CALPRODUCT-VS-020: VIS Blooming threshold¶
Parent requirement¶
Not in the CalCD-B
Scheduling¶
Once during PV. 60-day cycle within ROS during routine phase.
Time-critical¶
No
Objective¶
We distinguish three types of saturation:
Blooming, i.e. charges flowing over into neighboring pixels. This makes it a CTI effect controlled by the surface electronic fields / traps, and more complicated than bulk CTI (CALPRODUCT-VS-005: VIS CTI Charge Injection Lines, CALPRODUCT-VS-018: VIS Extended Pixel Edge Response (CTI-EPER)). Being a CTI, we expect it to degrade over time due to radiation damage. Blooming is observed as low as 120 ke- or 42 kADU.
Saturation of the readout electronics (16 bit ADC saturation, 150 ke- or 65 kADU)
Physical saturation of the pixel’s full well capacity (FWC saturation, 220 ke-).
Blooming therefore occurs first, and - being controlled by surface electronic fields - is variable across the detectors and within quadrants. The presence of blooming manifests itself in a drop of the PTC curve, e.g. detectable as a decrease of the variance in the difference image of two flat fields. This drop could be partially masked by other CTI effects.
The blooming theshold is expected to degrade over time due to radiation damage, and therefore must be monitored.
Fulfilled by¶
Data volume¶
Data Volume under study; compression ratio varies by a large factor depending on the fluence.
Processing input¶
Ground Processing Input Data:
Data Description:
Processing method¶
Compute the variance in the difference images of two flat fields, as a function of fluence.
Alternatively, divide the high-intensity flats by some low-intensity reference flats. Pixels near or in saturation clearly stand out from the rest.
Processing output¶
Updated blooming thresholds for each detector quadrant, if possible at higher spatial resolution by computing variance in local windows. The blooming threshold ex expected to degrade over time due to radiation damage, and thus must be monitored.
Required accuracy, constraints¶
TBW
Processing tools¶
TBW (Will likely be a part of OU-VIS PTC Processing Element)
Validation¶
Compare the saturation maps in flight with those obtained on ground. Over time, we expect a slow degradation (lowering) of the blooming threshold due to radiation damage.
Recovery¶
Repeat.
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Contact person¶
VIS instrument scientist