SXT Status Report
                     1 June, 1998 - 14 June, 1998
                             (Weeks 23-24)
  
                        H. Hudson,  D. McKenzie


SUMMARY

Activity was moderate, and SXT has operated well. We've been busy
with joint observations scheduled for TRACE, SOHO, and ground-based
observatories.

SOLAR ACTIVITY and SCIENCE

The GOES level (see the plots, for example, on our weekly SXT Web
pages) remained at mid-B level, trending upwards towards the end
of the interval. By 12 June, nine C or greater including one
beautiful over-the-limb M event - an example of a spiky post-flare
loop system, of the sort seen occasionally with a side-on view.
The largest sunspot group was AR 8232, about which more later,
with a peak sunspot area of 360 millionths.

During week 23, SXT took part in SOHO and TRACE observations of
AR 8227, with Karin Muglach of ESA leading the SOHO effort. 
This was the region TRACE dedicated a two-week session
towards, and the resulting data set (not yet described by a 
science nugget, because too many things are happening to keep up)
could best be described as "unprecedented". We immediately started
thinking about making this data set the focus of the CDAW this
fall.

During week 24, a Hida Observatory campaign (Kurokawa), focusing
on flux emergence and jets (Shimojo). This campaign has been less
successful, partly because the cloud cover at Hida is (honestly)
worse than at TRACE or SOHO. Nevertheless we have one excellent
set of PFI-dominant data, filled with interesting phenomena, so
it may be that the campaign has been a success in spite of the
monsoon.

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

Data archiving is complete through Week 22 (May 30).

Terminator acquisition continues. We scheduled two spacecraft
re-pointings to help keep the database dense in space and full
in time. The X and Y rms values for sun center location are
only a few pixels, and we believe (based on watching how well
the Al.1 movie images look) that we are really doing the right
thing here. Images from June 12, for example, showed virtually
no trace of stray light.

SCIENCE

The two current "science nuggets" are (5-Jun) a summary of Nakakubo-san's
Master's thesis, which contains results from her automated XBP search
program; and (12-Jun) a splendid example of the sigmoid/halo CME pattern:

 5-Jun-98: X-ray Bright Point Number Variations  
12-Jun-98: Sigmoid => Halo CME => Storm?!  
 
To access these, go to 

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

As usual, the current week is also on

http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html. This shows the weekly
SXT operations report as well as a GOES plot indicating the Yohkoh data 
currently available on line.


OPERATIONS ISSUES

Week 23: 1 pass was lost due to conflict with AKEBONO,
         4 passes were lost due to conflicts with Planet-B.
Week 24: 5 passes were lost due to conflicts with Planet-B.

Next week we begin to lose still more KSC telemetry  passes to PLANET-B
(on to Mars!).  Launch countdown begins at 15:00 JST on July 3, culminating
in launch at 03:30 JST.  Yohkoh may get no KSC passes these two days.
In the meanwhile, our operations will be hampered by lack of upload
flexibility.  After launch, KSC will act as a backup antenna station
for the critical operations phase, so Yohkoh may have to give up a few
passes each week until November.

VISITORS AND PERSONNEL

No personnel changes.

SEMINARS

June 4:

H. Hudson (SPRC/ISAS): "The HESSI mission" - or - "A photospheric flare wave"
S. Watari (CRL): "The distinction between metric and interplanetary Type II's"

Both of these talks were inspired by interesting things heard at the
AGU/SPD meeting in Boston.

TOHBANS

Tohbans for Week 23

SSOC : S.Watari                
KSC  : M.Kasahara, T.Tanaka
SXT_CO: D. McKenzie, H. Hudson 
SXT_SW: -

Tohbans for Week 24 

SSOC : J. I. Khan,?. Ashizawa
KSC  : T. Tanaka, J. Sato
SXT_CO: H. Hudson, D. McKenzie 
SXT_SW: -