Gain Notes for Revolution 1656

This revolution is heavily affected by the observation of SCO X-1 which causes a huge
drop in gain of the microstrip plates and also has autonomous grey-filtering which
strips out both Xe line photons in the science data and calibration spectra photons.
This means that the energy calibration is doubly afffected - firstly by a lack of
calibration data with which to the initial corrections on the data, and secondly,
by the lack of background lines with which to confirm the quality of the energy
corrections. In this situation where many Science Windows lack a fittable Xe line,
we assume that so long as the visible Xe lines fall within the useable range then
the SCWs we cannot verify are probably of similar quality. All the data from
this revolution will be marked by considerable noise in the energy determination -
up to 5-6 percent either side of the ideal correction.


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: 

The Xe line analysis performed using the IC table shows good gain
correction with all visible science windows (taken 1 SCW at a time) having a Xe level 
within about 2% of the ideal, except for the usual settling points. However there
are many points that cannot even be seen on the figure, due to misfitting of very
weak Xe lines due to grey filtering and other problems when viewing SCO X-1. It can
only be presumed that their energy determination is of a similar quality. 
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, though somewhat fewer 'invisible' Xe line
points.

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 5/04/2016