Subject: JEM-X1 status

Dear SDASTers,

we've just had a little meeting to discuss the JEM-X1 performance, now that it's
had a little pre-calibration try out. The results look promising. Here's a
summary of the main points:

1) Main conclusion is that the unit's working well, and will be our workhorse
	for the next 6 months or so
2) There has been no significant increase in the number of dead anodes
3) The old hotspot is gone, though another smaller one has been seen, but this
	is very close to the edge and would easily be  removed by using the
	radiusLimit parameter. JMX1-DETE-MOD must be updated accordingly.
	Both hot spots appear to be linked with dead anodes.
4) No great changes in gain, though there is still a modest amount of decay
	gain after switch on. Since this is so small, and certainly does not
	lead to dangerously high starting gain levels, NL suggests getting
	rid of the two-step HV switch on after each perigee.
5) Currently gain is quite low, and HV should be set up 1 step (a compromise
	between NL's optimism and CBJ's caution). Upper level cutoff however,
	will be kept as it is since it doesn't threaten the Xe line at the
	slightly higher gain, and we don't want to increase background
	telemetry. There is a posssibility that that gain will increase 
	somewhat and then stabilise after 20-30 revolutions just as it did
	at the beginning of the mission.
6) Xe line looks good and is about where is should be. So no strange gain
	evolution during the long switch off period.
7) The latest patch is working properly
8) The coming Crab calibration will be very important for the instrument, and
	SB's all for getting the unit calibrated at the relatively low gain, 
	and so the next calibration could be done with higher gain, so that
	we have a good understanding of the whole range of performance, rather
	than trying to hit a middle gain value both times.
9) The rim background appears to have decreased significantly, but this may
	only be due to optimimal solar/CR conditions during the measurements.
	At any rate, things don't look worse than before.
10) The JEM-X2 patch will be cancelled and that unit kept in its current
	configuration since we now know so much about its behaviour and
	response, and have lots of data in this configuration which could do
	to have a fine-tuned response.
11) We've had some ECAL alerts for JEM-X1, (FAST4, FAST3, SLOW4) but clearly
	these are not important changes in the amplifier behaviour, and
	JMX1-ECAL-MOD needs updating.
	
All of the above is good news for both the IT and for the JEM-X users. Let's
hope this bodes well for the coming months.

Best wishes,

Carol Anne

.DANISH.SPACE.RESEARCH.INSTITUTE.DANISH.SPACE.RESEARCH.INSTITUTE.DANISH.
Dr. Carol Anne Oxborrow
Email: oxborrow@dsri.dk	Homepage: http://www.dsri.dk/~oxborrow
Telephone (direct): +45 35 32 57 33
Telephone (secretary): +45 35 32 57 01
Fax: +45 35 36 24 75