Subject: JEM-X Monday Meeting 2005-09-05

Present: JC, SB, NL, CBJ, NJW

JEM-X status (SB): Hotspot active again. The average count rate through
          September 4 (24 hours) is 4.2 cts/s. Thew count rate is
          highly variable so at periods there might be data loss due
          to buffer flushing at end of ScW. The rate of 5-buffer losses
          has also increased.
          The hotspot counts extend up to PHA <~ 115 (E ~ 6 keV) where
          the rejection becomes effective.
          We can consider an onboard patch to exclude the hotspot region
          to save telemetry (a memory patch). This would save telemetry
          but deadtime would still be increased.
          Another way could be to change the risetime rejection because
          the "sparc" counts have very short risetimes (this will avoid
          the increase of deadtime since events are rejected before
          the position algorithm is started).
          Perhaps we could analyze diagnostic events from the hotspot
          or suggest a diagnostic data taking e.g. during the OMC
          flatfielding campaign.
          
Gain correction (NJW): New gain history tables to use with j_cor_gain
          and parameter 'COR_gainModel'=0 (linear interpolation).
          The 3-5 keV flux variation in revolution 39 is partly removed.
          There is still jump between IJD 1134.5 and 1135.0. The increased
          level in the beginning of the revolution can be due to higher
          gain with higher efficiency.
          There is also a strange jump in revolution 42.
          
Spectral variations (JC): When analyzing spectra from different time
          periods it is important to use a fixed source position
          (including a user catalog, parameter CAT_usrCat=... ).
          This must be emphasized in the Analysis User Manual.
          On the other hand the reported error on the position from
          j_ima_iros must be taken into account in the spectral extraction
          process when assigning errors.
          
Source positions from j_ima_iros (NL): A comparative study of position
          accuracy between CBJ software and j_ima_iros shows definitely
          worse precision for the latter. Is the iteration loop stopped
          to early?
          We will try to run the j_ima_iros images over a large energy
          band and apply the CBJ source position algorithm on those
          images in order to track down the reason for the semi-bad
          positions.

SDAST meeting (NL): SMN will not be able to come, we have 'a statement
          of intention' from Tim Oosterbroek. Else we expect Peter Kretschmar,
          Stefan Larsson, Stéphane Paltani, and Andrii Neronov.

NOB


/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