SXT Status Report
                     30 June, 1998 - 20 July, 1998
                             (Weeks 27-29)

                               H. Hudson


SUMMARY

Activity was moderate, and SXT has operated well. We have been following
the TRACE observations as well as we can, and appreciate the high-quality
TRACE mosaics that are now appearing for planning purposes.

SOLAR ACTIVITY and SCIENCE

The GOES level (see the plots, for example, on our weekly SXT Web
pages) remained between B and C, with many C flares and three M flares
during the three-week interval of this report. The science planning
has emphasized active-region structure.

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

Data archiving is complete through Week 26 (June 27).  Terminator
acquisition continues. We re-pointed Yohkoh by about half an arc minute
(July 10) to adjust for normal seasonal pointing drift. T. Kosugi and
H. Hudson had a "micro-CDAW" on the question of attitude software
optimization, which involves the HXA sensor. The decision from this
discussion was that we will experiment with pointing adjustments, and
then possibly change the on-board HXA threshold setting. 

SCIENCE

The new "science nuggets" consist of:

 4-Jul-98:   An X2 flare with an attitude
11-Jul-98:   Triple jet!
18-Jul-98:   Global coronal connectivity

These are all quite interesting, especially the 11-July one. But there is
more, please wait until you see the 25-July entry! To access the nuggets, 
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. The "Triple Jet" nugget -  built
on a Sam Freeland mini-movie - was picked up by "APOD" (the Astronomy Picture
of the Day). It's nice to know that people are making use of this material.

OPERATIONS ISSUES

   Week 27: 2 KSC passes lost
   Week 28: 6 KSC passes lost
   Week 29: 7 KSC passes lost 

The competing ISAS spacecraft now include Nozomi (the Mars mission) as well
as Akebono, ASCA, and HALCA.

VISITORS AND PERSONNEL

Many visitors have been at ISAS during this interval, partly because of the
COSPAR meeting in Nagoya. These include Dave Webb, Bob Stern and Doug
Biesecker, plus a group from MSSL (Bentley, Culhane, Wyndham). In addition,
Greg Slater and Phil Shirts arrived to install the new ISASS2 and to do many
other things. This created enough enthusiasm to allow a Ginza + Sumida River +
Asakusa + Asahi Beer Garden expedition to take place.

SEMINARS

July 2: H. Hudson (SPRC/ISAS): "TRACE movie and the 'solar magnetic carpet'"
July 9: M. Linton (Berkeley/ISAS): "Kink Instabilities and Solar Delta Spots"

TOHBANS

Tohbans for Week 27

SSOC : Yokoyama, Tsuneta
KSC  : Magara, Akiyama
SXT_CO: Hudson
SXT_SW: -

Tohbans for Week 28

SSOC : Sawa, Suematsu
KSC  : Akiyama, Shiozawa
SXT_CO: Hudson
SXT_SW: Slater, Shirts

Tohbans for Week 29

SSOC : Shimizu, Shinohara
KSC  : Shiozawa, Kumagai
SXT_CO: Hudson
SXT_SW: Slater, Shirts