SXT Status Report
                  April 3, 2000, to April 17, 2000 
                            (Weeks 15-16)

                         H. Hudson, L. Acton


SUMMARY

Activity was moderate; we've been helping with SOHO JOP083, which
struck it rich with AR8948; SXT has had no technical problems.

SOLAR ACTIVITY

There were 9 M flares in this interval. There are many active regions, for
example 15 on April 4, but no huge ones and no X-class flares. We have been
watching for special targets, according to the new system of alerts 
detailed on http://isass1.solar.isas.ac.jp/sxt_co/alerts.html.

OBSERVING CAMPAIGNS

Yohkoh ran special tables supporting VLA observations on April 2 and 
April 8, and for the full period covered here, supported SOHO JOP083.
This normally meant ARS2, initially with an obscure region but finally
with AR8948 (CMP April 10), which then became quite active. It produced
two of the M flares, for which we hope that comprehensive (eg TRACE)
data now exist.  The JOP targeted microflares but...  we all know that the
more of them there are, the more of the big ones there are too.

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

Small problems - little Y2K bugs continue to occur and be squashed. The 
transition to a new normal pointing location (from about Feb. 11) is 
now virtually complete, and the Al.1 movie images look quite nice.
During Acton's visit to ISAS, he continued to work on the problems
associated with the aperture filters. Hudson began work on documenting
the effects of pointing jitter at the sub-major-frame level.

SXT OBSERVING SEQUENCE TABLES

-------------------------------------------------------------
UT Date & Time                    Pass    Table ID
=============================================================
Monday          2-Apr-00 19:12     1      000402 P1 ARS2 VLA+JOP83
Tuesday         4-Mar-00 00:28     4      000403 P4 ARS2 JOP83+DK*
Wednesday       4-Mar-00 19:31     1      000404 P1 ARS2 JOP83+DF*
Wednesday       5-Mar-00 00:38     4      000404 P4 ARS2 JOP83*
Thursday        5-Mar-00 21:24     3      000405 P3 ARS2 JOP83*
Friday          6-Mar-00 23:16     4      000406 P4 ARS2 JOP83*
Saturday        7-Mar-00 21:44     4      000407 P4 ARS2 VLA+JOP83*
Sunday          8-Mar-00 18:30     2      000408 P2 ARS1 STD*   
Tuesday AM     10-APR-00 20:32     4      000410 P4 ARS1 JOP83+DK*
Wednesday AM   11-APR-00 15:35     1      000411 P1 ARS2 JOP83+DF*
Wednesday AM   11-APR-00 20:42     4      000411 P4 ARS2 JOP83*
Thursday AM    12-APR-00 14:04     1      000412 P1 ARS2 JOP83*
Saturday AM    14-APR-00 17:47     3      000414 P3 ARS1 STD*
Saturday PM    14-APR-00 12:50     1      000415 P1 ARS2 JOP83
Sunday AM      15-APR-00 17:56     4      000415 P4 ARS1 STD*
============================================================

SCIENCE

Seminars

April 13

S. Akiyama (ISAS): "High-temperature regions above flare loop tops"
S. Watari (CRL): "The interplanetary disturbance during 1999 Feb. 18-19 
  associated with an interconnecting loop structure"

Science Nuggets

31-Mar-00: "The Inscrutable DEM" shows a pretty picture and then launches
  into a turgid discussion of DEM in Withbroe solar-wind models. With lots
  of line plots, this is not the most exciting science nugget, but... we
  need to be quantitative about things! For real non-experts, DEM stands
  for "differential emission measure."

7-Apr-00: "Solar variability" contrasts the nature of X-ray variations
  ("the Sun as a star") with those in white light ("the solar constant").

14-Apr-00: "Sigmoid creationism" documents the interesting pattern by which
  an active-region sigmoid structure became illuminated during a flare. The
  region in which this happened was the JOP083 target region, so we should
  also be able to study this process with TRACE high-resolution data.

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

TOHBANS (spacecraft operators)

Tohbans for week 15

SSOC:   K. Akita,     M. Sawa
KSC:    S. Kawashima, R. Kano
SXT_CO: H. Hudson, L. Acton
SXT_SW: - 

Tohbans for week 16

SSOC:   S. Watari, H. Hudson 
KSC:    R. Kano, Fujiki  
SXT_CO: H. Hudson 
SXT_SW: -