PhotonTransferCurveSolveTask

PhotonTransferCurveSolveTask combines the partial photon transfer curve (PTC) datasets from pairs of flats, and produces the complete curve, fitting the gains, read noises, and measuring the covariances.

Processing summary

PhotonTransferCurveSolveTask runs these operations:

1. Collates the multiple single-pair input PTC datasets.
2. Fits either a full-covariance model, or one of two simpler approximations (polynomial and Astier+19 exponential approximation).
3. Persists the final complete dataset to disk.

Python API summary

from lsst.cp.pipe.ptc.cpSolvePtcTask import PhotonTransferCurveSolveTask

classPhotonTransferCurveSolveTask(*args, **kwargs)

Task to fit the PTC from flat covariances...

attributeconfig

Access configuration fields and retargetable subtasks.

methodrun(inputCovariances, camera=None, detId=0)

Fit measured covariances to different models...

See also

See the PhotonTransferCurveSolveTask 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

consecutivePointsVarDecreases

Default

2

Field type

int RangeField

Range

[2,inf)

Required number of consecutive points/fluxes in the PTC where the variance decreases in order to find a first estimate of the PTC turn-off.

doFitBootstrap

Default

False

Field type

bool Field

Use bootstrap for the PTC fit parameters and errors?.

maxIterFullFitCovariancesAstier

Default

3

Field type

int Field

Maximum number of iterations in full model fit for FULLCOVARIANCE ptcFitType

maxIterationsPtcOutliers

Default

2

Field type

int RangeField

Range

[0,inf)

Maximum number of iterations for outlier rejection in PTC.

maximumRangeCovariancesAstier

Default

8

Field type

int Field

Maximum range of covariances as in Astier+19

minVarPivotSearch

Default

10000

Field type

float Field

The code looks for a pivot signal point after which the variance starts decreasing at high-flux to exclude then from the PTC model fit. However, sometimes at low fluxes, the variance decreases slightly. Set this variable for the variance value, in ADU^2, after which the pivot should be sought.

polynomialFitDegree

Default

3

Field type

int Field

Degree of polynomial to fit the PTC, when ‘ptcFitType’=POLYNOMIAL.

ptcFitType

Default

'POLYNOMIAL'

Field type

str ChoiceField (optional)

Choices

'POLYNOMIAL'

n-degree polynomial (use ‘polynomialFitDegree’ to set ‘n’).

'EXPAPPROXIMATION'

Approximation in Astier+19 (Eq. 16).

'FULLCOVARIANCE'

Full covariances model in Astier+19 (Eq. 20)

None

Field is optional

Fit PTC to Eq. 16, Eq. 20 in Astier+19, or to a polynomial.

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.

sigmaClipFullFitCovariancesAstier

Default

5.0

Field type

float Field

sigma clip for full model fit for FULLCOVARIANCE ptcFitType

sigmaCutPtcOutliers

Default

5.0

Field type

float Field

Sigma cut for outlier rejection in PTC.