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 singlepair input PTC datasets.
Fits either a fullcovariance 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

class
PhotonTransferCurveSolveTask
(*, config=None, log=None, initInputs=None, **kwargs) Task to fit the PTC from flat covariances
...
 attributeconfig
Access configuration fields and retargetable subtasks.
See also
See the PhotonTransferCurveSolveTask
API reference for complete details.
Retargetable subtasks¶
No subtasks.
Configuration fields¶
binSize¶
Bin the image by this factor in both dimensions.
connections¶
 Data type
lsst.pipe.base.config.PhotonTransferCurveSolveConfigConnections
 Field type
Configurations describing the connections of the PipelineTask to datatypes
consecutivePointsVarDecreases¶
 Default
2
 Field type
 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 turnoff. Only used if doLegacyTurnoffSelection is True.
doFitBootstrap¶
Use bootstrap for the PTC fit parameters and errors?.
doLegacyTurnoffSelection¶
Use ‘legacy’ computation for PTC turnoff selection. If set to False, then the KS test pvalue selection will be used instead.
doSubtractLongRangeCovariances¶
Subtract longrange covariances before FULLCOVARIANCE fit, beyond startLongRangeCovariances?
ksTestMinPvalue¶
Minimum value of the Gaussian histogram KS test pvalue to be used in PTC fit. Only used if doLegacyTurnoffSelection is False.
maxIterFullFitCovariancesAstier¶
Maximum number of iterations in full model fit for FULLCOVARIANCE ptcFitType
maxIterationsPtcOutliers¶
 Default
2
 Field type
 Range
[0,inf)
Maximum number of iterations for outlier rejection in PTC.
maxMeanSignal¶
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¶
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¶
Maximum range of measured covariances as in Astier+19
maximumRangeCovariancesAstierFullCovFit¶
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¶
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¶
The code looks for a pivot signal point after which the variance starts decreasing at highflux 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¶
If doSubtractLongRangeCovariances is True, polynomial degree to fit data beyond startLongRangeCovariances.
polynomialFitDegree¶
Degree of polynomial to fit the PTC, when ‘ptcFitType’=POLYNOMIAL.
ptcFitType¶
 Default
'POLYNOMIAL'
 Field type
str
ChoiceField
(optional) Choices
'POLYNOMIAL'
ndegree 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¶
Flag to enable/disable saving of log output for a task, enabled by default.
scaleMaxSignalInitialPtcOutlierFit¶
Scale maxSignalInitialPtcOutlierFit by approximate gain? If yes then maxSignalInitialPtcOutlierFit is assumed to have units of electrons, otherwise ADU.
sigmaClipFullFitCovariancesAstier¶
sigma clip for full model fit for FULLCOVARIANCE ptcFitType
sigmaCutPtcOutliers¶
Sigma cut for outlier rejection in PTC.
startLongRangeCovariances¶
If doSubtractLongRangeCovariances is True, subtract covariances beyond this range. It should be less than maximumRangeCovariancesAstier.