CALPRODUCT-NI-011: NISP Nonlinearity Verification¶
Parent requirement¶
Scheduling¶
During PV phase, then once every 6 months.
Time-critical¶
No
Objective¶
Validate the ground-based nonlinearity measurements.
On ground we have tested 5 different flux levels of 16, 30, 70, 110, 150 e-/s, obtaining spectro-MACC ramps and saving each of the 15 group images. The ramps for the three lowest fluxes were repeated 30 times, the two highest ramps are repeated 10 times to obtain sufficient S/N.
We also need 5 different flux levels for the photo-MACC mode to construct the final nonlinearity lookup tables.
Fulfilled by¶
Data volume¶
535040 MB
spectro-MACC ramp: 16 bit * 2048*2048 pixel * 16 detectors * 15 groups = 1920 MB (uncompressed)
photo-MACC ramp: 16 bit * 2048*2048 pixel * 16 detectors * 4 groups = 512 MB (uncompressed)
110 ramps for spectro-MACC and photo-MACC each.
Processing input¶
Ground Processing Input Data: BPM
Data Description: 4800 group images (single detector). There might be additional dark images accompanying these data.
Processing output¶
Linearity correction for each pixel. Comparison to ground characterization. Comparison of field star fluxes measured with photo-MACC and spectro-MACC mode after full calibration.
Required accuracy, constraints¶
Must be able to compare the in-flight nonlinearity correction to the ground characterization.
Processing tools¶
L1 nonlinearity pipeline, offline analysis likely
Validation¶
The nonlinearity behavior should be indistinguishable from that measured on ground, otherwise an update of the lookup tables is required.
Observe the Self-cal field with spectro-MACC mode, using the GWA in open position and the FWA set to the Y, J and H filters. Like this, we will observe the same sources at different fluences, and can directly check whether the nonlinearity correction is adequate.
Note that spectro-MACC has a different non-linearity solution than photo-MACC. It is currently not clear how any discrepancies occurring during validation can be used to improve either nonlinearity model.
Recovery¶
Either the bright, faint, or both nonlinear regimes must be repeated. The faint end is very expensive and requires about 11 days.
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Contact person¶
NISP-P calibration scientist