Gain Notes for Revolution 276
	
JEM-X1: 

All of the JEM-X1 data from this revolution has now be declared part of a
Bad Time Interval due to the gain suppression and other effects that demonstrate
that the quality of the data has been compromised by the high radiation background.
The BTI is: IJD = 1842.0 to  1843.0, and the ISDC analysis software will
disregard science data from this time period.

The little data that exists for this revolution was taken at a time
when background radiation due to solar activity was very high, immediately
prior to switching off the instruments. Though the gain smoothing fits the
observed gain on the calibration spectra well, the gain corrections for this
data are still incorrect. This is because the high radiation levels charge the
plate more than usual and therefore depress the gain of the instrument. This
gain decrease is not picked up at the calibration spectral areas because they
always carry a heavy charge load due to the irradiation of the calibration
sources themselves. Consequently the gain corrections that are applied to
the science events from all over the plate produce energies that are too low.
This can be seen clearly in the fitted xenon, molybdenum and copper lines 
(follow the links labelled `Uncorrected').

This problem is now corrected by using a gain history table that is corrected
offline and delivered to ISDC as an instrument characteristics (IC) table.
The OSA 6.0 scripts, and later, can automatically find these IC tables, if they
exist for a particular revolution, and use them instead of the default tables
generated automatically at ISDC. The Xe/Cu line data shown here, is produced
using corrected events processed with j_cor_gain 7.2 and the IC gain history
table. The IC gain history table is also appended to this table in the last
column, if you wish to download it and use it separately, as described below.



A QUICK FIX for archived data processed with j_cor_gain 6.4 or earlier, is to 
multiply all the derived energy values by a factor of 29.6/28.2. However, a
better solution is to download the latest IC files for JEM-X1 and reprocess
the raw data from the COR level onwards using j_cor_gain 7.2 or later (OSA 6.0).
OR you can download the corrected gain history table found in the last column
of the table containing these notes. Put this corrected table (all Cd and Fe
peak positions multiplied by 28.2/29.6) into your own private subdirectory,
<myIMODdir>, unzip it (gzip -d <filename>) and in the OSA GUI set the hidden 
parameter gainHist:
gainHist="<myIMODdir>/<filename ending in .fits>[JMX1-GAIN-OCL,1]"
This method can be used with j_cor_gain 6.4 and all later versions.


The unit was not activated at all during revolution 277 because of continuing
high solar activity.


JEM-X2: there is no gain history data or science data for this unit during
revolution 276.


CAO 10/11/2006