SXT Status Report
                      16 June 1997 to 7 July 1997
                             (Weeks 25-27)
                          S. Savy, H. Hudson 


SUMMARY

SXT continued to operate well. Solar activity was low, with only one
C-class flare observed during the interval.

SOLAR ACTIVITY

The largest sunspot area reported was only 40 millionths, and there were 
just five GOES events listed (including the C1.1 on 30 June in AR 8057).
  A quite remarkable streamer bottom was observed on June 21 (E limb) and
July 5 (W limb): it had a bright X-ray sheath around the cold filament and  
an exceptionally well-defined cavity, bulging outwards in a manner 
reminiscent of the celebrated 21 Feb 1992 flare event.  Acton comments
in e-mail that this looks just like one of B.C. Low's models.
  A re-visit to Acton's analysis of the total SXT signal level confirms
his conclusion that SXT saw its lowest levels in about June 15, 1996, +- 
one month, but the current lull could conceivably create a second
local minimum.

SXT INSTRUMENT STATUS

SXT continues to perform well technically.  
  Yohkoh suffered from typhoon assaults both on Tokyo and Kagoshima,
with some loss of data (four contact passes).
  The D-toh analysis facility was rearranged during Greg Slater's tenure
as software guru. The video players are now more conveniently located on
a rack, the LPS17 printer is now adjacent to isass0 and isass1, and some
substantial amount of space in the "big room" has been made available.
  The network connection from ISAS to the US had essentially ceased. It
has gotten much worse in the past few weeks, and ftp transfers are 
routinely failing. The chief observers cannot use the Internet for
planning observations. Prof. T. Mukai of the space plasmas group is
looking into the situation.

SXT CALIBRATION ACTIVITIES

We continued to try to sharpen up the Yohkoh pointing in an effort to
improve the stray-light database.
  The Yohkoh pointing was touched up on June 18, in order to keep the
terminator images near the center of the distribution of pointing
values. There is still a small problem with the database software for
the Al.1 terminators, but we're working on it.

PASS CONFLICTS

Week 25: Two passes were cancelled for HALCA
Week 26: One pass was cancelled for HALCA

CAMPAIGNS

There were joint campaigns with SOHO (polar jets, JOP057) and with
the VLA (jets and loops). SXT also followed SOHO target pointing where
possible, especially the CDS field of view.

For Yohkoh target planning, the SXT weekly observing plan is available on
the Web at
        http://www.space.lockheed.com/SXT/html2/First_Light.html
or with
        "finger campaign@isass0.solar.isas.ac.jp | more"        .

See http://sohowww.nascom.nasa.gov/operations/targets/today"
for SoHO target planning.

VISITORS AND PERSONNEL

Many of the U.S. Yohkoh team members went to Bozeman, Montana, for
the SPD meeting, leaving only Savy and Khan (BCS) in D-toh.
No personnel changes among SXT personnel; Lee McDonald (BCS) returned
to the U.K. but will be back soon.

SEMINARS

(June 19)

L. Culhane (MSSL) "'X-ray Astronomy' from Yohkoh - studies
  of low surface brightness features in the corona"

  One of the key results of Yohkoh SXT is gradually taking shape - what
can the coronal temperature distribution tell us about the heating 
mechanism(s)?

K. Hori (NAO) "Ca XIX line profiles of solar flare loops in 1D hydrodynamic 
  simulations"

  The discussion of this presentation was quite rewarding because so
many people with explicit research interests in flares, BCS, and simulations
were present. One key question remained unanswered - why hasn't anybody
tried this kind of modeling before?

TOHBANS

Tohbans for Week 25:

    SSOC :  Takano, Weber 
    KSC  :  Watanabe(H), Imai 
    SXT_CO: Hudson 
    SXT_SW: Slater 

Tohbans for Week 26:

    SSOC :  Miyazaki, Yoshimura 
    KSC  :  Imai,     Ueno 
    SXT_CO: Savy 
    SXT_SW: Slater

Tohbans for Week 27:

    SSOC :  Torii, Sakao
    KSC  :  Ueno, Yashiro
    SXT_CO: Savy
    SXT_SW: -