DeferredChargeTask¶

Bases: 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.
`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.
`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:

ampDatanumpy.ndarray, (nx, ny): Image data to flip.
amplsst.afw.cameraGeom.Amplifier: Amplifier to get readout corner information.

Returns:

ampDatanumpy.ndarray, (nx, ny): Flipped image data.

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.

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:

{A_L s'(m, n - j) exp(-j t / \tau_L)}_j=0^jmax

Parameters:

inputArrnumpy.ndarray, (nx, ny): Input image data to correct.
drift_scalefloat: Drift scale (Snyder+21 A_L value) to use in correction.
decay_timefloat: Decay time (Snyder+21 tau_L) of the correction.
num_previous_pixelsint, 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:

outputArrnumpy.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:

{A_L s'(m, n - j) exp(-j t / \tau_L)}_j=0^jmax

Parameters:

inputArrnumpy.ndarray, (nx, ny): Input image data to correct.
traplsst.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_pixelsint, optional: Number of previous pixels to use for correction.

Returns:

outputArrnumpy.ndarray, (nx, ny): Corrected image data.

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(exposure, ctiCalib, gains=None)¶

Correct deferred charge/CTI issues.

Parameters:

exposurelsst.afw.image.Exposure: Exposure to correct the deferred charge on.
ctiCaliblsst.ip.isr.DeferredChargeCalib: Calibration object containing the charge transfer inefficiency model.
gainsdict [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:

exposurelsst.afw.image.Exposure: The corrected exposure.

Notes

This task will read the exposure metadata and determine if applying gains if necessary. The correction takes place in units of electrons. If bootstrapping, the gains used will just be 1.0. and the input/output units will stay in adu. If the input image is in adu, the output image will be in units of electrons. If the input image is in electron, the output image will be in electron.

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.

Navigation

DeferredChargeTask¶