Changeset 39879

Timestamp:

Dec 16, 2016, 4:11:17 PM (10 years ago)

Author:

watersc1

Message:

Update of KH effect discussion with dates and voltages.

File:

• trunk/doc/release.2015/ps1.calibration/calibration.tex (modified) (1 diff)

trunk/doc/release.2015/ps1.calibration/calibration.tex

@@ -1009 +1009 @@
 \subsubsection{Koppenh\"offer Effect}
 
-The Koppenh\"offer Effect was first identified (DATE) by Johannes
-Koppenh\"offer (MPE) as part of the effort to search for planet
-transists in the Stellar Transit Survey data.  He noticed that the
-astromety of bright stars and faint stars disagreed on overlapping
+The Koppenh\"offer Effect was first identified in February 2011 by
+Johannes Koppenh\"offer (MPE) as part of the effort to search for
+planet transists in the Stellar Transit Survey data.  He noticed that
+the astromety of bright stars and faint stars disagreed on overlapping
 chips at the boundary between the STS fields.  After some exploration,
 it was determined that the X coordinate of the brightest stars was
 offset from the expected location based on the faint stars for a
-subset of the GPC1 chips.  The essence of the effect was that the
-bright stars were advanced along the serial register more quickly than
-they should have been.  The brighter the star, the more the charge
-cloud was pushed ahead on the serial register.  The amplitude of the
-effect was at most \note{XXX}.  Only the \note{2-phase} chips suffered
-from this effect.  By adjusting the \note{which?} voltages on the
-camera, the effect was prevented in exposures after \note{DATE}.
-However, this left \note{XXX,XXX exposures (XX\%)} already
-contaminated by the effect.  
+subset of the GPC1 chips.  The essence of the effect was that a large
+charge packet could be drawn prematurely over an intervening negative
+serial phase into the summing well, and this leakage was
+proportionately worse for brighter stars.  The brighter the star, the
+more the charge packet was pushed ahead on the serial register.  The
+amplitude of the effect was at most $0\farcs{}25$, corresponding to a
+shift of about one pixel.  This effect was only observed in 2-phase
+OTA devices, with 22 / 30 of these suffering from this effect.  By
+adjusting the summing well high voltage down from a default +7 V to
++5.5V on the 2-phase devices, the effect was prevented in exposures
+after 2011-05-03.  However, this left 101,550 exposures (27\%) already
+contaminated by the effect.
+% This uses PV3 3-pi exposures:
+% group           N(<2011-05-03)    N(total)  %
+% PV3-3pi         101550            375573    24.47
+% exptype=OBJECT  229272            936879    27.04
+% ALL             322922            1163377   27.76
 
 % \note{was there is significant difference using a surface brightness version?}