.. index:: CTI Charge Injection .. _calobs-block-pv-vis-cti-charge-injection: **CALBLOCK-PV-028:** VIS CTI Charge Injection ============================================= .. include:: definitions.rst Parent requirement ------------------ | `R-CAL-B-VS-4355 `_ | `R-CAL-B-VS-4356 `_ Observation configuration file ------------------------------ | :download:`ocf_CALBLOCK-PV-028_CI-ROS.csv ` | :download:`ocf_CALBLOCK-PV-028_IG1-SCAN.csv ` | :download:`ocf_CALBLOCK-PV-028_CI-DARKS-AB.csv ` | :download:`ocf_CALBLOCK-PV-028_CI-DARKS-C.csv ` Scheduling ---------- Once, at the beginning of PV phase. Must be scheduled together with :ref:`calobs-block-pv-vis-cti-timingsequence`. In case of failure, repeat as soon as possible. This calibration should be taken when radiation damage to the detectors is still very low. - **ROS variant:** Keep the first ROS (x6 block repetition) sequence as early as possible, to minimise radiation damage for the best estimate of final settings. - **IG1-SCAN variant:** Run all x6 block repetition as early in PV as possible (similar to ROS variant). The last two of the IG1-SCAN series is meant for direct comparison with the ROS variant, and can be omitted if the IG1-SCAN is run immediately after the ROS variant. - **CI-DARKS-AB variant:** (AB refers to the two CI configurations A and B) Run once for each particular SAA/AA spacecraft attitude of interest. - **CI-DARKS-C variant:** Run once for two SAA/AA spacecraft attitudes, at high and low straylights. Time-critical ------------- Must be scheduled as early as possible in PV, when radiation damage is still low, to minimize CTI in CCDs when observations are taken. Must be scheduled together with :ref:`calobs-block-pv-vis-cti-timingsequence`. Dependencies ------------ None Objective --------- - **ROS and IG1-SCAN variants:** Characterize the highest levels of charge injection that are possible, which do not lead to failed charge injections in a subset of CCD's, by iterating over the IG1 and IG2 parameters of the charge injection in step sizes of IG1 and IG2 - IG1 of 0.05V, over the range IG1 = 3.25 -- 4.25V and IG2-IG1 = 2.75 -- 1.75V. Create a reference master charge injection line (CIL) pattern dataset which will be used to define what charge injections look like before CTI due to clocking; i.e., to build a pre-CTI/post-launch template. Characterize the temporal consistency of charge injection data (e.g. how much does the charge injection pattern change for two independent datasets?). This includes characterizing the charge injection column non-uniformity. Produce the initial CTI model used to correct CTI in images taken during PV when necessary. - **CI-DARKS-AB variant:** In Charge Injection images, it is the CI=OFF region where we expect the charge transfer inefficiency signal to yield measureable signal for CTI modeling and characterization. However, the CCD sees straylight even in the closed-shutter position, and also bias-level perturbations from other causes. The following configurations A, B, and C have been designed specifically to flush out the relation of the multiple sources of contamination, so that we can confidently isolate the desired CTI signal. These observations provide verification of straylight signal reconstruction in Charge Injection images. The reconstruction will be derived from a standard Dark image with the same straylight attitude. These observations will (in order of importance): (a) diagnose the source of the extra background over that seen in TVAC: how much is stray light, vs how much is electronic. (b) model the spatial frequencies on which stray light varies in a CI frame, in both x and y. (c) parameterise an expectation for the stray light patterns across the range of Alpha Angles (AAs) that will be used during the survey. Point (a) requires Dark+CI-Dark pairs at at least 3 stray light levels; ideally, 4 or 5 would be enough to look for and flag nonlinear surprises. (b) could be done with an exposure at AA>-2 where the stray light S/N is high. (c) would need 3 exposures at different values of AA<-2. - **CI-DARKS-C variant:** Additionally, we test for the root cause of a gradient in the CIL OFF regions, seen in some quadrants. It is uncertain whether this is a change in Bias offset, caused by the change in IG1/IG2 voltage settings. To model the effect in real CIL data, we need to know whether to split the CIL OFF regions, or treat them the same. Configuration C (see below) splits the image region into before and after the charge-injected region with wider "CI=OFF" regions, to see whether the setting of the IG1/IG2 voltages would perturb the no-charge-injection regions. Observations ------------ - **ROS variant:** The ROS variant is defined in :ref:`calobs-vis-cti-cil` as the charge injection data which are to be taken as part of the ROS. They are a seuqnce of 32 charge injection images (each with a different injection normalization and pattern). In the PV phase, 6 observations of every one of these 32 images are to be taken (6 observations are required to remove cosmic rays when characterizing the injection). One BIAS is interleaved every 8 CI. .. code-block:: none :caption: ROS variant execution sequence. Repeat 6x: BIAS, ROS-01, ROS-02, ROS-03, ROS-04, dither; ROS-05, ROS-06, ROS-07, ROS-08, dither BIAS, ROS-09, ROS-10, ROS-11, ROS-12, dither; ROS-13, ROS-14, ROS-15, ROS-16, dither BIAS, ROS-17, ROS-18, ROS-19, ROS-20, dither; ROS-21, ROS-22, ROS-23, ROS-24, dither BIAS, ROS-25, ROS-26, ROS-27, ROS-28, dither; ROS-29, ROS-30, ROS-31, ROS-32, dither - **IG1-SCAN variant:** The IG1-SCAN variant is taken to characterize the performance of the charge injection at the highest normalization, as defined below. This variant should be executed by a multiple of 6 times. One BIAS is interleaved every 6 CI. The last two (numbers 43 and 44) are acquired as a means of comparison to the ROS variant. Constant CIL parameters (PV): * Pattern = CIR3 * CHG_INJ_ON = 420 * CHG_INJ_OFF = 100 * VSTART_CHG_INJ = 16 * VEND_CHG_INJ = 2066 * VSTART = 0 * VEND = 2086 * :math:`30\mu{\rm s}` DWELL (CHINJ_RoDly) = ON * IG2 = 6V .. csv-table:: **Variable charge injection data (PV).** :download:`CSV file ` :file: tables/cti_pv.dat .. code-block:: none :caption: IG1-SCAN variant execution sequence. Repeat 6x: BIAS, IG1-01, IG1-02, IG1-03, dither; IG1-04, IG1-05, IG1-06, dither BIAS, IG1-07, IG1-08, IG1-09, dither; IG1-10, IG1-11, IG1-12, dither BIAS, IG1-13, IG1-14, IG1-15, dither; IG1-16, IG1-17, IG1-18, dither BIAS, IG1-19, IG1-20, IG1-21, dither; IG1-22, IG1-23, IG1-24, dither BIAS, IG1-25, IG1-26, IG1-27, dither; IG1-28, IG1-29, IG1-30, dither BIAS, IG1-31, IG1-32, IG1-33, dither; IG1-34, IG1-35, IG1-36, dither BIAS, IG1-37, IG1-38, IG1-39, dither; IG1-40, IG1-41, IG1-42, dither BIAS, IG1-43, IG1-44, dither - **CI-DARKS-AB variant:** Observations of simultaneous Dark and CI-Dark exposures are taken at 6 different spacecraft attitudes: Solar Aspect Angle (SAA) = 90 degrees and AA = [-7.0, -5.5, -2.5, -1.5, 0.0] degrees. The AA=0 will be useful because it should incontrovertibly have a stray light signal that is bright enough to detect and model. AA=-7.0 (with SAA=90 degrees) anticipates an unavoidable straylight level nominally seen during the ROS wide-survey calibration cycle. Three AAs (or straylight levels) is important because the key measurement is a plot of CI residual level vs stray light level. If that is linear, everything is caused by stray light; if linear plus a floor, there is an additional constant electronic term. It is more likely the latter is the case, based on the analysis so far. The latter has 3 free parameters - so at least 3 data points at 3 different AAs to constrain it; 4 or 5 data points (AAs) would be desirble to check that the model has no additional complexity. While the parameters DAC_IG1, DAC_IG2, and ID_DELAY become irrelevant when no charges are injected, the timing parameters (ID_DELAY, TOI_CHG_INJ, and CHINJ_RoDly) do affect the CI-Dark outcome. In this CALBLOCK, only the CHINJ_RoDly variants exists, corresponding to 2 different CI parameter configurations: A and B. Common CIL parameters for configurations A and B: * EXPTIME = 1 ms * DAC_IDL = 10.5 V * ID_WIDTH = 60 µs * CHG_INJ_ON = 0 * CHG_INJ_OFF = 2066 * VSTART_CHG_INJ = 16 * VEND_CHG_INJ = 2066 * VSTART = 0 * VEND = 2086 * DAC_IG1 = 4.75 V * DAC_IG2 = 6 V * ID_DELAY = 1500 µs * TOI_CHG_INJ = 1000 µs CIL timing parameters for configurations A and B: * 30 µs DWELL (CHINJ_RoDly) = ON (== Configuration A) * 30 µs DWELL (CHINJ_RoDly) = OFF (== Configuration B) The following pseudo-code describes the science acquisitions for the CI-DARKS-AB variant: At each pointing, take a Bias, 2x Darks, and 4x charge injections (CI) frames with no charge injected ("CI-Dark"). The nominal Dark exposures are integrated for 325 seconds. .. code-block:: none :caption: CI-DARKS-AB variant, executing a Charge-Injection Dark (CIDark) sequence. while SAA = 90 degrees: for each AA = [-7.0, -5.5, -2.5, -1.5, 0.0]: BIAS, DARK, DARK, CIDark-A, CIDark-A, CIDark-A, CIDark-A dither BIAS, DARK, DARK, CIDark-B, CIDark-B, CIDark-B, CIDark-B dither - **CI-DARKS-C variant:** For Configuration C, the CIL parameters are the same as configurations A and B, except for the following: * CHG_INJ_ON = 50 * CHG_INJ_OFF = 743 * VSTART_CHG_INJ = 500 * 30 µs DWELL (CHINJ_RoDly) = ON This adds an extra pattern with 200 ON rows in the middle of the image, at nominal readout speed. .. code-block:: none :caption: CI-DARKS-C variant, executing a Charge-Injection Dark (CIDark) sequence. while SAA = 90 degrees: for each AA = [-5.5, 0.0]: BIAS, DARK, DARK, CIDark-C, CIDark-C, CIDark-C, CIDark-C dither Fulfilling ---------- :ref:`calobs-vis-cti-cil` Targets and pointing constraints -------------------------------- :command:`Pointing`: Straylight suppression as per MOCDA-SYS-003 for **ROS and IG1-SCAN variants**. :command:`Pointing`: Straylight variability for **CI-DARKS-AB and CI-DARKS-C variants**: :math:`{\rm SAA} = 90` and :math:`{\rm AA} = [-7.0, -5.5, -2.5, -1.5, 0.0]`. No specific target required. Instrument configuration ------------------------ Instrument: Wide survey Methodology / Uplink procedure ------------------------------ :command:`Entity`: VIS :command:`Commanding Method`: None :command:`Dither Sequence`: None Inter-operability constraints ----------------------------- None In-orbit duration ----------------- :command:`In-orbit Duration`: 63.4 h + dither (x150) [all CTI-Charge_Injection variants] - 19.4 h + dither (x48) [6x repetition of ROS block] - 35.1 h + dither (x90) [6x repetition of IG1-SCAN block] - 7.4 h + dither (x10) [5x s/c attitudes of 2x configurations]] - 1.5 h + dither (x2) [2x s/c attitudes of 1x configurations]] ROS Variant: 12,063s x 6 = 20.1 h (does not include dither) IG1-Scan Variant: 20,155s x 6 = 35.1 h (does not include dither) CI-DARKS-AB Variant: 2659s x 2 x 5 = 7.4 h (does not include dither) CI-DARKS-C Variant: 2659s x 2 = 1.5 h (does not include dither) Note that 66s of the CDPU processing time can be accommodated into the dither/slew duration. Data volume ----------- ROS (from S/C TVac data): ``14,500MB * 6 = 87,000 MB`` IG1-Scan (estimate): ``600MB * 44 * 6 = 158,400 MB`` BIAS: ``84*B = 21,000 MB`` DARK: ``24*D = 7,752 MB`` CI-DARK (charge injection frames without any charge injected, similar in size to a DARK): ``48*D = 15,504 MB`` Processing input ---------------- :command:`Ground Processing Input Data`: :command:`Data Description`: 456 Charge Injection images (= 32*6 + 44*6) 84 BIAS images (=4*6 + 8*6 + 2*5 + 2*1) 24 DARK images (=2*2*5 + 2*2*1) 48 Charge Injection Dark images (=4*2*5 + 4*2*1) Processing method ----------------- Binning, Cosmic Ray Flagging, CTI correction tools in VIS_CTI PE. Processing output ----------------- Master Charge Injection Non-uniformity Pattern. Statistics on Charge Injection temporal consistency. Initial CTI model. Required accuracy, constraints ------------------------------ | `R-CAL-B-VS-4354 `_ | `R-CAL-B-VS-4355 `_ | `R-CAL-B-VS-4356 `_ | `R-CAL-B-VS-4358 `_ Processing tools ---------------- VIS_CTI PE Validation ---------- * Check that the median injected charge level is within 5% of the value expected from ground testing. * Check that faux-parallel CTI trails are present for IG1 / IG2 settings expected from ground testing. * Flag any column of charge injection which does not have a measurement due to a cosmic ray hit in every one of the 6 datasets with the same charge injection parameters. For any that fail this requirement raise flag to estimate from future datasets. Recovery -------- * Estimate the charge injection level in each column of each CCD quadrant, across 6 independent images and therefore not subjected to cosmic rays, are within 1 ADU of one another. If above 1 ADU, measure variation for incorporating into the VIS_CTI PE and CTI calibration pipeline. * Perform stacking with cosmic ray masking procedure for each set of 6 images with identical charge injection settings to calculate master charge injection frame. * Check there are positive values in all pixels corresponding to expected charge injection locations, to determine IG1 / IG2 settings where charge injection fails. Quality control parameters -------------------------- DataModel: ``_ Contact person -------------- VIS instrument scientist .. raw:: latex \clearpage