SXT REPORT FOR WEEKS 41-42 ; 4 Oct 1993 - 17 Oct 1993               

GENERAL STATUS

     
     The SXT and the spacecraft are working well.


PERSONNEL

     No significant personnel changes during the previous two weeks.
ISAS was a fairly quiet place last week as it was the time of the
autumn Japan Astronomical Meeting, which was held this year in 
Kagoshima.  Hugh Hudson left at the end of the week for a one week
trip to Tucson, AZ.


SOLAR ACTIVITY

     The solar activity increased somewhat during Week 41 with the
appearance of AR 7590 which produced one M flare on 9-Oct-93.  After
this flare, this region began to slowly decay.  Since that time
SXT has mostly been observing AR 7592.  The activity is now fairly
low, having reached B1 Goes level.

     NSO/Kitt Peak attempted to perform joint observations with
Yohkoh during this time.  Good observations were made from the ground
on 5, 8 and 9 Oct, coordinated by Karen Harvey.  Because of the level 
of activity, SXT had to be operated with ARS-1, which alternated between 
the two bright regions on the disk at the time.


SCIENCE PROGRESS

     Hudson and Lemen made a video movie of a flare observed on 11 July 
1992.  This is a good example of flare which shows loop filling by 
chromospheric evaporation.  Interestingly, it does not exhibit the "flare 
blob" structure that is observed in many SXT flare images.  We are now 
attempting to measure the physical parameters for the flare.

     A joint observing campaign began on 15 October with Pic du Midi.  
Brigitte Schmieder is coordinating the ground observations and the main 
objective of the observing campaign is to observe surges. 


SXT OPERATIONS

     The SXT operations have gone smoothly for the past two weeks.  As I
was one of the SXT Duty Scientists last week, I reviewed the acquisition
of terminator images.  These are images that are acquired as the spacecraft
is looking through the Earth's atmosphere at the Sun just prior to Sunset.
In these images, the X-ray flux is attenuated and only the visible light
is observed by SXT.  Such images are used to subtract the stray light
which is now present because of the failure of an entrance filter segment
last November.  It was discovered that the procedure was not being followed
correctly by the Duty Scientists for several weeks, and so we were not
getting good terminator images.  The op_first_guess software has now been
enhanced to make this job more automatic and hopefully, more fool proof.



                                                  James R. Lemen
                                                  19 Oct 1993