Gain Notes for Revolution 2668

Another revolution largely without data, very noisy and the whole is
		declared a BTI due to the inaccuracy of the energy determination and the
		extremely low gain and subsequent loss of events in the low-level
		discriminator.  BTI = 8609.4 to 8612.0 IJD.

This is one of the later revolutions in the mission where the calibration
sources have become so weak that for the best energy determination an
IC Gain History table is needed. These gain history tables are found
automatically by OSA, or can be downloaded from the DTU FTP site.
 
All offline gain/energy corrections (including the IC tables) are based on the
two Fe calibration sources in JEM-X1, for both units, then corrected iteratively
using the instrument background lines (Xe, backed up by Cu and Mo).

Latest OSA software (version 10 and higher) automatically cuts out the first
Science windows of data from each revolution to ensure that people do not use data
from the instrument-settling period. This process can be overruled, but only by
experienced users.
	
JEM-X1 rating: very poor - hence BTI between 8609.4 to 8612.0 IJD. 

JEM-X2 rating:  very poor - hence BTI.

The JEM-X2 corrections are based on the JEM-X1 Fe calibration sources, since
all the Cd sources are now too weak to use.

CAO 02/08/2023