.. index:: PRNU (VIS), Brighter-fatter effect(VIS) .. _calobs-block-pv-vis-prnu-bfe: **CALBLOCK-PV-022:** VIS PRNU and Brighter-fatter Effect ======================================================== .. include:: definitions.rst Observation configuration file ------------------------------ | :download:`ocf_CALBLOCK-PV-022_BF-40000ADU.csv ` | :download:`ocf_CALBLOCK-PV-022_LOW1-1000ADU.csv ` | :download:`ocf_CALBLOCK-PV-022_LOW2-5000ADU.csv ` | :download:`ocf_CALBLOCK-PV-022_PRNU1-25000ADU.csv ` | :download:`ocf_CALBLOCK-PV-022_PRNU2-10000ADU.csv ` Scheduling ---------- Once, during PV phase. LEDs 5+6 can be split off and scheduled at a later time, at the end or shortly after PV. In case of failure, repeat at next possible opportunity. Time-critical ------------- No Dependencies ------------ VS-CU commissioned Objective --------- .. index:: PRNU (VIS) Obtain near-monochromatic flat fields using the 6 LEDs in VS-CU. They form the basis to correct the small-scale features and pixel response non-uniformity (PRNU) (:ref:`calobs-vis-prnu`), and the brighter-fatter effect (:ref:`calobs-vis-bfe`). LEDs 5 and 6 are not used during normal observations in routine phase. Hence they can be taken after PV, at a suitable time. The pseudo-code below is refactored accordingly. Observations ------------ * **PRNU:** Obtain pairwise flats with dithers between pairs, at fluences 10 (16 pairs), 25 (7 pairs), and 40 (5 pairs) kADU. Like this, a S/N of about 1000 per pixel per fluence is achieved, assuming a gain of 3.48 e-/ADU, and allowing for 10% variation in gain and flatfield illumination. The total S/N should be up to 1700 before masking cosmic rays and bright sources. * **BFE:** Obtain pairwise flat fields with dithers in between, with fluence 1, 5 and 10 kADU, and LED1 to LED4. Direct observations of a stellar field (Self-cal) are also required, because the effect in flat fields is increased by space charges. To neutralize AOCS wait times, and to accommodate antenna repointing, the following strategy provides flat field images for both PRNU and BFE calibration. The spacecraft must not dither or slew during VIS flat field exposures. A science exposure is required for each dither to enable object masking, and sky-background correction. .. code-block:: none :caption: **Flat-field pairs for PRNU and BFE calibration, part #1 (LEDs 1-4).** The integration time of the short science (SS) exposure is defined by the ROS (total of 95 s, including the 5.48 s for the shutter movements). Dithers are random in a 3' box. BIAS Repeat 10x: 2 flats LED_1 with fluence 1 kADU 2 flats LED_2 with fluence 1 kADU SS, dither 2 flats LED_3 with fluence 1 kADU 2 flats LED_4 with fluence 1 kADU SS, dither BIAS Repeat 10x: 2 flats LED_1 with fluence 5 kADU 2 flats LED_2 with fluence 5 kADU SS, dither 2 flats LED_3 with fluence 5 kADU 2 flats LED_4 with fluence 5 kADU SS, dither BIAS Repeat 16x: 2 flats LED_1 with fluence 10 kADU 2 flats LED_2 with fluence 10 kADU SS, dither 2 flats LED_3 with fluence 10 kADU 2 flats LED_4 with fluence 10 kADU SS, dither BIAS Repeat 7x: 2 flats LED_1 with fluence 25 kADU 2 flats LED_2 with fluence 25 kADU SS, dither 2 flats LED_3 with fluence 25 kADU 2 flats LED_4 with fluence 25 kADU SS, dither BIAS Repeat 5x: 2 flats LED_1 with fluence 40 kADU 2 flats LED_2 with fluence 40 kADU SS, dither 2 flats LED_3 with fluence 40 kADU 2 flats LED_4 with fluence 40 kADU SS, dither .. code-block:: none :caption: **Flat-field pairs for PRNU and BFE calibration, part #2 (LEDs 5+6).** BIAS Repeat 16x: 2 flats LED_5 with fluence 10 kADU 2 flats LED_6 with fluence 10 kADU SS, dither BIAS Repeat 7x: 2 flats LED_5 with fluence 25 kADU 2 flats LED_6 with fluence 25 kADU SS, dither Repeat 5x: 2 flats LED_5 with fluence 40 kADU 2 flats LED_6 with fluence 40 kADU SS, dither Fulfilling ---------- :ref:`calobs-vis-prnu` :ref:`calobs-vis-bfe` :ref:`calobs-vis-ptc` :ref:`calobs-vis-cti-eper` :ref:`calobs-vis-cosmetic-map` 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: VS-CU on Methodology / Uplink procedure ------------------------------ :command:`Entity`: VIS :command:`Commanding Method`: VIS: :command:`Dither Sequence`: Random dither offsets in a 3' box Inter-operability constraints ----------------------------- None. In-orbit duration ----------------- :command:`In-orbit Duration`: + **51.2 h + dither(x96)** [LED1234] + **15.6 h + dither(x28)** [LED56] Note that 66s of the CDPU processing time can be accommodated into the dither/slew duration. 1k ADU, 4 LEDs: 9.8 h + dither (x20) (CDPU processing buffer time for 1k ADU Flats: 295s) 5k ADU, 4 LEDs: 10.3 h + dither (x20) (CDPU processing buffer time for 5k ADU Flats: 320s) 10k ADU, 4 LEDs: 17.2 h + dither (x32) (CDPU processing buffer time for 10k ADU Flats: 340s) 25k ADU, 4 LEDs: 8.0 h + dither (x14) (CDPU processing buffer time for 25k ADU Flats: 370s) 40k ADU, 4 LEDs: 5.9 h + dither (x10) (CDPU processing buffer time for 40k ADU Flats: 380s) 10k, 25k, 40k ADU, 2 LEDs: 15.6 h + dither (x28) 2x(10+10+16+7+5) + 1x(16+7+5) = (96 + 28) = 124 dither slews: 124*66s = 2.3 h Data volume ----------- ``Total = 418,170 MB`` ``124*VS + 5*VB = 57,050 MB`` ``80*VF = 45,600 MB`` (``VF=570 MB``) ``80*VF = 54,400 MB`` (``VF=680 MB``) ``192*VF = 142,080 MB`` (``VF=740 MB``) ``84*VF = 68,040 MB`` (``VF=810 MB``) ``60*VF = 51,000 MB`` (``VF=850 MB``) Processing input ---------------- :command:`Ground Processing Input Data`: BPM, nonlinearity calibration correction, ground-based QE :command:`Data Description`: Total: 496 flats, 124 SS, 5 biases Processing output ----------------- Normalized combined flat fields for each LED, trend analysis Required accuracy, constraints ------------------------------ Expected flux levels within TBD%, stable within TBD%, spatial irradiance as expected (within requirement, ground-based measurements) Processing tools ---------------- Pipeline: VIS_MasterFlat_Pipeline PEs: VIS_BiasCorrection, VIS_PRNUCalibration Quality control parameters -------------------------- DataModel: ``_ Contact person -------------- VIS instrument scientist .. raw:: latex \clearpage