Gain Notes for Revolution 2685

This revolution contains a TOO observation of the strong
	black hole source Swift J1727.8-1613, which despite the
	additional TM packets given to JEM-X1, still swamps
	the Xe line and makes it hard to determine the goodness
	of the gain/energy determination.
Also, the gain of the instrument is well below 20 chans/keV
	for most of the revolution, which therefore must be
	declared a BTI throughout. BTI = 8654.6 to 8657.2 IJD .
	This is due to high particle flux (solar activity) during
	the revolution. 

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: Good enough (within about 5% of ideal for
		periods with a visible Xe line, and except for the settling zone. 
		Misfits to non-existant Xe lines are shown by their unphysical widths.)

JEM-X2: No science data for this revolution.

CAO 21/09/2023