.. index:: LED Flat (NISP) .. _calobs-nisp-led-flats: **CALPRODUCT-NI-010:** NISP LED Flats ===================================== .. include:: definitions.rst Parent requirement ------------------ | `R-CAL-B-NP-1110 `_ | `R-CAL-B-NP-1120 `_ | `R-CAL-B-NP-2110 `_ | `R-CAL-B-NP-2120 `_ Scheduling ---------- PV phase (10, 20, 30, 40, 50 kADU) Monthly (30 kADU fluence, only) Time-critical ------------- No Objective --------- Obtain NISP LED flats for all 5 LEDs. They form the basis to correct the small-scale features and pixel-to-pixel response non-uniformity (PRNU) in the photometric and spectroscopic data (:ref:`calobs-nisp-phot-small-scale-flats` and :ref:`calobs-nisp-spec-small-scale-flats`), and to characterize :ref:`calobs-nisp-bfe`. In flight, we will probably need less fluences on a monthly basis. During PV phase, 5 different fluences will be taken to also characterize the brighter-fatter effect. Fulfilled by ------------ :ref:`calobs-block-pv-nisp-LED` :ref:`calobs-block-f-visNL-nispLED` Data volume ----------- ``750*NP (flats) + 30*NS (spectro-MACC darks) = 70380 MB``. The darks are not needed for the analysis. Processing input ---------------- :command:`Ground Processing Input Data`: BPM, photo-MACC master dark, nonlinearity calibration correction, ground-based QE, ground-based fine wavelength grid flats :command:`Data Description`: 750 photo-MACC images (5 LEDs, 5 fluences, 30 exposures per setting) Processing method ----------------- Compute the mean (or median) flux level per exposure and detector. Identify the n-th exposure, after which the flux does not change significantly anymore (burn-in achieved). Perform a median-combination using outlier rejection (masking of cosmics) for each LED fluence setting. Processing output ----------------- Normalized combined flat fields for each LED, trend analysis. Processing tools ---------------- L1 small scale flat pipeline, trending statistics, offline analysis for trapping/de-trapping, persistence, Validation ---------- The LED flats must not have structures on scales of 100 pixels or below .. _figure_nicu_asd: .. figure:: ../images/NICU_asd.png :scale: 100 :align: left Amplitude spectral density of the NI-CU verification model. The spectrum is noise-dominated at smallest spatial scales, but other than that well below the requirement. The NI-CU in-flight LED flats must fulfil this requirement as well. The fluence should be within 5 kADU of the targeted values, and the spatial irradiance as expected (approximately 10% drop-off from the center to the field corner). Recovery -------- If the requirement on small-scale flatness is violated, then the root cause must be identified. Assuming the initial checks during PV-phase fulfil the requirement, then a later violation could indicate e.g. build-up of ice on the detector, warranting a decontamination. Growing ice deposits would also be detected by monitoring photometric zeropoints. A violation of the small-scale LED flatness requirement is a serious issue and must be investigated. Quality control parameters -------------------------- DataModel: ``_ Contact person -------------- NISP-P calibration scientist .. raw:: latex \clearpage