Subject: JEM-X Monday Meeting 2006-12-11
Date: Fri, 22 Dec 2006 11:07:26 +0100 (MET)

Participants: SB, JC, NL, CAO, CBJ, NJW.

JEM-X status (SB): Datataking stopped 2006-12-06 due to high solar activity
with high background. Extrapolation of the IREM curve indicates an almost
back-to-normal level by 2006-12-12.

SB has made a list of all resets due to high count rates.
 
At high count rates the slow anode signal may exhibit pile-up leading to a
distortion of the energy spectrum. Sco X-1 is the only (persistent) source
that can provoke this situation. SGRs may also do it. The best way to describe
the effect is an extra noise component leading to a very moderately degraded
energy resolution.

OSA6 deliveries (NJW, JC, CAO): j_ima_iros-1.7.1 with corrected image and flux
units has been delivered. j_ima_src_locator has been delivered as an official
ISDC tool but not for OSA6. j_ima_mosaic has now dynamic memory allocation for
the input images. j_cor_gain has also been delivered - small bugs only.

No news on an update of mosaic_spec.

j_ima_iros development (NL): The cause of the discrepance between
backprojection and forward raytracing has been identified as an error
in the peakfinding and locating function.
The correction of this error has led to improved source fitting.
The ISDC misalignment matrix should be introduced. One should be careful,
however, because the j_src_spectra and j_src_lc use the old version.

Radiation belt passages in the future (SB): Proton belt is (almost) symmetric
around the magnetic equator, which is tilted by 11 deg relative to the
usual equator plane. INTEGRAL is almost in a polar orbit. The perigee is
over Antarctis and the altitude at the equator plane is a good deal higher.
It seems possible to change the orbit without getting too deeply into the
radiation belts.

Gain suppression (CAO): The position of the Xe line monitored in a number
of revolutions where the instrument has been switched off due to high
count rates. Just before the switch off one could expect problems with
the Xe line measured energy. Rev. 252 does not show this, however.
But for revol. 218 there are some change in the derived Xe-line energy.
A closer look at the data used for fitting can be useful.

/NJW