DeferredChargeTask¶

class lsst.ip.isr.DeferredChargeTask(config: Optional[Config] = None, name: Optional[str] = None, parentTask: Optional[Task] = None, log: Optional[Union[logging.Logger, lsst.utils.logging.LsstLogAdapter]] = None)¶

Bases: lsst.pipe.base.Task

Task to correct an exposure for charge transfer inefficiency.

This uses the methods described by Snyder et al. 2021, Journal of Astronimcal Telescopes, Instruments, and Systems, 7, 048002. doi:10.1117/1.JATIS.7.4.048002 (Snyder+21).

Methods Summary

`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`flipData`(ampData, amp)	Flip data array such that readout corner is at lower-left.
`getAllSchemaCatalogs`()	Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.
`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.
`getSchemaCatalogs`()	Get the schemas generated by this task.
`getTaskDict`()	Get a dictionary of all tasks as a shallow copy.
`local_offset_inverse`(inputArr, drift_scale, …)	Remove CTI effects from local offsets.
`local_trap_inverse`(inputArr, trap[, …])	Apply localized trapping inverse operator to pixel signals.
`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`(exposure, ctiCalib[, gains])	Correct deferred charge/CTI issues.
`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.

static flipData(ampData, amp)¶

Flip data array such that readout corner is at lower-left.

Parameters:	ampData : `numpy.ndarray`, (nx, ny) Image data to flip. amp : `lsst.afw.cameraGeom.Amplifier` Amplifier to get readout corner information.
Returns:	ampData : `numpy.ndarray`, (nx, ny) Flipped image data.

getAllSchemaCatalogs() → Dict[str, Any]¶

Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.

Returns:	schemacatalogs : `dict` Keys are butler dataset type, values are a empty catalog (an instance of the appropriate `lsst.afw.table` Catalog type) for all tasks in the hierarchy, from the top-level task down through all subtasks.

Notes

This method may be called on any task in the hierarchy; it will return the same answer, regardless.

The default implementation should always suffice. If your subtask uses schemas the override Task.getSchemaCatalogs, not this method.

getFullMetadata() → lsst.pipe.base._task_metadata.TaskMetadata¶

Get metadata for all tasks.

Returns:	metadata : `TaskMetadata` 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:	fullName : `str` 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:	taskName : `str` Name of the task.

See also

Task.getAllSchemaCatalogs

Notes

Warning

Subclasses that use schemas must override this method. The default implementation returns an empty dict.

This method may be called at any time after the Task is constructed, which means that all task schemas should be computed at construction time, not when data is actually processed. This reflects the philosophy that the schema should not depend on the data.

Returning catalogs rather than just schemas allows us to save e.g. slots for SourceCatalog as well.

getTaskDict() → Dict[str, weakref]¶

Get a dictionary of all tasks as a shallow copy.

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

static local_offset_inverse(inputArr, drift_scale, decay_time, num_previous_pixels=15)¶

Remove CTI effects from local offsets.

This implements equation 10 of Snyder+21. For an image with CTI, s’(m, n), the correction factor is equal to the maximum value of the set of:

Parameters:

inputArr : numpy.ndarray, (nx, ny): Input image data to correct.
drift_scale : float: Drift scale (Snyder+21 A_L value) to use in correction.
decay_time : float: Decay time (Snyder+21 tau_L) of the correction.
num_previous_pixels : int, optional: Number of previous pixels to use for correction. As the CTI has an exponential decay, this essentially truncates the correction where that decay scales the input charge to near zero.

Returns:

outputArr : numpy.ndarray, (nx, ny): Corrected image data.

static local_trap_inverse(inputArr, trap, global_cti=0.0, num_previous_pixels=6)¶

Apply localized trapping inverse operator to pixel signals.

This implements equation 13 of Snyder+21. For an image with CTI, s’(m, n), the correction factor is equal to the maximum value of the set of:

Parameters:	inputArr : `numpy.ndarray`, (nx, ny) Input image data to correct. trap : `lsst.ip.isr.SerialTrap` Serial trap describing the capture and release of charge. global_cti: `float` Mean charge transfer inefficiency, b from Snyder+21. num_previous_pixels : `int`, optional Number of previous pixels to use for correction.
Returns:	outputArr : `numpy.ndarray`, (nx, ny) Corrected image data.

classmethod makeField(doc: str) → lsst.pex.config.configurableField.ConfigurableField¶

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

Parameters:	doc : `str` Help text for the field.
Returns:	configurableField : `lsst.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) → None¶

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

Parameters:	name : `str` 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(exposure, ctiCalib, gains=None)¶

Correct deferred charge/CTI issues.

Parameters:	exposure : `lsst.afw.image.Exposure` Exposure to correct the deferred charge on. ctiCalib : `lsst.ip.isr.DeferredChargeCalib` Calibration object containing the charge transfer inefficiency model. gains : `dict` [`str`, `float`] A dictionary, keyed by amplifier name, of the gains to use. If gains is None, the nominal gains in the amplifier object are used.
Returns:	exposure : `lsst.afw.image.Exposure` The corrected exposure.

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

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

Parameters:	name : `str` Name of code being timed; data will be logged using item name: `Start` and `End`. logLevel A `logging` level constant.

Navigation

DeferredChargeTask¶