Gain Notes for Revolution 1848

This is one of the later revolutions in the mission where the calibration
sources have become so weak that for the best energy determination and
IC Gain History table is needed.

N.B.: This revolution contains two additional commanded switch-off/switch-on
due to Loss of Signal from the Kiruna ground station. During the settling periods
after every switch on (3 periods in this case), though average gain determination
may appear good, variations in gain and temperature dependence across the detector
plates mean that the general quality of the energy determination is degraded 
regarding individual photons. For both units the fainter instrumental lines from
Cu and Mo are washed out by these effects, indicating poorer energy resolution
even though the Xe line centre, integrated for each science window, can be placed 
within 2% of the ideal.
 

To get optimal results with this revolution it is necessary to use the IC gain history.
See notes in revolutions prior to revolution 1433 to find out how to do this
if you don't already know.

All offline gain/energy corrections (including the IC tables) are based on the
two Fe calibration sources in JEM-X1, for both units.

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: Excellent to Very Good (Xe line position within about 2% of ideal)
but energy resolution compromised by multiple breaks in data-taking.

JEM-X2 rating: Very good (within 2-3% of ideal) but same caveat about reduced
resolution applies.

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

CAO 11/08/2017