Gain Notes for Revolution 2051

This revolution was the first in a series of SPI annealing revolutions which strongly
affected both JEM-X revolutions so that gain was strongly depressed and all instrumental
lines, including Xe were extremely weak, limiting the accuracy of the instrument
gain determination. Where realistic fits to the calibration data could be made,
it was possible to calibrate this revolution as well as for non-annealing revolutions,
but for many of the Science Windows, no Xe line as visible to verify the calibration.
However, assuming that gain changes very slowly, and that SCWs either side of a
very weak SCW are well-calibrated, the bookended SCWs should be equally well calibrated.
This is a rare revolution where even the Xe line can barely be seen integrated over
all SCWs.

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.
 

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: Overall:Very Good. Where a fit can be made with a realistic half-width, 
Xe line is within 2-3% of ideal, but very many SCWs can't be fitted at all. 
No meaningful improvements can be made. Extreme weakness of Xe line indicates 
a simple lack of counts to give the necessary statistics. 

JEM-X2: Overall, excellent, but all the same comments apply as for unit 1.

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 04/02/2018