LinearitySolveTask

LinearitySolveTask constructs a linearity correction model (a Linearizer) based on the results stored in the input photon transfer curve (PTC) dataset.

Processing summary

LinearitySolveTask runs these operations:

1. Convert the input exposure time/photodiode flux measurement to a proxy flux by fitting the low-flux end with a linear fit.
2. Perform fit against using the observed flux and this linear proxy flux (using either a spline or a polynomial).
3. Store the correction, such that the corrected flux is equal to the uncorrected flux + the linearity correction as a function of the uncorrected flux.

Python API summary

from lsst.cp.pipe.linearity import LinearitySolveTask

classLinearitySolveTask(*, config=None, log=None, initInputs=None, **kwargs)

Fit the linearity from the PTC dataset...

attributeconfig

Access configuration fields and retargetable subtasks.

methodrun(inputPtc, dummy, camera, inputDims)

Fit non-linearity to PTC data, returning the correct Linearizer object...

See also

See the LinearitySolveTask API reference for complete details.

Retargetable subtasks

No subtasks.

Configuration fields

connections

Data type

lsst.pipe.base.config.Connections

Field type

ConfigField

Configurations describing the connections of the PipelineTask to datatypes

ignorePtcMask

Default

False

Field type

bool Field

Ignore the expIdMask set by the PTC solver?

linearityType

Default

'Squared'

Field type

str ChoiceField (optional)

Choices

'LookupTable'

Create a lookup table solution.

'Polynomial'

Create an arbitrary polynomial solution.

'Squared'

Create a single order squared solution.

'Spline'

Create a spline based solution.

'None'

Create a dummy solution.

None

Field is optional

Type of linearizer to construct.

maxLinearAdu

Default

20000.0

Field type

float Field

Maximum DN value to use to estimate linear term.

maxLookupTableAdu

Default

262144

Field type

int Field

Maximum DN value for a LookupTable linearizer.

minLinearAdu

Default

2000.0

Field type

float Field

Minimum DN value to use to estimate linear term.

nSigmaClipLinear

Default

5.0

Field type

float Field

Maximum deviation from linear solution for Poissonian noise.

polynomialOrder

Default

3

Field type

int Field

Degree of polynomial to fit.

saveLogOutput

Default

True

Field type

bool Field

Flag to enable/disable saving of log output for a task, enabled by default.

saveMetadata

Default

True

Field type

bool Field

Flag to enable/disable metadata saving for a task, enabled by default.

splineKnots

Default

10

Field type

int Field

Number of spline knots to use in fit.

Debugging

linearFit

Display the linearity solution after the initial linear fit (bool)?

polyFit

Display the linearity solution after generating the polynomial fit (bool)?

splineFit

Display the linearity solution after generating the spline fit (bool)?

solution

Display the final linearity solution (bool)?