SXT Status Report
                    April 18, 2000, to May 1, 2000 
                            (Weeks 17-18)

                         B. Handy, H. Hudson


SUMMARY

Activity was undisputedly low; we've been helping with SOHO JOP083 and
JOP119; SXT has had no technical problems.

SOLAR ACTIVITY

There were _NO_ M flares in this interval. As in the last reporting
period, there have many active regions, including one (8970) which
exceeded 1,000 millionths in sunspot area. But, no major flares.
The southern large spot group, 8970, matched the longitude of another
large spot group in the north, 8971. Their mutual CMP was about April 27.
Probably the proximity of these two has led to the TIL fireworks we've 
been enjoying in week 18.

OBSERVING CAMPAIGNS

Yohkoh supported SOHO JOP083 and an attempt at a new JOP119 oriented
towards transequatorial loops. During this period TRACE has been doing
a dedicated study of the quiet Sun (well, the timing was right, at
least).

Please see our webpages for more details about campaigns past and future:
http://isass1.solar.isas.ac.jp/sxt_co/sxt_catalog.html
http://isass1.solar.isas.ac.jp/sxt_co/sxt_future.html

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

Handy tackled the question of orbital decay with interesting results,
part of which are to be found in the science nugget for April 28,
"Running in Circles." Hudson continued to work with pointing jitter
during flare mode, but with no distinct conclusions yet. We carried
out test exposures for SFD-type images in the Mg filter, which look
passable (see http://isass1.solar.isas.ac.jp/~hudson/scratch/mg_sfd.html)
but grainy, probably owing to the high stray-light level in the raw
images.

SXT OBSERVING SEQUENCE TABLES

-------------------------------------------------------------
UT Date & Time                    Pass    Table ID
=============================================================
Tuesday AM     17-APR-00 18:16     4      000417 P4 ARS1 DKCAL
Tuesday PM     17-APR-00 11:16     1      000418 P1 ARS2 JOP83+DF
Wednesday AM   18-APR-00 16:43     4      000418 P4 ARS2 JOP83*
Thursday PM    20-APR-00 10:14     1      000420 P1 ARS1 JOP119
Friday AM      20-APR-00 15:19     4      000420 P4 ARS1 JOP119*
Friday PM      21-APR-00 13:46     3      000421 P3 ARS1 STD
Monday PM      24-APR-00 14:16     4      000424 P4 ARS1 DARKCAL
Tuesday PM     25-APR-00 09:18     2      000425 P2 ARS1 STD
Wednesday PM   26-APR-00 11:09     3      000426 P3 ARS1 STD
Thursday PM    27-Apr-00 09:36     2      000427 P2 ARS1 IL
Thursday PM    27-Apr-00 22:02     4      000427 P4 ARS1 STD
Friday PM      28-APR-00 15:23     1      000428 P1 ARS2 JOP120   
Friday PM      28-APR-00 20:28     4      000428 P4 ARS1 STD
Saturday PM    29-APR-00 08:13     2      000429 P2 ARS1 STD
============================================================

Data reformatting is complete through March 17, 2000.

We had one operations glitch on 18 April which resulted in the loss
of SXT data for the subsequent invisible orbits. Basically it was
simultaneous goofs by the SXT chief observer and the KSC tohbans.
The SXT manual has been edited to reduce the chances of the same 
mistakes happening again.

Yohkoh continues to receive one Santiago pass per day: seven listed
in the strawman schedule for week 21, which covers 15-May through 21-May.
This seems to be a good arrangement.

SCIENCE

Seminars

April 20 

V. Grechnev (NoRH): "The impulsive flare of September 17, 1999 
  accompanied by a cusp-like structure in soft X-rays"
Y. Uchida (SUT): "Accumulating observational evidence for the quadruple 
  magnetic source model of arcade flares"

April 20 

K. Shibasaki (NoRH): "Fan of rays above a flare arcade - the result of an
  interchange process"

Science Nuggets

21-Apr-00: "Oops, missed a GEM" belatedly describes an important X-class
  flare from 1998, the source of a major geomagnetic disturbance. It 
  turned out to be truly a wonderful event.

28-Apr-00: "Running in circles", the first bit of Brian's handiwork on 
  characterizing the Yohkoh orbital decay. The bottom line is that this
  series of science nuggets may become quite long...

The full list of nuggets is kept on
  http://isass1.solar.isas.ac.jp/sxt_co/index.html , 

and the current week's nugget also normally resides on
  http://isass1.solar.isas.ac.jp/sxt_co/SXTweekly.html .

PERSONNEL

No changes.

TOHBANS (spacecraft operators)

Tohbans for week 17

SOC:    S. Akiyama, Y. Saito 
KSC:    K. Fujiki, T.Morimoto
SXT_CO: B. Handy, H. Hudson
SXT_SW: - 

Tohbans for week 18

SSOC:   K. Shibasaki, T. Kobaayshi
KSC:    T. Morimoto, T. Miyagoshi 
SXT_CO: B. Handy   
SXT_SW: -