documentation

emptyMetadata() None

Empty (clear) the metadata for this Task and all sub-Tasks.

getFullMetadata() TaskMetadata

Get metadata for all tasks.

Returns:
metadataTaskMetadata

The keys are the full task name. Values are metadata for the top-level task and all subtasks, sub-subtasks, etc.

Notes

The returned metadata includes timing information (if @timer.timeMethod is used) and any metadata set by the task. The name of each item consists of the full task name with . replaced by :, followed by . and the name of the item, e.g.:

topLevelTaskName:subtaskName:subsubtaskName.itemName

using : in the full task name disambiguates the rare situation that a task has a subtask and a metadata item with the same name.

getFullName() str

Get the task name as a hierarchical name including parent task names.

Returns:
fullNamestr

The full name consists of the name of the parent task and each subtask separated by periods. For example:

  • The full name of top-level task “top” is simply “top”.

  • The full name of subtask “sub” of top-level task “top” is “top.sub”.

  • The full name of subtask “sub2” of subtask “sub” of top-level task “top” is “top.sub.sub2”.

getName() str

Get the name of the task.

Returns:
taskNamestr

Name of the task.

See also

getFullName

Get the full name of the task.

getTaskDict() dict[str, weakref.ReferenceType[lsst.pipe.base.task.Task]]

Get a dictionary of all tasks as a shallow copy.

Returns:
taskDictdict

Dictionary containing full task name: task object for the top-level task and all subtasks, sub-subtasks, etc.

loadAndMatch(exposure, sourceCat)

Load reference objects overlapping an exposure and match to sources detected on that exposure.

Parameters:
exposurelsst.afw.image.Exposure

exposure that the sources overlap

sourceCatlsst.afw.table.SourceCatalog.

catalog of sources detected on the exposure

Returns:
resultlsst.pipe.base.Struct

Result struct with Components:

Notes

ignores config.matchDistanceSigma

classmethod makeField(doc: str) ConfigurableField

Make a lsst.pex.config.ConfigurableField for this task.

Parameters:
docstr

Help text for the field.

Returns:
configurableFieldlsst.pex.config.ConfigurableField

A ConfigurableField for this task.

Examples

Provides a convenient way to specify this task is a subtask of another task.

Here is an example of use:

class OtherTaskConfig(lsst.pex.config.Config):
    aSubtask = ATaskClass.makeField("brief description of task")
makeSubtask(name: str, **keyArgs: Any) None

Create a subtask as a new instance as the name attribute of this task.

Parameters:
namestr

Brief name of the subtask.

**keyArgs

Extra keyword arguments used to construct the task. The following arguments are automatically provided and cannot be overridden:

  • config.

  • parentTask.

Notes

The subtask must be defined by Task.config.name, an instance of ConfigurableField or RegistryField.

run(sourceCat, exposure)

Load reference objects, match sources and optionally fit a WCS.

This is a thin layer around solve or loadAndMatch, depending on config.forceKnownWcs.

Parameters:
exposurelsst.afw.image.Exposure

exposure whose WCS is to be fit The following are read only:

  • bbox

  • filter (may be unset)

  • detector (if wcs is pure tangent; may be absent)

The following are updated:

  • wcs (the initial value is used as an initial guess, and is required)

sourceCatlsst.afw.table.SourceCatalog

catalog of sources detected on the exposure

Returns:
resultlsst.pipe.base.Struct

with these fields:

  • refCat : reference object catalog of objects that overlap the exposure (with some margin) (lsst.afw.table.SimpleCatalog).

  • matches : astrometric matches (list of lsst.afw.table.ReferenceMatch).

  • scatterOnSky : median on-sky separation between reference objects and sources in “matches” (lsst.afw.geom.Angle) or None if config.forceKnownWcs True

  • matchMeta : metadata needed to unpersist matches (lsst.daf.base.PropertyList)

setRefObjLoader(refObjLoader)

Sets the reference object loader for the task.

Parameters:
refObjLoader

An instance of a reference object loader task or class.

solve(exposure, sourceCat)

Load reference objects overlapping an exposure, match to sources and fit a WCS

Returns:
resultlsst.pipe.base.Struct

Result struct with components:

  • refCat : reference object catalog of objects that overlap the exposure (with some margin) (lsst::afw::table::SimpleCatalog).

  • matches : astrometric matches (list of lsst.afw.table.ReferenceMatch).

  • scatterOnSky : median on-sky separation between reference objects and sources in “matches” (lsst.geom.Angle)

  • matchMeta : metadata needed to unpersist matches (lsst.daf.base.PropertyList)

Raises:
BadAstrometryFit

If the measured mean on-sky distance between the matched source and reference objects is greater than self.config.maxMeanDistanceArcsec.

Notes

ignores config.forceKnownWcs

timer(name: str, logLevel: int = 10) Iterator[None]

Context manager to log performance data for an arbitrary block of code.

Parameters:
namestr

Name of code being timed; data will be logged using item name: Start and End.

logLevelint

A logging level constant.

See also

lsst.utils.timer.logInfo

Implementation function.

Examples

Creating a timer context:

with self.timer("someCodeToTime"):
    pass  # code to time