Gain Notes for Revolution 422
	
JEM-X1: This is a Crab calibration revolution, during which tests were performed
on the effect of changing the high voltage supply to the micro strip plate.
The effect is clearly seen: sudden drops in the gain before returning to the
nominal optimum voltage. This region of changed HV values is now officially
designated a BTI, meaning it will not be used for scientific analysis. The
official BTI periods of low HV are: IJD = 2280.57 to 2280.61 and
IJD= 2280.84 and 2280.96.


Version 6.4 of j_cor_gain, which appeared in OSA5.2
could handle all but the last change in HV. See the figures labelled `6.4'
to see this effect. 
Version 7.3 of j_cor_gain  which appears in OSA 6.0 is tested up to 8 different
time zones, and fits all zones of operation equally well. Of course
if the units are switched on and off more than 8 times we would run into 
problems, but with that many interruptions of the stable running of the 
instruments, the chances are that the science data would be of pretty poor
quality anyway.

This problem is now fixed in another way by using OSA 6.0 and later versions. 
The corrected gain history table, complete with average smoothed gain of the
detctor determined offline, is delivered to ISDC as an instrument 
characteristics (IC) file. The analysis scripts can find these
IC files if one exists for a particular revolution, and use it instead of the
automatically generated file. If you don't have OSA 6.0 installed, or do not
have the latest IC files use the following quick fix. The results shown here
without the label `uncorrected' have been derived using the IC gain history.

QUICK FIX: Download the corrected gain history table that has all the source
four outliers removed. This is to be found in column `Other data and results' of
the table containing these notes. Put the file in your own private directory 
say <myDir>, and unzip it (gzip -d JMX1_gainHistoryIC_rev0422_001.fits.gz).
When you run the OSA GUI you must correct the hidden parameter gainHist so that
it points to the the corrected gain history table:

gainHist = <path to myDir/<myDir>/JMX1_gainHistoryIC_rev0422_001.fits[JMX1-GAIN-OCL,1]



JEM-X2: Identical comments apply as for the JEM-X1 unit. The file to download
to do a quickfix using OSA6.0 (in the absence of the most recent IC files) is
JMX2_gainHistoryIC_rev0422_002.fits, and the value of the input parameter to
the OSA GUI is
gainHist = <path to myDir/<myDir>/JMX2_gainHistoryIC_rev0422_002.fits[JMX2-GAIN-OCL,1]

Also shown for JEM-X2 is the evolution of the Xe line position for both
OSA 5.1 and OSA 6.0 processing (j_cor_gain 6.4 and 7.3 respectively). Clearly
for the older software (labelled `6.4') there is a discontinuity in the
Xe line position caused by the incorrect discontinuity produced by the gain
smoothing. 

As with JEM-X1, the period of lowered high voltage (HV) supply is delared a BTI
which means that the ISDC will automatically cut this period of uncertain
detector response out of your data. The official BTI periods of low HV are:
 IJD = 2280.57 to 2280.61 and IJD= 2280.84 and 2280.96.

CAO 10/11/2006

All new Xe analysis for JEM-X2 was added after creation of new IMOD epochs
for the unit (12 and 13), containing new reference channels. The IC gain table
was accordingly updated and the results are shown here as `New' compared to the
results provided under `Old' which show the Xe position and evolution with the
previous set of reference channels. The IC table provided here is the updated
one with filename JMX2_gainHistoryIC_rev0422_002.fits. It is also available
in the ISDC IC package from which the correct version is extracted automatically
by OSA.

CAO 19/10/2007