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Hermes DRS
6.0
reduction software
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Hermes DRS
6.0
reduction software
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Subtract bias from exposed image part and estimate read-out noise. More...
Public Member Functions | |
| def | __init__ |
| Make a Hermes component and initialize variables. | |
| def | optionsAreValid |
| check we have the options, or set defaults. More... | |
| def | __call__ |
| run the module | |
 Public Member Functions inherited from hermes.pipeline.core.pipelinecomponent.PipelineComponent | |
| def | __init__ |
| def | __call__ |
| def | optionsAreValid |
| def | getOptions |
| def | setOptions |
| def | checkExistShapeUnits |
| def | isOption |
Public Attributes | |
| isDebug | |
| default values for options More... | |
| results | |
| subtractBias | |
| subtractBias is mandatory More... | |
| readoutNoise | |
| readoutNoise is mandatory More... | |
| suspectBiasLevel | |
| suspectBiasLevel is mandatory | |
| suspectReadoutNoiseLevel | |
| suspectReadoutNoiseLevel is mandatory | |
| biasToleranceFromDefault | |
| biasToleranceFromDefault is mandatory | |
| readoutNoiseToleranceFromDefault | |
| readoutNoiseToleranceFromDefault is mandatory | |
| prescanBiasADU | |
| prescanReadoutNoiseADU | |
| get prescanReadoutNoiseADU from previous module or use default | |
| Public Attributes inherited from hermes.pipeline.core.pipelinecomponent.PipelineComponent | |
| options | |
| logger | |
| ConsoleLogSeverity | |
| default value | |
| canShowGraphics | |
| when machine does not run matplotlib. More... | |
Subtract bias from exposed image part and estimate read-out noise.
PURPOSE :
This module subtracts the bias value from the input image (in ADU units) and
estimates the read-out noise (in ADU units). For the bias value, as well as
for the read-out noise (though independently), three options exist:
(a) select the value from the prescan region of the image (as computed by
computeBiasPrescanADU); this corresponds to the options \n
OptionDict.subtractBias = prescan \n
OptionDict.readoutNoise = prescan (NOT recommended) \n
(b) select the default value associated with the instrument model; this
corresponds to the options \n
OptionDict.subtractBias = default \n
OptionDict.readoutNoise = default \n
(c) let the choice depend on the difference between the prescan
value (a) and the default value (b). This corresponds to the options \n
OptionDict.subtractBias = conditional \n
OptionDict.readoutNoise = conditional
(c.1) If the absolute value of the difference between the two
values (a) and (b) does not exceed the prescribed tolerance
value 'biasToleranceFromDefault', then use the default value.
The philosophy of this choice is that the default values based on
the measurement of a stack of bias frames are more accurate than
those measured in the prescan region of a single frame (especially
true concerning the read-out noise).
(c.2) If the absolute value of the difference is significant, then
use the value from the prescan region.
Any other value of 'OptionDict.subtractBias' is interpreted
as "default", and an info message is given. \n
(c.3) If the bias or the read-out noise estimated from the prescan
region is grossly inconsistent with the default values, indicating
that the detector is misbehaving, then treatment of the image will
be stopped #SUGG and a warning will be issued.
The relevant differences with the default values are put
in 'model.suspectBiasLevel' and 'model.suspectReadoutNoiselevel'.
######## : NOTE : no writing in the model should been allowed at all !!!!!!!
COMMENTS :
SYNTAX :
INPUT CONSTANTS FROM INSTRUMENT MODEL :
MANDATORY :
defaultPrescanBiasADU
defaultReadoutNoiseADU
biasOffset
INPUT DATA FROM RESULTDICT :
MANDATORY :
image
obtained from a rawimage with the "cutPrescan" component
numberOfImagesInStack should be 1
other values will end the execution and raise the
"TooManyFilesToHandle" flag
OPTIONAL :
prescanBiasADU
prescanReadoutNoiseADU
Both those values should come
from previous module "computebiasprescan"
If not present, default values will be used.
OPTIONS READ FROM OPTIONDICT :
MANDATORY :
subtractBias
"default"
"prescan"
or "conditional"
readoutNoise
"default"
"prescan"
or "conditional"
suspectBiasLevel
suspectReadoutNoiseLevel
biasToleranceFromDefault
readoutNoiseToleranceFromDefault
OPTIONAL :
isDebug (Boolean : True or False)
default value : False
writes a fits file with the results
image in 'T15image.fits')
OUTPUT WRITTEN IN RESULTDICT
When success condition is met :
image
subtractBias : used option for estimation of the bias level
readoutNoise : used option for estimation of readout noise
When success condition is not met :
record the fatal error message and stop the chain.
SUCCESS CONDITIONS :
OPTIONS are tested before execution of the component, and
some values are making that execution impossible. | def hermes.pipeline.components.subtractbiasCCD.subtractBiasCCD.optionsAreValid | ( | self, | |
| optionDict | |||
| ) |
check we have the options, or set defaults.
| hermes.pipeline.components.subtractbiasCCD.subtractBiasCCD.isDebug |
default values for options
isDebug is False by default.
When set to True, intermediate files are written in the debug folder. This is meant to let the user find out why his results are not the expected ones. Usually it reflects a change in the instrument that has to be fixed.
| hermes.pipeline.components.subtractbiasCCD.subtractBiasCCD.readoutNoise |
readoutNoise is mandatory
otherwise, we choose to apply the ron measured in the prescan region
subtraction of the default bias, when appropriate.
TODO : test if int(image) works and if the subtract of a constant works on it find out which option for the readout noise estimate was selected for most cases, use standard value
| hermes.pipeline.components.subtractbiasCCD.subtractBiasCCD.subtractBias |
subtractBias is mandatory
find out whether either the bias level measured in the prescan region, or the read-out noise measured in the prescan region is suspect
find out which option for the bias estimate was selected
1.8.6