AstrometryTask

class lsst.meas.astrom.AstrometryTask(refObjLoader, 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

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

getTaskDict() → Dict[str, ReferenceType[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:

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

• matches : Matched sources and references (list of lsst.afw.table.ReferenceMatch)

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

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:

TaskError

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.

logLevel

A logging level constant.

See also

timer.logInfo

Examples

Creating a timer context:

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