Gain Notes for Revolution 2663

N.B.: This revolution contains a sudden 20-30% drop in gain for no
		apparent reason. This glitch has been removed from the energy
		corrections to within 5\%\ of ideal, so need not affect individual photon
		energy values. However, the dip in  gain is sufficiently extreme that events may
		have been lost in the low level discriminator, thereby  weakening the low
		energy part of the spectrum. Therefore a BTI is declared, for poor instrument
		parameters, between 8597.0 and 8597.4 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: Outside of BTI, results are excellent (within about 2\%\ 
		of ideal, except for settling zone). During BTI gain accuracy is within about 5\%\ of
		ideal, but precise effect of the low-level discriminator makes spectra below 10 keV
		distinctly weak compared to the rest of the energy range.

JEM-X2 rating:   Excellent outside of BTI (within 2\%\ of ideal,
		except for settling zone). During BTI scatter in Xe line position is \pm7\%\ and effect
		of low-level discriminator will be to remove permanently events in the low end of
		the spectrum. BTI= 8597.0 IJD to  8597.4 IJD

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 01/08/2023