SXT Status Report
                         1 - 15  September 1997
                            (Weeks 36 - 37)
                   H. Hudson, S. Savy, J.-P. Wuelser


SUMMARY

The new solar cycle has started in earnest, with lots of active
regions and flares. SXT worked fine throughout the interval and
we conducted several collaborative observations.

SOLAR ACTIVITY

The GOES level did not drop below B during the entire interval,
with a steady progression of high-latitude regions showing relatively
good staying power. There were 24 flares classed at C level and above.
Yohkoh has made it successfully into its second solar maximum,
apparently.

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

SXT continues to operate well. The higher activity has ended the
inclusion of long exposures in the standard observing tables. We 
have frequently readjusted the starting levels of the partial-frame
images to give the exposure control a head start. We have also begun
to include the Al.1 filter routinely in the PFI's, and find that these
new regions are bright enough to force exposure levels shorter than
the usual limit (15 sec).

There has been no further progress on the terminator (stray light
correction) program. But all the pieces are in place to make the
final improvements.

There was a missed communication between SXT_CO and the tohbans. This
has inspired us to create a new fax form that will be used in similar
cases (second table transfer to be done from KSC, rather than
Sagamihara) to prevent this from happening again. See below regarding
a possibly interesting use of the accidental data.

Data archiving is complete through Week 35, 1997.

PASS CONFLICTS AT KSC

Week 36: One pass cancelled on behalf of HALCA.
Week 37: Three passes cancelled on behalf of HALCA.

CAMPAIGNS

During Sep. 8-12 we participated in an X-ray bright point
observation scheduled also by SOHO and ground-based observatories
(L. McDonald, A. Fludra). This was a little bit unfortunate because
of the moderate activity, which kept us from doing detailed coverage
during the invisible orbits. Nevertheless SXT got excellent data on
each of the XBP's selected by SOHO. 

We also did some dedicated observation oriented towards jets.
Active-region jet activity in the past cycle was most frequently 
found in the leading parts of active regions, but the jet-active
region we tried to observe in Week 37 was the opposite. A pattern?

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

B. Schmieder and J.-C. Pecker stopped by on the way back from the
I.A.U. meeting in Kyoto, and normal research activity more or
less resumed after this grand affair.

Jean-Pierre Wuelser arrived from Palo Alto. Nariaki Nitta returned to
Palo Alto.

SEMINARS

September 5:

B. Schmieder (DASOP, Obs. de Paris): "CMEs and Prominences with
  SOHO and Yohkoh"
J.-C. Pecker (College de France): "Solar Radius Variations"

The latter talk was unfortunately not announceable prior to the
seminar, but was quite interesting.

September 11:

J.-P. Wuelser (Palo Alto): "Vector Magnetic Field Observations of the
  Footpoints of Solar Plumes
Te. Watanabe (Mitaka): "Radiative vs Conductive Energy Loss in Active
  Regions"


OTHER SCIENCE TOPICS

An operations error gave us an unusual sequence of large field-of-view
observations incorporating several full-fledged active regions as well
as the MDI high-resolution field. If anybody is interested, the
following question might be answered: What is the correlation, if any,
on time scales of minutes to hours, among distinct active regions?
This question could of course also be asked on longer time scales
by reference to the full-frame image data.



TOHBANS

Tohbans for Week 36:

    SSOC :  T. Yoshida, T. Kosugi
    KSC  :  J. Ogura, S. Yasuno
    SXT_CO: H. Hudson
    SXT_SW: -

Tohbans for Week 37:
   
    SSOC:   H. Miyazaki, T. Shimizu
    KSC.    S. Yasuno, M. Noguchi
    SXT_CO: H. Hudson, J.-P. Wuelser
    SXT_SW: -