Gain Notes for Revolution 774
	
JEM-X1: A quite normal revolution with fine gain fitting. All the data from 
this revolution should be useable. The Xe analysis confirms that the energy
determination for this revolution is okay, within about 4% of the ideal. 
However, as for all revolutions, the first few science windows should be
avoided in any analysis requiring very good gain determination. Since the
temperature variation of the gain has tripled since the beginning of the
mission, future version of OSA (version 8.0), including temperature dependency,
may benefit this revolution when it becomes available in 2009.


CAO 24/2/2009


JEM-X2: This was a calibration calibration for observing the Crab Nebula, and
it was the first time JEM-X2 had been switched on in 6 months. Consequently,
there is a long settling period for the first third of the revolution during
which the Xe line position varies wildly. It is advised that data from the first
3rd of the revolution are not used for scientific purposes. However the JEM-X
Crab calibration observations were scheduled right at the beginning of the
revolution and so this data has to be used, though it will evidently be of
very low quality. Usually however, this data would be ignored. The Xe line
analysis clearly shows the long settling period. It also shows that during
the last 2 thirds of the revolution the energy calibration is fine, within about
2% of the ideal. This data should be fine to use for scientific purposes.
Since there was a large temperature change in the instruments during this
revolution, using OSA8.0 may improve the stability of the gain calibration since
it can handle large temperature changes, and it is recommended that this
data be processed with OSA8.0 or later.

The early part of this revolution has been declared a BTI to eliminate the
period of rapid gain settling. The BTI period is IJD = 3331.4 to 3332.0

CAO 17/3/2009