SXT Status Report
                         16 Sept. - 6 Oct. 1997
                             (Weeks 38-40)
         J. Lemen, H. Hudson, D. McKenzie, S. Savy, J.-P. Wuelser


SUMMARY

Solar activity continued at an elevated level; SXT and Yohkoh continued
to operate well and there were several coordinated observing campaigns.
Alert KSC tohbans (week 40) noted that on day 2,222 of the Yohkoh
mission, image 3,333,333 was obtained!

SOLAR ACTIVITY

GOES did drop below the B level briefly during the interval, and is
headed in that direction at the end of the reporting period. There
were however four M flres, lots of C flares, and frequent CMEs.

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

SXT continues to operate well. In particular the higher level of activity,
which has included some "no flare flag" flares with extreme overexposure,
has not shown up any weaknesses in the CCD. We are planning however to
implement a change in observing policy, namely to switch off during SAA
to avoid this vulnerability to the lack of protection from the Yohkoh flare
trigger, which does not operate during SAA.

There has been no further progress on the terminator (stray light
correction) program. We note that very few SFC's were created during
September, probably a result of the rather densely filled grid we
are developing in the Al.1 stray-light correction images. Still there
is unwanted flicker in the movie - some excellent corrections, some
fairly crummy ones.

Yohkoh experienced a one-day outage (Oct. 1) because of a broken compressor in
the uplink telemetry system at KSC. It sound odd to imagine the mechanical
compression of uplink data... Luckily the breakdown occurred after the 
HRTS rocket, and the EIT cal rocket (which had been scheduled for that day)
was postponed until October 16.

Data archiving is complete through Week 36, 1997.

PASS CONFLICTS AT KSC

Week 38: Six passes relinquished in favor of HALCA and Akebono.
Week 39: Ten passes surrendered to HALCA and Akebono.
Week 40: One pass bestowed upon Akebono.

CAMPAIGNS

During Sep. 25 - Oct. 5 we participated in a coordinated observing
plan centered on Tenerife ground-based observations (B. Schmieder).

The HRTS rocket flew on Sep. 30, and Yohkoh was put into "campaign
mode" to protect the data. The launch time had been coordinated so
that in fact Yohkoh was in daylight and clear of the SAA at the time
of the flight. At present we do not have the data in hand from DSN,
nor do we know any details of the rocket flight, so we are hoping
that things went well. 

During Oct. 1 - Oct. 12 we are supporting Advanced Stokes Polarimeter
observations at Sac Peak (Pevtsov and Metcalf) trying to delineate
separator structure.

Finally, we did some special jet-hunting on behalf of M. Shimojo.
In this kind of effort we use the orbits visible at KSC to identify
a jet-active region and go there in near-real time. This is not an
easy program to succeed with, given the rarity of good jets, so we
will probably continue do as much more of this as we can. 

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

Jean-Pierre Wuelser and Nariaki Nitta returned to Palo Alto.
David McKenzie, Jim Lemen, and Greg Slater arrived.

SEMINARS

none

OTHER SCIENCE TOPICS

Sam Freeland noted a rather remarkable trans-equatorial loop system
that appeared suddenly on the East limb, and captured it on a Web movie:

   http://www.space.lockheed.com/SXT/movies/sfd_72hours.html

These loops clearly link two quite distant N and S active regions. They
will be near disk center on about October 8 and it will be interesting
to see if they show the X-point geometry we have found in earlier
trans-equatorial interacting loop systems.  This interconnecting structure
looks like it envelopes the entire active regions, rather than just 
being a subset of their loops, however. It may be familiar to LASCO C1 
observers. If it is possible, vector magnetic measurements should be
made to define the net helicities of the active regions (cf Canfield et al.
paper in the Bath proceedings).

TOHBANS

Tohbans for Week 38:

      SSOC  : S. Tsuneta & N. Saita
      KSC   : M. Noguchi & S. Sano
      SXT_CO: J.-P. Wuelser 
      SXT_SW: - 

Tohbans for Week 39:
   
      SSOC  : H. Hara & J.-P. Wuelser
      KSC   : S. Sano & Y. Iizuka
      SXT_CO: J.-P. Wuelser & S. Savy
      SXT_SW: -

Tohbans for Week 40

      SSOC  : M. Sawa & S. Kubo
      KSC   : Y. Iizuka & Y. Saito
      SXT_CO: H. Hudson & J. Lemen & D. McKenzie
      SXT_SW: G. Slater