Gain Notes for Revolution 1707

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.: The second half of this revolution contains an observation of SCO X-1
during which strong, non-linear changes in the instrument gain occurs, as well
as grey filtering. The grey filtering removes most of the calibration photons
as well as the instrument background used to verify the energy corrections.
This means that at some points in the revolution (i.e. during on-axis observation
of SCO X-1) it is not possible to correct the data for the non-linear variations,
nor quantify how well the corrections have been performed. Usually, it is assumed
that if Science windows both sides of a weak, misfitted SCW are correct, so is the
SCW for which it was impossible to make an individual determination.
 

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 very good gain
correction with all science windows (taken 2 at a time) having a Xe level 
within 2-3% of the ideal, except for the settling points and a handful
of weak, misfitted SCWs - see caveat at top of page. 
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: 

The Xe line analysis performed using the IC table shows excellent gain
correction with all science windows (taken 2 at a time) having a Xe level 
within 1-2% of the ideal, except for a couple of settling points at the
beginning of the revolution. For this unit even the SCO X-1 observation
has been verified to within 1-2% of ideal suggesting that JEM-X1 is
similarly correctly calibrated, even though some SCWs can't be verified.
This is because the two units have different grey filter settings that
sometimes benefit JEM-X2. 

As usual, it is recommended that users avoid the first few science 
windows for energy-sensitive applications (automatically removed by OSA 10.0).

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 02/08/2016