.. index:: Gain (VIS), Photon Transfer Curve (VIS); Calibration observations .. _calobs-vis-ptc: **CALPRODUCT-VS-011:** VIS Photon Transfer Curve (PTC) ====================================================== .. include:: definitions.rst Parent requirement ------------------ | `R-CAL-B-VS-4360 `_ Scheduling ---------- Weekly Time-critical ------------- No Objective --------- Obtain the photon transfer curve (PTC / gain) for every detector quadrant. Fulfilled by ------------ :ref:`calobs-block-pv-vis-ptc-cti-eper` Processing input ---------------- :command:`Ground Processing Input Data`: :command:`Data Description`: Processing method ----------------- Create a combined master flat for each illumination level. Create the photon transfer curves, and extract the gain from the pseudo-linear relation between variance and mean of the image pairs. Processing output ----------------- Updated gains for each detector quadrant. Required accuracy, constraints ------------------------------ TBW Processing tools ---------------- TBW Validation ---------- The gains of the various quadrants in the VIS CCDs range between 3.30 and 3.70 e-/ADU. The gain is also slightly dependent on detector temperature. If the gain of a quadrant changes by more than TBD %, then either the gain maps must be updated, or suitable adjustments made to the hardware (if possible, in flight). Recovery -------- Update the gain maps, or take corrective measures. Quality control parameters -------------------------- DataModel: ``_ Contact person -------------- VIS instrument scientist .. raw:: latex \clearpage