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:

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

Python API summary¶

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

classPhotonTransferCurveSolveTask(*, config=None, log=None, initInputs=None, **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...

Retargetable subtasks¶

No subtasks.

Configuration fields¶

binSize¶

Default: 1
Field type: int Field

Bin the image by this factor in both dimensions.

connections¶

Data type: lsst.pipe.base.config.PhotonTransferCurveSolveConfigConnections
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. Only used if doLegacyTurnoffSelection is True.

doFitBootstrap¶

Default: False
Field type: bool Field

Use bootstrap for the PTC fit parameters and errors?.

doLegacyTurnoffSelection¶

Default: False
Field type: bool Field

Use ‘legacy’ computation for PTC turnoff selection. If set to False, then the KS test p-value selection will be used instead.

doSubtractLongRangeCovariances¶

Default: False
Field type: bool Field

Subtract long-range covariances before FULLCOVARIANCE fit, beyond startLongRangeCovariances?

ksTestMinPvalue¶

Default: 0.01
Field type: float Field

Minimum value of the Gaussian histogram KS test p-value to be used in PTC fit. Only used if doLegacyTurnoffSelection is False.

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.

maxMeanSignal¶

Default: {'ALL_AMPS': 1000000.0}
Field type: DictField
Key type: str
Value type: float

Maximum values (inclusive) of mean signal (in ADU) below which to consider, per amp. The same cut is applied to all amps if this dictionary is of the form {‘ALL_AMPS’: value}

maxSignalInitialPtcOutlierFit¶

Default: 50000.0
Field type: float Field

Maximum signal considered for intial outlier fit. This should be below the PTC turnoff to ensure accurate outlier rejection. If scaleMaxSignalInitialPtcOutlierFit=True then the units are electrons; otherwise ADU.

maximumRangeCovariancesAstier¶

Default: 8
Field type: int Field

Maximum range of measured covariances as in Astier+19

maximumRangeCovariancesAstierFullCovFit¶

Default: 8
Field type: int Field

Maximum range up to where to fit covariances as in Astier+19, for the FULLCOVARIANCE model.This is different from maximumRangeCovariancesAstier.It should be less or equal than maximumRangeCovariancesAstier.The number of parameters for this model is 3*maximumRangeCovariancesAstierFullCovFit^2 + 1, so increase with care so that the fit is not too slow.

minMeanSignal¶

Default: {'ALL_AMPS': 0.0}
Field type: DictField
Key type: str
Value type: float

Minimum values (inclusive) of mean signal (in ADU) per amp to use. The same cut is applied to all amps if this parameter [dict] is passed as {‘ALL_AMPS’: value}

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. Only used if doLegacyTurnoffSelection is True.

polyDegLongRangeCovariances¶

Default: 1
Field type: int Field

If doSubtractLongRangeCovariances is True, polynomial degree to fit data beyond startLongRangeCovariances.

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. Deprecated: This field is deprecated and will be removed after v26.

scaleMaxSignalInitialPtcOutlierFit¶

Default: True
Field type: bool Field

Scale maxSignalInitialPtcOutlierFit by approximate gain? If yes then maxSignalInitialPtcOutlierFit is assumed to have units of electrons, otherwise ADU.

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.

startLongRangeCovariances¶

Default: 4
Field type: int Field

If doSubtractLongRangeCovariances is True, subtract covariances beyond this range. It should be less than maximumRangeCovariancesAstier.

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