.. index:: Phase diversity; Calibration observations .. _calobs-block-pv-phase-diversity: **CALBLOCK-PV-008:** Phase Diversity Calibration ================================================ .. include:: definitions.rst Observation configuration file ------------------------------ | :download:`ocf_CALBLOCK-PV-008_EXTRA-FOCAL-PDC.csv ` | :download:`ocf_CALBLOCK-PV-008_EXTRA-FOCAL-SM.csv ` | :download:`ocf_CALBLOCK-PV-008_IN-FOCUS-PDC.csv ` | :download:`ocf_CALBLOCK-PV-008_INTRA-FOCAL-PDC.csv ` | :download:`ocf_CALBLOCK-PV-008_INTRA-FOCAL-SM.csv ` | :download:`ocf_CALBLOCK-PV-008_NL-PDC.csv ` | :download:`ocf_CALBLOCK-PV-008_TF-EXTRA-FOCAL.csv ` | :download:`ocf_CALBLOCK-PV-008_TF-INTRA-FOCAL.csv ` Scheduling ---------- Once, during PV phase. The remainder of the PDC observations is executed immediately after PV phase, in :ref:`calobs-block-f-phase-diversity`. In case of failure, repeat as soon as possible without change of the telescope's thermal equilibrium. Otherwise, we need another thermal stabilization phase. Time-critical ------------- Yes. Must be executed after :ref:`calobs-block-pv-vis-thermal-timescale`, without further attitude changes. Objective --------- These observations demonstrate the technical feasibility of phase diversity calibration (PDC), and already obtain usable data. PDC is used to determine the VIS wavefront error for PSF modeling, as a function of various thermal states depending on AA and SAA. A stellar fields will be observed with the telescope being both in a defocused and a focused state, in thermal equilibrium. Only one PDC field is observed during PV phase, obtaining data for one thermal state. The remainder of the PDC fields is scheduled immediately after PV phase. Observations ------------ **Defined thermal pulse:** The thermal relaxation timescale is not accurately known prior to launch, and is measured through :ref:`calobs-block-pv-vis-thermal-timescale`. This requires a thermal pulse, by thermally stabilizing Euclid at :math:`{\rm AA}=-8.5` for several days (e.g. :ref:`calobs-block-pv-absolute-standards-imaging`, then switching to :math:`{\rm AA}=-3.5` for :ref:`calobs-block-pv-vis-thermal-timescale`. **NISP activities during PDC:** NISP must not observe during PDC observations, to not disturb VIS with wheel movements, and due to bandwidth limitations. **Photometric classification:** 8 ROS_D1 are executed at each PDC field and AA orientation to improve star/galaxy separation. SOC may choose to execute a larger number of ROS_D1 if e.g. part of thermal stabilisation. **Thermal stabilization:** This is defined separately as :ref:`calobs-block-pv-vis-thermal-timescale`. **Instruments must not be idling during this time, and should stay as close as possible to normal operations, to maintain a typical thermal balance in the PLM.** Parallel NISP calibrations can occur that do not require a specific pointing, such as :ref:`calobs-block-pv-nisp-darks` :ref:`calobs-block-pv-nisp-ipc` :ref:`calobs-block-pv-nisp-nonlinearity` :ref:`calobs-block-pv-nisp-LED` :ref:`calobs-block-pv-nisp-persistence` (nominal persistence calibration, one week after :ref:`calobs-block-pv-nisp-LED`) :ref:`calobs-block-pv-nisp-persistence` (check 1) :ref:`calobs-vis-shuttermap` **Shutter map:** PDC requires an updated shutter map for the defocused telescope. It must be measured from 10 pairs of 20s and 5s long science exposures (not counting the shutter opening/closing time of 6s). The pairs are taken at the same dither position, with dither offsets between pairs and located on a 100" diameter circle (minimum RTM dither offset) as for the defocused observations. **PDC:** The telescope must have been in the same SAA/AA position for 5 to 7 days to reach thermal equilibrium. During PV, one SAA/AA position is realised (at the NEP). * Relative tracking mode (RTM) must be used for all PDC observations, as we can then control the PEC selection. Improved absolute pointing accuracy with absolute tracking mode (ATM) is not required. * SAA/AA position 1: Extrafocal, intrafocal, focal, including shutter maps for the extrafocal and intrafocal states, and one pass of :ref:`calobs-block-pv-vis-nonlinearity-onsky`. Executed at the :ref:`calobs-block-pv-selfcal` field. .. _figure_PDC_baseline: .. figure:: ../images/PDC_baseline_1.png :scale: 66 :align: left :class: with-border Baseline for the first PDC observation during PV. Green areas show thermal stabilisation times. Yellow fields are the actual PDC observations. Red fields show changes in attitude or pointing. Fulfilling ---------- :ref:`calobs-vis-phase-diversity` Depending on what is scheduled during the thermal stabilization, e.g. :ref:`calobs-nisp-darks` :ref:`calobs-nisp-ipc` :ref:`calobs-nisp-led-flats` :ref:`calobs-nisp-nonlinearity` :ref:`calobs-nisp-persistence` :ref:`calobs-vis-shuttermap` Targets and pointing constraints -------------------------------- :command:`Pointing`: Prior to the thermal stabilization period, we maintain :math:`{\rm AA}=-8.5` ideally for 4-7 days to create a different thermal state. During PDC, including thermal stabilization, **SAA and AA must be kept stable.** Small changes within an individual exposure due to orbit progression are permissible. The SAA is constrained by launch-time. In case of an "attidue hold mode" or AHM, the spacecraft must maintain its current attitude to not destroy the thermal equilibium. .. csv-table:: **VIS Phase Diversity fields.** :download:`CSV file ` :widths: 20, 6, 6, 6, 6, 6, 6, 30 :file: tables/targets-vis-phase-diversity.dat Instrument configuration ------------------------ Instrument: Special. Requires M2M movements (defocusing). RTM mode. Methodology / Uplink procedure ------------------------------ :command:`Entity`: VIS :command:`Commanding Method`: VIS: Science :command:`Dither Sequence`: 150 dithers in a 100" diameter circular pattern for PDC. Same for the 10 dithers of the shutter maps. The 8 ROS_D1 dithers are also dithered on the same 100" diameter circle, evenly spaced, so that NISP coverage is maximised for the full area. Inter-operability constraints ----------------------------- VI-CU off In-orbit duration ----------------- :command:`In-orbit Duration`: 57 h (without thermal stabilisation time) 17 days with preceeding thermal pulse and thermal stabilisation. Data volume ----------- One SAA/AA point, including unrelated in-line calibrations: about 2600000 MB Processing input ---------------- :command:`Ground Processing Input Data`: TBD :command:`Data Description`: TBD Processing method ----------------- TBD Processing output ----------------- PSF model Required accuracy, constraints ------------------------------ TBD Validation ---------- VIS: The analysis of the phase diversity data is a substantial manual off-line task done by OU-SHE, and the validation / success criteria are not available at this time. Results are expected only once we are well into the routine phase observations, at which point a phase diversity campaign will not be repeated lightly. For the NISP observations, see the respective ``CalProducts``. Quality control parameters -------------------------- DataModel: ``_ Contact person -------------- Calibration Lead .. raw:: latex \clearpage