.. index:: VIS PSF model .. _calobs-block-f-vis-psfcalibration: **CALBLOCK-F-008:** VIS PSF Calibration and NISP photo nonlinearity =================================================================== .. include:: definitions.rst Observation configuration file ------------------------------ | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-008.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-012.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-020.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-040.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-080.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-150.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-200.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-350.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-450.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-550.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-750.csv ` | :download:`ocf_CALBLOCK-F-008_RAW-PHOTO-950.csv ` Scheduling ---------- Must schedule the :ref:`calobs-block-f-phase-diversity` PC-1ROS variant on the same target prior to beginning observations. This is needed to get the OU-PHZ data products for these fields. The cadence of the PSF calibration fields is tied to the reference survey design (RSD), in particular the major thermal disturbances due to large slew angles or attitude changes. The PSF calibration fields will be taken with a contemporary survey patch, using similar spacecraft attitude angles. A PSF calibration field is observed about every 2 to 6 weeks. Not all survey patches or windows can be linked to a PSF calibration field due to field selection, and insufficient time for thermal stabilisation. Due to the long replanning time and the involved thermal constraints, replanning would be a major effort. For the moment our strategy is therefore to simply skip the failed observation and wait for the next one. There is a risk that the PSF in the contemporary survey patch cannot be calibrated. Due to the long replanning time, that survey patch cannot be repeated immediately anyway and is therefore lost for immediate reobservation. **There are 12 different flavors due to NISP configurations.** They must be cycled consecutively in the RSD, in this order of fluences: 8, 20, 80, 200, 450, 550, 12, 40, 150, 350, 750, 950 e-/s The longer VIS component should be scheduled by EC-SURV. Dependencies ------------ F-012, F-015, and F-008 must be scheduled in this order as one set prior to the VIS PSF calibration (this CalBlock). Objective --------- **VIS:** Calibrate / validate the VIS PSF Model, using stars in the same magnitude range (17.5 < VIS < 21) as in the wide survey. The S/N must be 5x that of the wide survey. **NISP:** Take MACC(4,16,4) nonlinearity sequences in parallel. There are twelve different configurations, over which we cycle in a specific order (see :ref:`NL_fluence_cycling_order`). Observations ------------ First, observe one :ref:`calobs-block-f-phase-diversity` PC-ROS variant on the target. The PSF fields must be observed 100 times with an exposure time of 289 seconds. Ground-based SED information must be available for the sources in the field, from ground-based observations for fainter stars, and from Gaia for brighter stars. **Dithering:** At each dither point, one VIS Short Science (EXPTIME=289s) is executed. To avoid clustering of random dithers, we use points along a spiral. These produce a non-regular, yet fairly uniform distribution. In polar coordinates :math:`(\rho, \theta)`, and for a total of :math:`n` points, the position of point :math:`k` is given by: :math:`(\rho, \theta) = (scale * \sqrt{k} / 60, k* GoldenAngle)`, with :math:`scale = width / (2 \sqrt{n})` :math:`GoldenAngle = (3 - \sqrt{5}) * 180\;{\rm deg}` :math:`3' < width < 6'` (chosen by EC-SURV according to their constraints) NISP will take parallel ramps for :ref:`calobs-nisp-nonlinearity`. These are off-sky. NISP has no pointing constraints. The number of ramps and subsequent darks depends on fluence. The number of darks taken must not change the overall execution time, that is all variants must have the same duration, driven by the parallel VIS observations. A ramp with higher fluence (950e-/s) than in PV is included to calibrate the highest end of the dynamic range. .. _NL_fluence_cycling_order: .. code-block:: python :caption: **Structure of the observation block.** Slew to VIS PSF field NISP: Configure FWA = dark VIS: Repeat 100x: Take VIS science exposure with 289s duration Dither offset ------------ In parallel: No NISP wheel movements permitted at any time. Put NISP in "engineering RAW" mode Turn on LED "C" with a selected fluence. for detector in [1,...,16] (two at a time): if (fluence == 8 e-/s): 30 MACC(4,16,4) ramps if (fluence == 20 e-/s): 30 MACC(4,16,4) ramps if (fluence == 80 e-/s): 25 MACC(4,16,4) ramps if (fluence == 200 e-/s): 25 MACC(4,16,4) ramps if (fluence == 450 e-/s): 15 MACC(4,16,4) ramps if (fluence == 550 e-/s): 15 MACC(4,16,4) ramps if (fluence == 12 e-/s): 30 MACC(4,16,4) ramps if (fluence == 40 e-/s): 30 MACC(4,16,4) ramps if (fluence == 150 e-/s): 25 MACC(4,16,4) ramps if (fluence == 350 e-/s): 20 MACC(4,16,4) ramps if (fluence == 750 e-/s): 15 MACC(4,16,4) ramps if (fluence == 950 e-/s): 15 MACC(4,16,4) ramps Turn off LED "C" Put NISP in normal observation mode (no wheel movements) Take MACC(15,16,11) darks until VIS is finished. Fulfilling ---------- :ref:`calobs-vis-psfcalibration` :ref:`calobs-nisp-nonlinearity` Targets and pointing constraints -------------------------------- :command:`Pointing`: Straylight suppression as per MOCDA-SYS-003. Specific SAA and AA are required. **AA must be kept stable during the observation.** Small changes within an individual exposure due to orbit progression are permissible. The angles must match the typical spacecraft attitudes achieved during the contemporary survey patch, and are thus provided by EC-SURV. Suitable target fields have been selected near the ecliptic poles at a range of ecliptic longitudes to ensure year-round visibility. Selection criteria for the target fields are as follows: * Absence of V<10 mag stars in the field of view * Absence of V<4 mag stars near the field of view (scattered light on the focal plane) * Absence of bright and extended sources (e.g., objects in the NGC- and IC catalogs) * Optical polarization :math:`\ll0.01` and low galactic dust, as estimated from the Planck 353 GHz map * :math:`|{\rm ELAT}| \gtrsim 70^{\circ}`, to ensure constant visibility over consecutive weeks over the full SAA range The GAIA stellar density at the Self-cal field is sufficient for the VIS PSF algorithm to run successfully. However, the Self-cal field can only be observed at a fixed SAA of 90 degrees and is therefore insufficient to calibrate the PSF of all survey patches. .. csv-table:: **VIS PSF calibration fields** :download:`CSV file ` :widths: 20, 3, 3, 3, 3, 3, 3, 32 :file: tables/targets-vis-psfcalibration.dat | .. image:: ../images/vis_psf_fields_NEP.png :scale: 60% .. image:: ../images/vis_psf_fields_SEP.png :scale: 60% Figure: Northern ecliptic (left) and southern ecliptic (right) PSF fields. Instrument configuration ------------------------ Instrument: VIS: science. NISP: **Engineering Raw** for the nonlinearity measurement. NI-CU on (see table below), NI-FWA closed, NI-GWA RSG000 for the nonlinearity measurement. Uses **non-standard photo-MACC(15,16,11)** setting for the validation part. .. csv-table:: **LED "C" settings for nonlinearity measurements.** :download:`CSV file ` :widths: 20, 10, 10 :file: tables/NISP_LED-C_flux_LUT_nonlinearity.dat Methodology / Uplink procedure ------------------------------ :command:`Entity`: VIS, NISP :command:`Commanding Method`: VIS: science. NISP: Observation / engineering RAW :command:`Dither Sequence`: Special. Computed dither pattern as defined in `Observations`. Inter-operability constraints ----------------------------- NISP must not move any wheels during VIS operations. NISP must be configured before VIS starts taking data. In-orbit duration ----------------- :command:`In-orbit Duration`: 15 h Data volume ----------- One :ref:`calobs-block-f-phase-diversity` PC-ROS variant ``100*VS = 45200 MB`` ``8000 to 16000 MB`` depending on the number of ramps per variant Processing input ---------------- :command:`Ground Processing Input Data`: :command:`Data Description`: Recovery -------- Cannot be recovered. Continue with the survey plan. Quality control parameters -------------------------- DataModel: ``_ .. raw:: latex \clearpage