.. index:: Dispersion Solution; Planetary Nebula .. _calobs-block-f-nisp-wavelength-dispersion: **CALBLOCK-F-010:** NISP Wavelength Dispersion and VIS BFE ========================================================== .. include:: definitions.rst Observation configuration file ------------------------------ | :download:`ocf_CALBLOCK-F-010_BGS000-PN.csv ` | :download:`ocf_CALBLOCK-F-010_BGS000-SELFCAL.csv ` | :download:`ocf_CALBLOCK-F-010_PN-CENTERED.csv ` | :download:`ocf_CALBLOCK-F-010_RGS000-PN.csv ` | :download:`ocf_CALBLOCK-F-010_RGS000-ROT-PN.csv ` | :download:`ocf_CALBLOCK-F-010_RGS000-ROT-SELFCAL.csv ` | :download:`ocf_CALBLOCK-F-010_RGS000-SELFCAL.csv ` | :download:`ocf_CALBLOCK-F-010_RGS180-PN.csv ` | :download:`ocf_CALBLOCK-F-010_RGS180-ROT-PN.csv ` | :download:`ocf_CALBLOCK-F-010_RGS180-ROT-SELFCAL.csv ` | :download:`ocf_CALBLOCK-F-010_RGS180-SELFCAL.csv ` Scheduling ---------- Once, after 11-16 months of science operations and depending on PN visibility. Ideally falls into a time of future unallocated time periods. In case of failure, must be repeated at next possible opportunity. PN visibility will determine whether it can be included in a generic survey replanning effort, or whether a dedicated replanning effort is required. In case of parallel observations, EC-SURV should schedule tghe NISP component. Time-critical ------------- Within 11-16 months after the start of the routine survey. Objective --------- **NISP:** Observe a compact planetary nebula (PN) with strong emission lines as a function of position for each NISP detector, to obtain the wavelength dispersion solution. The dispersion solution is transfered to the Self-cal field to establish a set of standards that can be used to monitor for drifts. The Self-cal must be observed immediately after (or before) the PN observations, without grism wheel movements in between. **VIS:** Obtain flat-field pairs for :ref:`calobs-vis-bfe` Observations ------------ **NISP:** The PN is stepped across 5 positions on a detector, forming a quincunx pattern. At each position, spectroscopic observations are obtained. In total, 80 dither positions are realized for the 16 detectors. To establish the zeropoint of the wavelength solution, NISP-P images and therefore VIS images are also required. The **spectroscopic and imaging configurations must not be alternated** for these calibrations, as the grism will in general not come back exactly into the same position. The latter would render a self-consistent dispersion solution impossible. Therefore, once a grism is moved into the beam, all 80 dither positions must be completed, followed by a slew to the Self-cal field where spectra only are taken. The observing sequence is as follows: First, the ROS is executed four times, with the PN placed near the four corners of the FPA. Effectively, this forms a :math:`2\times2` grid around the PN. In this way, all subsequent NISP-S exposures can have their wavelength zeropoints determined, and an astrometric grid is established over the entire field. The NISP-S exposures taken during the ROS are discarded for purposes of wavelength calibration (since the grism wheel is exercised repeatedly). Second, a slew is made such that the PN falls on the 1st quincunx position on the 1st detector. The first grism is selected, and without further offsets two NISP-S exposures (for cosmics rejection) are taken. Then the PN is placed on all other remaining positions where two exposures are taken. Third, **following immediately** to avoid changes of the thermo-optical state, a slew is made to the Self-cal field, respecting :ref:`specific angle constraints `. The Self-cal field is covered by 2x2 pointings, at each of which two slightly dithered NISP-S exposures are taken (to cover detector gaps and counter cosmics), without moving the grism wheel. It is assumed that the Self-cal field has been observed before during PV phase, and therefore NISP-P and VIS reference frames are already in place. Once this has been done, the next grism is selected while still being at the Self-cal field, observing the 2x2 grid. Then a slew is made to the PN, repeating the spectroscopic observations as described above. If **P** and **S** refer to the PN and the Self-cal fields, respectively, and a **--** to a large slew, then the most efficient sequence to calibrate the grisms would be **P--SS--PP--SS--PP--S** **VIS:** In the initial ROS block, the ROS_D1 VIS variants are mostly NominalScience+ShortScience [NS+SS] with some [NS+Bias] interspersed (one per pointing, 4 total). The Short Science aid in VIS photometry and astrometry of the bright NISP target. The biases provide instrumental reference. While NISP takes the PN spectra pairs, VIS will take pairs of flats, and very short science exposures. The VIS pairs fit comfortably within the duration of the NISP spectra, and the NISP spectra are not affected by the VIS shutter movement. .. code-block:: python :caption: Wavelength calibration (involving a **P--SS--PP--SS--PP--S** pattern with 5 large slews). Note that RA/Dec coordinates for the 2x2 grid on the Self-cal field cannot be given, as these are launch dependent (field rotation). for PN near [upper left, upper right, lower right, lower left] corner of NISP FPA: "near" = PN should be 1' INSIDE the field-of-view in both detector dimensions "Observe ROS" ****** "select grism 1" "Slew to PN" for offset in 5*16 = 80 dither_offsets: "NISP observe 2x spectro-MACC without offsets" if position 1/5 on a detector: 2x VIS flat 10 kADU with LED1 if position 2/5 on a detector: 2x VIS flat 10 kADU with LED1 if position 3/5 on a detector: 2x VIS flat 10 kADU with LED4 if position 4/5 on a detector: 2x VIS flat 10 kADU with LED4 if position 5/5 on a detector: 2x VIS 2 second science exposure "Slew to Self-cal" for position in 2x2_grid_positions: "NISP observe spectro-MACC" "Offset 70x70 arcsec in x/y direction to cover gaps" "NISP observe spectro-MACC" "select grism 2" for position in 2x2_grid_positions: "NISP observe spectro-MACC" "Offset 70x70 arcsec in x/y direction to cover gaps" "NISP observe spectro-MACC" "Slew to PN" for offset in 5*16 = 80 dither_offsets: "NISP observe 2x spectro-MACC without offsets" if position 1/5 on a detector: 2x VIS flat 10 kADU with LED1 if position 2/5 on a detector: 2x VIS flat 10 kADU with LED1 if position 3/5 on a detector: 2x VIS flat 10 kADU with LED4 if position 4/5 on a detector: 2x VIS flat 10 kADU with LED4 if position 5/5 on a detector: 2x VIS 2 second science exposure ****** "Repeat the block within ****** for grisms 3+4, and its first half for grism 5." Fulfilling ---------- :ref:`calobs-nisp-spec-wavelength-dispersion-pn` :ref:`calobs-nisp-spec-wavelength-transfer` :ref:`calobs-vis-bfe` Targets and pointing constraints -------------------------------- .. _PN_angle_constraints_f: :command:`Pointing`: Straylight suppression as per MOCDA-SYS-003. Within this limit, the angles for the PN observations by NISP are unconstrained. The Self-cal visits can have the same AA as the PN observations, and excursions of up to :math:`0.5` are considered tolerable as long as the AA limit is not violated. The SAA does not need to be preserved when slewing from the PN to Selfcal. From a thermal point of view, VIS can tolerate angle excursions for up to two hours without suffering from PSF degradation, hence we do not expect changes to the optical distortion for NISP-S (EUCL-OXF-TN-8-008). .. csv-table:: **Compact Planetary Nebulae.** The units of the Pa-:math:`\beta` line fluxes are [erg/s/cm^2]. Crowding is defined as the number of sources brighter than Gaia Gmag<19 :math:`{\rm arcmin}^{-2}`. The radius refers to EE80 from HST imaging and slitless spectroscopy. :download:`CSV file ` :widths: 16, 10, 10, 12, 6, 10, 20 :file: tables/targets-PN.dat | .. csv-table:: **Visibility of selected, most promising PNe.** SMC-SMP-20 is strongly preferred. Ask before using any other. :download:`CSV file ` :widths: 14, 35, 35 :file: tables/PN_visibility.dat | .. csv-table:: **Self-cal field** (2x2 grid) :download:`CSV file ` :file: tables/targets-selfcal-center.dat Instrument configuration ------------------------ Instrument: Wide survey; special (grism only) Methodology / Uplink procedure ------------------------------ :command:`Entity`: VIS & NISP :command:`Commanding Method`: NISP: Observation, VIS: Science :command:`Dither Sequence`: ROS, and specialized sequences. The ROS is used for initial imaging of the PN field. The PN spectra are obtained using a specialized dither pattern. In the plots below, **the arrow heads** correspond to the non-dispersed wavelength at 1213 nm (red grisms) and 923 nm (blue grism), respectively. They very closely coincide with the position of the sources if an image was taken instead of a spectrum, and therefore define the dither patterns (linked below the figure). The arrows point in the direction of increasing wavelength. **The lines** show to the 1st order spectra of a continuum source. **The points** correspond the positions of the 0th orders. .. |RGS000_0| image:: ../images/RGS000_0_PN.png :scale: 33% .. |RGS000_-4| image:: ../images/RGS000_-4_PN.png :scale: 33% .. |RGS180_0| image:: ../images/RGS180_0_PN.png :scale: 33% .. |RGS180_+4| image:: ../images/RGS180_+4_PN.png :scale: 33% .. |BGS000| image:: ../images/BGS000_PN.png :scale: 33% +-------------+---------------+ | |RGS000_0| + |RGS000_-4| + | RGS000 + RGS000_rot + +-------------+---------------+ | |RGS180_0| + |RGS180_+4| + | RGS180 + RGS180_rot + +-------------+---------------+ | |BGS000| + + | BGS000 + + +-------------+---------------+ These links contain the dithers in the NISP Y_MOSAIC / Z_MOSAIC coordinate system, spanning all detectors in the focal plane, and in units of mm. **The tables are valid for both the unrotated as well as the rotated grism positions.** To fully preserve the 0th and 1st orders within individual detectors, we require a pointing accuracy of 100 pixel or 30 arcsec, well within the spacecraft's capabilities. :download:`RGS000 dither offset ` :download:`RGS180 dither offset ` :download:`BGS000 dither offset ` The Self-cal field is covered with a 2x2 grid, using grism only observations, as outlined in the description above. Inter-operability constraints ----------------------------- None In-orbit duration ----------------- :command:`In-orbit Duration`: 160.8 h 4.8 h for establishing the astrometric reference frame on a :math:`2\times2` grid (executing the ROS 4 times). ``2*80*573s + 80*170s = 29.2 h`` for calibrating a single grism: spectro-MACC mode, 2 exposures at each of the 80 dither positions. The typical dither offset for the quincunx pattern is 4 arcminutes, hence a field slew taking 170 s. 0.5 hours for a slew from the PN to the Self-cal field. ``2*4*573s + 4*60s + 3*200s = 1.5 h`` for the Self-cal field: Two spectro-MACC exposures separated by one diagonal dither (60 s) to cover the detector gaps, executed on a :math:`2\times2`, with 3 field slews (200 s) to reach the 4 grid points. In total ``4.8h + (29.2h+0.5h+1.5h)*5 = 160.8 h`` or 6.7 days for 5 grims. The VIS flat fields are entirely accommodated in the NISP spectra exposures, and do not drive the overall execution time. EC-SURV should schedule the NISP component in the RSD. Data volume ----------- Total: 667304 MB NISP-S: ``(80*2 + 4*2)*5*NS = 136920 MB`` for the PN and Self-cal NISP-S exposures NISP-P: ``3*4*4*NP = 2832 MB`` for the astrometric NISP-P exposures VIS: ``12*VS = 5424 MB`` for the VIS astrometric exposures VIS: ``4*VB = 1000 MB`` for the VIS instrument reference VIS: ``5*(128*700MB + 32*452MB) = 520320 MB`` for the flat fields and short science exposures Average data rate: 796 Gbit / 24h Processing input ---------------- :command:`Ground Processing Input Data`: All calibration products to run the standard science pipeline (BPM, darks, flat, nonlinearity etc), ground-based dispersion data/model. :command:`Data Description`: NISP: 890 spectro MACC images (10*16*5), 48 photo MACC images, VIS: 461 images Processing output ----------------- The dispersion solution as a function of detector position for all detectors and all grisms. A set of secondary wavelength calibrators in the Self-cal field. Required accuracy, constraints ------------------------------ Emission line centroids successfully extracted from all PN measurements Processing tools ---------------- VIS_ProcessField_Pipeline, Validation ---------- The new wavelength dispersion solution is compared against the solution from the PV phase. If the differentials are less than TBD (fraction of pixel) everywhere in the field of view, then the established solution remains unchanged. Recovery -------- If a change in solution is found, then the impact on the science must be evaluated. If the change is minor (i.e. using the old solution did not violate the requirements), then we could just update the dispersion solution with the new measurement. If a large discrepancy is found, then this would imply that a fraction of the science data (probably months) would need reprocessing, and perhaps a linear interpolation between the two solutions if such an interpolation can be derived. This is not expected and would warrant further investigation. In the worst case, the wavelength transfer observations must be repeated with higher cadence. Quality control parameters -------------------------- DataModel: ``_ Contact person -------------- NISP-S calibration scientist .. raw:: latex \clearpage