Details

Type: Story

Status: Done

Resolution: Done

Fix Version/s: None

Component/s: ip_isr

Labels:None

Story Points:5

Epic Link:

Team:Alert Production
Description
In the default IsrTask, the variance is currently set after dark subtraction. This means that photon noise from the dark is not included in the variance plane, which is incorrect. The variance should be set after bias subtraction and before dark subtraction.
HsinFang Chiang also points out (DM4191) that the AssembleCcdTask with default parameters requires amplifier images with variance planes, even though the variance cannot be set properly until after fullframe bias subtraction. I believe that AssembleCcdTask only requires a variance plane in the amp images because it does an "effective gain" calculation, but I suggest that this isn't very useful (an approximation of an approximation, and you're never going to use that information anyway because it's embedded in the variance plane with better fidelity). I therefore suggest that this effective gain calculation be stripped out and that AssembleCcdTask not require variance planes.
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Issue Links
 is triggered by

RFC282 Remove effective gain calculation from CCD assembly
 Implemented
Paul Price as reporter, I'd like to ask you to review this very small changeset. Let me know if you'd prefer not to do it.