CALPRODUCT-VS-004: VIS Brighter-fatter Effect (BFE)

Parent requirement

Not yet in the CalCD-B

Scheduling

Once, during PV.

Time-critical

No

Objective

Increasing amounts of charges in the potential well of a pixel change the physical boundaries of a pixel, effectively shrinking it. Photons arriving from the same source at a late time during an exposure therefore create photo-electrons in a neighboring pixel.

This can be recognized by an increase of stellar FWHM with flux, and also by a decrease of pixel-to-pixel variance in flat fields at higher illumination (flattening of the CALPRODUCT-VS-011: VIS Photon Transfer Curve (PTC)).

The effect directly impacts the PSF models and therefore the shear measurement, and is possibly subject to radiation damage. It is achromatic in nature.

Fulfilled by

CALBLOCK-PV-001: Self Calibration (providing stellar field)

CALBLOCK-PV-022: VIS PRNU and Brighter-fatter Effect

CALBLOCK-PV-029: VIS Photon Transfer Curve and CTI/EPER (also)

CALBLOCK-F-006: Wide Survey (providing flats)

CALBLOCK-F-001: Self Calibration (providing stellar field)

Data volume

TBD

Processing input

Ground Processing Input Data:

Data Description:

Processing method

Extrapolate the PRNU to zero value, using the flats at three different fluences. Must take into account that the brighter-fatter effect is modified by charge diffusion and charge transfer inefficiency.

Processing output

BFE kernel for each detector quadrant.

Required accuracy, constraints

TBW

Processing tools

TBD

Validation

Compare the brighter-fatter kernels with those obtained on ground, and update if necessary.

Recovery

Update the brighter-fatter model used to correct the PSF and shear data.

Quality control parameters

DataModel: https://gitlab.euclid-sgs.uk/

Contact person

VIS instrument scientist