SXT Status Report 
                     27 November - 14 December 1994
                                 ---
                            Loren W. Acton

SOLAR ACTIVITY

  Study of the x-ray sun at this phase of the solar cycle is providing
unanticipated delights and surprises.  Although M-flares are rare (but
we just had an impulsive one today!) the frequent outbursts of C and B
level flares that do not trigger the flare mode permit a new kind of
flare observing by SXT.  The continuation of normal-cadence quiet mode
observations provides excellent spatial coverage for remote influences
through the full frame images while maintaining proper exposure and
adequate frame frequency with the full-resolution partial frame images. 
This "new" mode of observing is especially good for eruptive events
associated with coronal mass ejections. 

OPERATIONS

  In addition to normal observing under ARS1 we have attempted some
filament observations by including one fixed target entry in the QT/Hi
partial frame image table.  A new program called GBO_OBS_COORD was
written to facilitate obtaining SXT pointing coordinates from
ground-based images of any type.  One quite nice one-day run on a
filament channel was obtained so far.
  Special observations are being carried out to characterize the small
but real orbital variation of CCD dark signal.  It has been shown that
this signal is due to actual dark current rather than read noise and
that it is primarily, perhaps totally, caused by the UV flood.  My
theory is that the very strong overexposure fills all the charge traps
in the CCD and we are observing the time constant of charge release from
these traps.  This work is nearing completion and the results will be
incorporated in an improved dark signal correction for SXT images.
  A very considerable effort has gone into straylight correction
software by Sam Freeland and in preparation and selection of straylight
correction images.  We anticipate a very considerable improvement in our
ability to correct for this pointing-dependent problem when this work is
finished.

  Progress was made by Hara san and Freeland on understanding the
3-Nov-94 data range error.  The Chief Observer (me) managed to
inadvertently reproduce the error by shortening the SXT morning UV flood
interval to its minimum value as part of the orbital dark current
experiment!

PERSONNEL

Tohbans for Week 49
   SSOC: Dhani  and  H. Tonooka
   KSC:  T. Takano and M. Takahashi
Tohbans for Week 50
   SSOC : T.Shinkawa and K.Marubashi
   KSC: M.Takahashi and S.Masuda(from 16.Dec)
SXT Chief Observer:
   L. Acton
SXT Systems and Data Engineer:
   S. Freeland

SCIENCE

Yohkoh science seminars were held at ISAS on 8 December.
   L. Acton	Coronal Heating
   K. Shibata	Discovery of Plasma Ejections in compact Solar Flares