SXT Status Report
                     Mar. 3, 1998 - Mar. 17, 1998
                             (Weeks 10-11)

                         H. Hudson, D. McKenzie


SUMMARY

Yohkoh and SXT continue to operate well.  

SOLAR ACTIVITY

Solar activity returned to an extremely high level at the end of the
reporting period, with many C-class flares and several M-class events.
Active regions at remarkably high latitudes (N46 and S40) crossed
the central meridian during week 11.

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

The recovery from January's entrance-filter problem is complete.
This was erroneously reported last time, but the final Mg/neutral
density combination finally came in during week 11. The total elapsed
time for a full cycle thus came to about 7 weeks, and all of the data
henceforth with this stray-light configuration (ie, starting Jan.
26) will be properly correctable.

The high-latitude regions pose an operations problem for SXT that
we have not really experienced before. It is now common that all
of the bright active regions simultaneously present on the Sun fit
into SXT's patrol images. That means that a flare can in principle
trigger flare mode and not be properly observed. This has happened
before, accidentally, but is to be avoided. Accordingly the SXT
Chief Observers will be making special efforts to monitor the situation
and adjust the patrol image locations as necessary.

Data archiving is complete through Week 8 (ending on Washington's
Birthday). 

We are now entering the third week of complete reliance on NASA
ground-station scheduling, and the tohbans are pleased with the
situation. Things seem to be working fine.

WEB-BASED SCIENCE REPORTS

The scheme of weekly reporting by the SXT Chief Observer on Web pages
has continued. The current "science nugget" is normally at

ftp://isass0.solar.isas.ac.jp/pub/sxt_co/SXTweekly.html

which links to this report and other pages, the previous science
nuggets reported by SXT chief observers. See index.html for access
to the following list:

971024.html  dimming
971107.html  Nov 6 flare
971114.html  Nov 14 LDE
971121.html  Movies of ejecta!
971128.html  X2.9 ejective flare
971205.html  Solar cycle
971215.html  Amazing arcade
971221.html  AR development
971228.html  Interconnection
980110.html  Global time constant? 
970117.html  Contrasting emergence 
970124.html  Data request from Ooty
970131.html  XDT rocket flies!
980207.html  Diffuse eruptive events 
980214.html  Expanding coronal loops 
980221.html  Refinement of eclipse planning
980228.html  Eclipse movies
980306.html  High-latitude active region 
980313.html  Interconnections and flares 

The latest entry is also called SXTweekly.html and contains links to
current-week operations information. We SXT chief observers seem to
like this system - it helps us make current affairs available - and
would appreciate feedback. The current one (980313 = SXTweekly right
now) is really pretty interesting, if correct - it suggests that
active-region interconnecting loops, which reflect the net helicities of
the connected regions, may change substantially during a major flare.
However please note that these reports are constructed on the fly and
are not refereed!

OPERATIONS ISSUES

Week 10: 5 passes lost due to HALCA operation and 6 passes to AKEBONO. 
Week 11: 4 passes lost due to HALCA operation and 6 passes to AKEBONO.
  
In weeks 12-14, Yohkoh will also be losing KSC contact passes due to
maintenance of the 20-m telemetry antenna. This facility is the only
link for five working satellites and is currently scheduled around the
clock, so that maintenance work will have to cut into utilization.
This is a serious matter - because of the maintenance, we failed with
the OP upload on Mar. 14 and thus lost two days' observations. 

There were no special joint-observation campaigns during the past
two weeks, not counting the eclipse. 

For details of campaign planning, see
http://www.space.lockheed.com/SXT/html2/First_Light.html
or do "finger campaign@isass0.solar.isas.ac.jp | more" from your
Unix command line. See
http://sohowww.nascom.nasa.gov/operations/targets/today 
for SoHO target planning.

VISITORS AND PERSONNEL

McKenzie returned to Bozeman.

SEMINARS

Y. Liu (Huairou/Hiraiso) "Observation and Extrapolation of 3D
  Magnetic Fields"

This was especially interesting in the context of the forthcoming
CDAW, to take place April 6-10 here at ISAS. The central theme of
this CDAW is to make use of joint data sets to track the field
connectivity between corona and photosphere in a variety of contexts.

TOHBANS

Tohbans for Week 10

     SSOC :  T. Yoshida, H. Hudson
     KSC  :  M. Ohyama
     SXT_CO: D. McKenzie/H. Hudson
     SXT_SW: -

Tohbans for Week 11

     SSOC: K. Shibasaki, Y. Liu
     KSC : Te. Watanabe 
     SXT_CO: H. Hudson
     SXT_SW: -