Gain Notes for Revolution 1557

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.

NB: The first half of this revolution is strongly affected by the flaring of
blackhole V404 Cygni which causes periods of strong greyfiltering during which it is
not possible to see either the Fe lines that are used for gain calibration or the
Xe line used to verify the energy determination. Energy correction cannot be relied
upon to be correction during the first part of the revolution. 
 

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: 

The Xe line analysis performed using the IC table shows poor gain
correction during the first part of the revolution, 
with most science windows having a Xe level within about 5% of the ideal, though
there are many outliers due to poor or non-existent fitting of both the Fe
calibration spectra and the Xe lines used to confirm the energy corrections. 
In the second half of the revolution, where the flaring has stopped, the gain
correction performed with the IC tables shows very good energy determination
with all the SCWs having a Xe line position within 2% of the ideal.
As usual, it is recommended that users avoid the first few science 
windows for energy-sensitive applications (automatically removed by OSA 10.0).



JEM-X2: 

Identical comments as for JEM-X1.

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 13/7/2015