CALPRODUCT-NP-001: NISP-P Absolute Photometric Standards

Parent requirement

R-CAL-B-NP-3000
R-CAL-B-NP-3110
R-CAL-B-NP-3120

Scheduling

Once, during PV phase, with high spatial sampling.

Upon request during routine phase, with low spatial sampling, if unexplained discrepancies occur in photometry after processing.

Time-critical

PV phase: No.

Routine phase: Yes. The observations are used to assist with the investigation of discrepancies in the photometric data, and should be scheduled as soon as possible.

Dependencies

Objective

Obtain absolute flux standard measurements as a function of position for each NISP detector, therefore characterizing the entire optical path. The observations serve as an independent check of the global system response, as well as the impact of persistence and trap filling.

Fulfilled by

CALBLOCK-PV-002: NISP-P and VIS Absolute Photometric Standards

CALBLOCK-PV-001: Self Calibration (provides part of the information, random dithers)

CALBLOCK-F-001: Self Calibration (provides part of the information, random dithers)

Data volume

PV phase:

NISP: 3*16*16*3 * NP = 202752 MB

VIS: 256*VS = 115712 MB

Routine phase:

NISP: 2*4*16*3 * NP = 33792 MB

VIS: 64*VS = 28928 MB

Processing input

Ground Processing Input Data: All calibration products to run the standard science pipeline (BPM, darks, flat, nonlinearity, etc (?)), reference measurement of standard star, RSR curves (relative spectral response of the system (mirrors, optics, instrument)

Data Description:

PV phase:

NISP: 3*16*16*3 = 2304 photo-MACC images

VIS: 256 images (one VIS image at every dither point)

Routine phase:

NISP: 2*4*16*3 = 384 photo-MACC images

VIS: 64 images (one VIS image at every dither point)

Processing output

  • Mean and stdev of the photometric zeropoint (conversion factor) per detector

  • Plot of zeropoint as a function of position in the focal plane (with the detector grid overlaid)

  • Plot comparing the fluxes of the 1st, 2nd, and (PV phase only) 3rd exposures

Required accuracy, constraints

  • Photometric flux measurement / photometric conversion factor derived from each position are within 1.5% of the mean.

  • The flux measurements of the first and second exposure at a given dither must be the same within the combined uncertainties of the measurement and the persistence model.

  • Comparsion with expectations from the total system throughput, should be within TBD%

Processing tools

L1 science pipeline and absolute calibration pipeline, additional offline trend analysis of flux measurements

Validation

The map of absolute zeropoints should mainly reflect the quantum efficiencies at the respective pixel coordinates. Other effects, such as optical bandpass variations, are negligible.

The data can be used to directly test the top-level CalCD-A requirement R-CAL-A-NP-1000 (Post Calibration Relative Photometric Error < 1.5%), and G-CAL-A-NP-3000 (After all calibrations, the absolute photometric error of the NISP-P shall be < 5.0%). After all calibrations, the distribution of measured fluxes at the various detector positions, normalized by the intrinsic (true) fluxes, must have a width of not more than 1.5% of the flux (after correcting for photon noise), and the absolute fluxing should meet the CalCD-A goal.

Recovery

A failure of the validation is critical for the mission success and must be investigated with high priority. Possible causes are (non-exhaustive)

  • a severe short-coming in the data processing

  • incomplete understanding of the error budget

  • a significant change in hardware properties occurred (electronic, contamination, …)

Quality control parameters

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

Contact person

NISP-P calibration scientist