.. index:: Nonlinearity (VIS) .. _calobs-block-rec-vis-nonlinearity-flat: **CALBLOCK-REC-002:** VIS Flat Nonlinearity =========================================== .. include:: definitions.rst Observation configuration file ------------------------------ | :download:`ocf_REC-002.csv ` Scheduling ---------- Execute once after a full decontamination, after thermal stability of the VI-CU and VI-FPA have been reached (<0.1 K/h). Time-critical ------------- No. Dependencies ------------ VI-CU commissioned Objective --------- Radiation damage may slightly alter voltages in the VIS electronics, changing the :ref:`VIS nonlinearity ` as well as the PSF model. The VIS nonlinearity must be monitored continuously. This ``CalBlock`` obtains the nonlinearity estimate from flat fields, complementing :ref:`calobs-block-pv-vis-nonlinearity-onsky`. Observations ------------ **Parallel schedule:** :ref:`calobs-block-pv-nisp-LED` as necessary; this ``CalBlock`` is driven by VIS. Accurate Bias subtraction is essential for the low fluence settings. The intermediate flats with 2000 ms duration are for the control of any LED drifts. With windowed flats, the 120 lines of overscan provide added value for CTI as well as a possible CTI correction to the measured signal. The first 1086 lines are flushed with a ``TOI=143``:math:`\,\mu{\rm s}`, the rest of the image is read out normally. The trail (if any) can be compared with the nominal EPER trail. For offset construction, the parallel overscan of the serial overscan should be used at higher signal levels. Therefore, increasing the parallel overscan may also be useful. The Short Science (SS) frames are necessary to remove astronomical objects from the FLAT images. They will be scaled to match the FLAT exposure time. .. code-block:: python :caption: VIS flat field nonlinearity sequence, with interspersed exposures of 2000ms integration time to control LED drifts. SS refers to a short science exposure. Times are in milliseconds. BIAS settings: in full frame (at the top of the sequence) in windowed mode, VSTART=1086 (0x043E), VEND=2186 (0x088A) (the latter includes 120 overscan lines) Flat setting: LED3 with 3 mA Use windowed mode, VSTART=1086 (0x043E), VEND=2186 (0x088A) (the latter includes 120 overscan lines) EXPTIME should be 500ms up to 200ms LED_DELAY, otherwise add 500~2500s to LED_DELAY for EXPTIME SS setting: Use windowed mode, VSTART=1086 (0x043E), VEND=2186 (0x088A) (the latter includes 120 overscan lines) EXPTIME should match what is used in the FLAT (there should be two different EXPTIMEs per dither) Full-frame BIAS in windowed mode: BIAS, SS, 2000, 1, 2, 3, 4, SS, dither in windowed mode: BIAS, SS, 2000, 5, 6, 7, 10, SS, dither in windowed mode: BIAS, SS, 2000, 20, 32, 40, 50, SS, dither in windowed mode: BIAS, SS, 2000, 100, 200, 300, 400, SS, dither in windowed mode: BIAS, SS, 2000, 500, 750, 1000, 1500, SS, dither in windowed mode: BIAS, SS, 2000, 3000, 3750, 5000, SS, dither in windowed mode: BIAS, SS, 2000, 6000, 6500, 7000, SS, dither in windowed mode: BIAS, SS, 2000, 8000, 2000, SS, BIAS, dither Full-frame BIAS in windowed mode: BIAS, SS, 2000, 1, 2, 3, 4, SS, dither in windowed mode: BIAS, SS, 2000, 5, 8, 9, 12, SS, dither in windowed mode: BIAS, SS, 2000, 16, 24, 28, 32, SS, dither in windowed mode: BIAS, SS, 2000, 64, 86, 128, 150, SS, dither in windowed mode: BIAS, SS, 2000, 400, 600, 750, 1000, SS, dither in windowed mode: BIAS, SS, 2000, 1250, 2500, 3500, SS, dither in windowed mode: BIAS, SS, 2000, 4000, 4500, 5500, SS, dither in windowed mode: BIAS, SS, 2000, 7500, 8500, 2000, SS, BIAS, dither Note: The NL calibration at low fluence can be refined if the same sequences can be run at a different LED current (via better understanding of the exact LED actuation duration). Such a **variant sequence** is defined in a separate CALBLOCK (TBW) to be run after PV, if necessary. Fulfilling ---------- :ref:`calobs-vis-nonlinearity` Targets and pointing constraints -------------------------------- :command:`Pointing`: Straylight suppression as per MOCDA-SYS-003. .. csv-table:: SELFCAL-FAINT :download:`CSV file ` :widths: 15, 8, 8 :file: tables/targets-selfcal-faint.dat Instrument configuration ------------------------ Instrument: VI-CU LED3 on Methodology / Uplink procedure ------------------------------ :command:`Entity`: VIS :command:`Commanding Method`: :command:`Dither Sequence`: Random dithers in a 3' box Inter-operability constraints ----------------------------- NISP mechanisms must not move while VIS observes on sky. In-orbit duration ----------------- :command:`In-orbit Duration`: 6.4 h + dither (x16) Note that 66s of CDPU processing time has been absorbed into each dither/slew. Data volume ----------- ``Total = 31786 MB`` | ``VB = 2*250 MB = 500MB`` for the full-frame Bias | ``18*VB(117MB) + 32*VS(240MB) = 9786 MB`` for the Bias and SS (windowed) | ``27*VF (200 MB) = 5400 MB`` for 27 flats below 0.6 kADU | ``14*VF (300 MB) = 4200 MB`` for 14 flats below 6 kADU | ``18*VF (350 MB) = 6300 MB`` for 18 flats with 13 kADU (2000 ms interspersed images) | ``14*VF (400 MB) = 5600 MB`` for 14 flats higher than 30 kADU Processing input ---------------- :command:`Ground Processing Input Data`: None :command:`Data Description`: 2 full-frame Biases (LE1), 18 windowed Biases (LE1), 32 windowed SS (LE1+CR removal), 73 windowed flats (LE1) Processing tools ---------------- Cosmic ray removal of the SS images. Quality control parameters -------------------------- DataModel: ``_ Contact person -------------- VIS instrument scientist .. raw:: latex \clearpage