Changes between Version 34 and Version 35 of Background_Dark_Model

Timestamp:

Apr 5, 2012, 4:31:27 PM (14 years ago)

Author:

watersc1

Comment:

--

Background_Dark_Model

@@ -9 +9 @@
  1. Construct three new darks: 2011-05-01 - 2011-08-01; 2011-08-01 - 2011-11-01; 2011-11-01 - 2012-04-01.  These will minimize the dateobs trend  observed over this range.
  1. Construct noisemaps for 2009-01-01 - 2010-09-01; 2010-09-01 - 2011-05-01 to match the variance shifts shown below.
+
+=== Fixed Gain test ===
+
+I reran the g-filter footprint, using all previous improvements with the addition of fixing the gain for every cell of the entire detector to a single value of 1.1.  The same processing and analysis was done, generating a higher number of false positives than the previous (noisemap) reduction:
+
+[[(Image(07_fixedgain.png,400px)]]
+
+||Reduction || All N=1 || All N=12 || Good flags N=1 || Good flags N=12 || QF Perfect N=1 || QF Perfect N=12 ||
+|| fixedgain ||  196192 || 419942 || 166336 || 415331 || 87839 || 402359 ||
+
+However, looking at a plot of the change in false positives for each detector cell as a function of the gain ratio (header quoted gain / chosen fixed gain of 1.1) shows that this increase is largely due to a number of detectors going from a gain less than 1.1 to this fixed gain.  If we preferentially select only those cells that have quoted gains larger than 1.1, we generally see a dramatic improvement in the false detection rate, at only a minor change in the number of 12-detection measurements (red points).
+
+[[(Image(fixedgain_improvement.png,400px)]]
+
+This suggests that making the change to use any quoted gain below a threshold, and clipping all others at that threshold may make an improvement in the false positive rate.
+
+||Reduction || All N=1 || All N=12 || Good flags N=1 || Good flags N=12 || QF Perfect N=1 || QF Perfect N=12 ||
+|| Simulated gain clipped || - || - || - || - || 73591 || 397913 ||
+
+Simulating this with the noisemap/fixedgain test data gives only a negligible change.  This is likely due to the fact that only 346/3840 cells have gains higher than 1.1.  These cells account for 14831/76966 single detection sources in the noisemap data, and 11456 sources in the fixed gain data.  Therefore, even though these cells do have an larger than average false detection rate, the total rate is not significantly improved by correcting the gains.
 
 == April 4, 2012 ==