SXT Status Report
                     Feb. 16, 1998 - Mar. 2, 1998
                              (Weeks 8-9)

                         D. McKenzie, H. Hudson


SUMMARY

Yohkoh and SXT continue to operate well.  The major unusual scientific
activity was the observation of the solar eclipse(s) on Feb. 26. During
one of the three episodes, Yohkoh almost entered totality.

SOLAR ACTIVITY

Activity was higher than during the last reporting interval. There were
15 C-class flares reported by NOAA, the most powerful at C5.2, and NOAA
AR 8156 got to a total sunspot area of 520 millionths at its CMP on Feb.
17. For fans of solar-constant variability, this area no doubt caused
a big "dip" in the SOHO total-irradiance signal. However, from the 
high-energy point of view, activity was bland. We are waiting for giant
energetic flares to return following the first new-cycle major events
of last fall. 

SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES

A routine one-day bakeout of the CCD took place on Feb. 18. This
presented no problems. The automatic software now has the capability
of rejecting general public distribution of the bakeout images, which
look awful because the CCD is warm. In the past we didn't do this and
often had anxious e-mail messages from worried customers!

The recovery from January's entrance-filter problem is complete.
A full cycle of normal-filter correction images has been taken,
the Yohkoh pointing has been touched up by about 10 arc sec to
minimize the pointing dependence of the new corrections, and a
new cycle of ND filter correction images is now being programmed.

Data archiving is complete through Week 2 (ending Jan. 11, 1998). 

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

The last 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.

PASS CONFLICTS AT KSC (Akebono, HALCA, ASCA)

Week 8: Three passes lost to HALCA, 3 to maintenance, and 2 to a NASDA
  rocket launch.
Week 9: Four passes to HALCA, 2 to Akebono (the spacecraft). 

CAMPAIGNS

There were no special joint-observation campaigns during the past
two weeks, not counting the eclipse. For fans of these biweekly messages,
it's necessary to report that we have not properly followed up on the
very interesting expanding-loop observations reported last time (SOHO
JOP 18, led by P. Maltby). 

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

Hugh Hudson was absent Feb. 21 - Mar. 1. 

SEMINARS

J. Sato (Nobeyama): "Improvement of Yohkoh Hard X-ray Imaging"

This was derived from Sato's thesis, which encompassed several improvements
to the HXT imaging via MEM. The improvements are so great that it probably
will be profitable to go back and look at many earlier results again. This
is good news for HESSI because better results will be available to guide
the final design.

TOHBANS

Tohbans for Week 8

     SSOC :  K. AKita & J. Sato 
     KSC  :  S. Akiyama & K. Nakakubo 
     SXT_CO: D. McKenzie 
     SXT_SW: -

Tohbans for Week 9

     SSOC: T. Shimizu & N. Saita 
     KSC : S. Yashiro 
     SXT_CO: D. McKenzie
     SXT_SW: -