up

sections/biasStability.rst

@@ -1,21 +1,19 @@
 Bias stability
 ############################################
-Bias instabilities are of 2 kinds :
+Bias instabilities (typically above the 1-ADU level) are observed over a significant number of sensors for both ITL and e2v CCDs. The main issues are referred as :
 
-#. ITL bias jumps
-#. e2v 2D shapes.
+#. The ITL bias jumps : large variation of the column-wise structure from exposure to exposure.
+#. The e2v yellow corners : residual 2D shape of the bias even after 2D-overscan correction. These residuals depend on the acquisition sequence and of the exposure time.
 
-Both observed in Run 6 and deeply studied. Issue 1 considered as hardware-level issue, tried to mitigate issue 2 by acquisition optimization in Run 7.
+Both issues were observed and deeply studied in Run 6 EO data and deeply studied. The ITL issue is thought to be an hardware-level issue (phase shifts between Readout Electronics Boards). We tried to mitigate the e2v issue by optimizing the acquisition configuration in Run 7.
 
-For the baseline configuration (see conclusion), three stability runs were recorded :
+For the baseline acquisition configuration (see conclusion), three relevant stability runs were recorded :
 
-#. Run E2136 : 15-s darks with long delays
-#. Run E2236 : 50 15-s darks, 50 biases
-#. Run E2330 : 15-s and 30-s darks with delays
+#. Run E2136 : 15-s darks with some very long delays throughout the run
+#. Run E2236 : 50 15-s darks, 50 biases recorded with 30-s delays between exposures
+#. Run E2330 : 15-s and 30-s darks with variables delays between exposures
 
-eo_pipe bias stability task : bias +  serial overscan correction, mean of the image
-
-Plots 
+To process these runs, the eo_pipe bias stability task is used : for the ISR part, a serial ('mean_per_row') overscan correction and a bias subtraction (computed from the corresponding B-protocol run) are applied. The final data product is the mean of the per-amplifier science image over the full set of exposures of the run. Two typical examples are shown in the figures below.
 
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