SXT Status Report
                        28 April -  11 May, 1998
                             (Weeks 18-19)
  
                        D. McKenzie, H. Hudson


SUMMARY

Activity was high, with 14 M flares and two X flares during the interval.
The instrument continues to operate well.

SOLAR ACTIVITY

Yohkoh got many flare triggers and some splendid observations.  The
many flares were accompaniend by correspondingly many CMEs, and we seem
to find that flares with clearly defined soft X-ray eruptive structures
are more common than they had been in the last cycle. See the science
nugget for May 8 for one nice example. There were many other items of
real scientific interest, including a remarkable set of transequatorial
interconnecting structures that participated in the ejective flare and
CME of May 3, as reported in the science nugget.

During week 19, we supported XBP studies led by Karen Harvey, with
participation from SOHO and (yes!) TRACE. These observations were poor,
by our standards, because activity was at such a high level that
scattered-light background made them less sensitive than usual. Bright
points were detected, but not so many - we plan to make bright points the
subject of next week's science nugget, so please stay tuned.

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

Data archiving is complete through Week 16 (April 19).

Terminator acquisition continues. A normal spacecraft re-pointing 
was scheduled May 11, about 18 arc sec to account for normal 
seasonal fluctuations.

SCIENCE

Observational work centered on the XBP campaign (JOP 082), and upon
observations for JOP 059 and test exposures for JOP 080, which are
concerned with signatures of coronal heating (JOP 059) and coronal
and transition region dynamics (JOP 080).  These JOPs are SOHO campaigns,
led respectively by Robert Walsh (St. Andrews) and Frederic Clette (Royal
Observatory of Belgium).  More information on JOPs, including a summary
of JOPs past and future, is available on the web at URL:
	http://sohowww.nascom.nasa.gov/~soc/JOPs/

The scheme of weekly reporting by the SXT Chief Observer on Web pages
has continued, but we missed one date because of the busy joint
observing schedule.  The current "science nugget" is now located under
the official Yohkoh Web site at ISAS, and its URL is

http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html.

The previous science nuggets reported by SXT chief observers are listed in

http://www.solar.isas.ac.jp/sxt_co/index.html.

The newer ones are:

980320.html  Cavity with bright core
980327.html  AR dependence of flare characteristics
980403.html  Message from the back side of the Sun
980410.html  Further analysis of the 7-Apr-97 flare CME
980417.html  Growth and Decay of AR 8203
980424.html  Proton flare, April 20, 1998
980508.html  M flare ejecta and loop filling

The last entry is identical with SXTweekly.html and contains links to
current-week operations information. We SXT chief observers seem to
like this system - it helps us make current affairs available - and
we would always appreciate feedback.  

OPERATIONS ISSUES

Week 18, five KSC passes lost to HALCA.
Week 19, six KSC passes lost to HALCA.

VISITORS AND PERSONNEL

No personnel changes. H. Hudson was away from ISAS both weeks, but
spent week 19 at the SOHO EOF enjoying an entirely different perspective.

SEMINARS

None.

TOHBANS

Tohbans for Week 18

     SSOC : S. Masuda, T. Tanaka
     KSC  : S. Ueno, K. Fujiki
     SXT_CO: D. McKenzie 
     SXT_SW: - 

Tohbans for Week 19

     SSOC : K. Marubashi, H. Watanabe
     KSC  : K. Fujiki, H. Tonooka
     SXT_CO: D. McKenzie 
     SXT_SW: -