Subject: JEM-X Monday Meeting 2006-01-30

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

JEMX status: JMX2 was activated 2 revolutions before Earth observation
and has been on up to and including revol 402, although with no science
TM packets. Has been running in a stable way but with a hot stripe
(as a result of the backplane position being indetermined).
JMX1 has its usual small hot spots but not in an alarming way.
Gain: It takes about 2 hours from HV-on to gain stabilization (there are
indications that this is slower for JMX2 - we must have a look at that).

Earth observation.

For JMX2 there are gain effects in the lightcurve for the Earth observation
that either can be attributed to threshold changes or higher efficiency of
the rejection criteria for high gain.

The DXB spectrum extracted as the difference between the 'Right-on-Earth'
spectrum and the 'Completely away from the Earth' spectrum gives a good
match between JEMX and ISGRI. But it deviates from the HEAO-1 DXB
spectrum. SB has made an extraction by combining as much information
from the lightcurve by exploiting the fact that there is a smooth variation
of the lightcurve in each energyband.

The observation has been carried out pointing towards RA 252 and Dec -61,
which has a galactic latitude of about 10 deg i.e. not so far from the
galactic plane. [This position is a result of a later correction; at the
meeting the coordinates 180,-20 were (falsely) assumed].

The jump at PHA=115 in JMX1 is positioned at PHA=160 in JMX2 (for historical
reasons). This must be remembered when analyzing JMX2 data (count rates
in the same energy bands will differ between JMX1 and JMX2 for low energy).

The gain in JMX1 is higher than it has been for a very long time.
This is a good thing for seeing the low energy part of the DXB.

We might ask for HV-on at an earlier time for the next Earth observation
to reach gain stabilization before the real Earth observation starts.
Previously we have not seen too high background rates. One hour earlier
could be an advantage - the count rate increase should be checked in
IREM data. The other possibility is to start the Earth observation
somewhat later in the revolution. This will imply a smaller coverage
of the FOV by the Earth but on the other hand the observation will last
longer and hence give more data.

New GRB (SB): 3 deg offaxis, hence visible from JEM-X if not too weak.

Alignment and spectral extraction( NL): Not much progress during the
last week.

AOB: Upcoming Crab calibration, we must supply ISOC with detailed HV
steps.

/NJW

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Niels J. Westergaard
Danish National Space Center
Juliane Maries Vej 30, DK 2100 Copenhagen O
Phone: +45 35325705; FAX:  +45 35362475