Subject: JEMX Monday Meeting

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

JEM-X status: IREM crash (rev ~249) caused a broadcast of values 65535
      that makes the JEM-X DPE switch off the HV.
      About 20 of these crashes have occurred and since JEM-X has its own
      switch off mechanism by high count rates we will decouple from IREM.
      NL is preparing a change request.
      The situation is also more complicated because the switch-on procedure
      by MOC uses the database with old values for HV settings which means
      that JMX1 is started at too high voltage (right after switch on
      this means ~30% higher gain) which puts the anodes at risk.
      This matter will be discussed at the coordination meeting this week.
      
      There is no need to reactivate the dormant JEM-X unit from time to
      time. We have seen that the ageing is braked.
      
      The test for gas condition i.e. increasing VC (Cathode voltage)
      about 30% requires probably an hour or two under stable conditions
      (more than 5 hours after out-of-radiation-belt and well before
      re-entry). An OMC flatfielding period could be used.
      
Next Crab calibration:
      JMX2 should be reactivated at least one revolution before the
      calibration to achieve temperature and gain stabilization.
      
      We propose smaller dither steps for better mapping of collimator slant.
      
Dither pattern change: We have no strong opinion on how the center point
      changes from cycle to cycle but we want as narrow a dither as possible.
      
On-board software change: ILR has made the patch and it should be tested
      on the FM1 lab model.
      
Stripes in shadowgrams and images: NL: The pixelfold change of the shadowgram
      does not increase the detected source strength - it is actually
      decreased by about 5%. CBJ: The collimator visiblity with a strong
      on-axis source is about 5% better when pixelfold is included.
      
Background and Neutron monitor data: SB has shown a close correlation
      between the JEM-X background (when the rate of accepted counts is
      below 50/s i.e. excluding solar events) and the Oulu Neutron Monitor
      data. The background has increased by 50% relative to the start of
      INTEGRAL mission but when comparing to the previous 3 solar cycles
      there is hope that the increase will stop soon.

AO3: We are involved in about 10 proposals.
  
/NJW
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Niels J. Westergaard
Danish Space Research Institute
Juliane Maries Vej 30, DK 2100 Copenhagen O
Phone: +45 35 32 57 05; FAX:  +45 35 36 24 75