Subject: JEM-X Monday Meeting 2008-01-16
Date: Wed, 23 Jan 2008 13:12:17 +0100 (MET)

Participants: SB, NL, JC, NJW.

JEM-X status (SB): The evolution of the hardware trigger rate has
levelled out indicating that the increase in solar activity has
begun (solar cycle #24).
We have noted with interest that the recently proposed data compression
for SPI data can save as much as 16 TM packets.
Else no comments on JEM-X status; there is some noise from background
particles.

Crab calibration (SB, NJW): Common INTEGRAL Crab calibration exercise.
Diego Gotz represents ISGRI and proposes to use data from revolution
300 (that's where the small scale dither was performed). We have about
13 ks near on-axis of data which is very appropriate. We will make
a spectrum and submit for fitting together with ISGRI (and SPI) data.

Flux determination in j_ima_iros (NL): There is a decrease of the flux
in the later Crab calibration periods: revols. 541 and 605. This
occurs also in j_src_spectra and is independent of a very careful
selection of the very best anodes.
The flux change as a function of time is not identical at low and high
energy, in fact they change in opposite directions.
The electronic efficiency correction is under investigation. It has
previously been derived from the CBJ spectrum extraction.
It is a mystery what is the cause of this change. It could have
something to do with the (rising) background intensity. The next
Crab calibration will perhaps give an indication.
Each SWID that goes into the analysis must be checked for deviations
from standard instrument settings.

/NJW