CALPRODUCT-NI-003: NISP Brighter-fatter Effect¶
Parent requirement¶
Not yet in the CalCD-B
Scheduling¶
Monthly.
Time-critical¶
No.
Dependencies¶
None
Objective¶
Characterize the brighter-fatter effect (BFE) and check for any variations over time. BFE kernels can be derived from the variance in flat fields of increasing fluence, and tested directly by comparing against the observed FWHM of stars of different magnitude.
IPC and charge diffusion can mask the BFE to some extent. BFE is also not completely flux conserving, acting as an additional source of nonlinearity.
BFE can be considerable, e.g. it changes the PSF width in H2RGs by up to 5%, and is a continuous function of flux.
https://iopscience.iop.org/article/10.1088/1748-0221/12/04/C04009
Fulfilled by¶
CALBLOCK-PV-001: Self Calibration
Instrument configuration¶
Instrument: RSD
Data volume¶
180*NP*3 = 47520 MB from CALBLOCK-F-001: Self Calibration images in three filters.
750*NP = 66000 MB from CALBLOCK-PV-010: NISP LED flats images.
Processing input¶
Static bad pixel map (dead, disconnected, hot, permanently high persistence, etc)
Dark current map (warm and hot pixels)
Baseline map (pixels with limited dynamic range due to high bias level)
Nonlinearity map
LED flat fields
Pixels with high random telegraph noise (RTN, if available)
Ground Processing Input Data: Dark, nonlinearity, small-scale flat, persistence map, static bad pixel map
Data Description:
Processing method¶
TBD
Processing output¶
BFE kernels from the LED flats. Direct measurement of BFE as a function of source magnitude (increase of FWHM as a function of source flux), and, provided sufficient spatial sampling, detector position.
Required accuracy, constraints¶
To be established after a few months of in-flight data are available.
Processing tools¶
TBD
Validation¶
Significant and sudden changes are not expected, as BFE roots directly in the pixel hardware. Sudden and significant changes would likely have their origin elsewhere (electronics, software, erroneous data processing) and must be investigated.
At the time of writing, no publications are known that investigate the temporal evolution of the brighter-fatter effect due to prolonged radiation exposure. Therefore, the amplitude of a change considered problematic can only be given once a few months of in-flight data have become available.
Recovery¶
Repeat at the next possible opportunity.
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Contact person¶
NISP-P calibration scientist