Gain Notes for Revolution 2678

During the TOO observation of a newly active blackhole, Swift J1727.8-1613,
shows the effect of strong greyfiltering on the calibration data. Xe line is largely
absent after 8637.75 IJD. Hence the BTI between 8637.75 and 8638.5.
This matches perfectly with the beginning of the BHC observation - during
the preceding galactic observation there are no such problems. 

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 outside of BTI (Xe line positions within  4--5% of ideal)
	Rating is unknown during BTI (TOO blackhole observation)since there is no 
	reliable Xe line present in the data. 
JEM-X2 rating:  Good outside of BTI (Xe line positions within  4--5% of ideal)
	Rating is unknown during BTI (TOO blackhole observation)since there is no 
	reliable Xe line present in the data. 

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 05/09/2023