SXT Status Report 22 April 1997 to 12 May 1997 (Weeks 17-19) Hugh Hudson SUMMARY SXT continued to operate well. Solar activity was generally low but there were scattered of short-lived new-cycle regions and occasional flurries of CMEs. SOLAR ACTIVITY Low. The biggest flare was B4.3, largest sunspot group 120 millionths. The new-cycle regions seem to have taken over pretty completely. SXT INSTRUMENT STATUS SXT continues to perform well technically. Acton completed the analysis of the extended UV flood experiment aimed at understanding the behavior of the "dark pixels" seen near the limb. A further experiment will be done in mid-May. SXT CALIBRATION ACTIVITIES The spacecraft re-pointing described in the previous report resulted in a new series of terminator images via the automated system. The Yohkoh pointing errors are extremely regular and we feel that we can sharpen up the re-pointing program to get a still tighter pointing distribution. This is valuable because of the pointing dependence of the stray-light pattern - our goal is to return the thin Al images to 1992 levels of perfection via stray-light compensation. The system is so solid now that this seems almost feasible. PASS CONFLICTS Kagoshima Space Center is now operated 24 hours a day, 6 days a week, because ISAS has so many functioning spacecraft to track. There are nevertheless conflicts for use of the single 20-m telemetry dish. Those with ASCA have almost ceased because of orbital precession, and the conflicts with HALCA have also diminished. We are losing about one pass a day to AKEBONO at present: Week 17: 2 passes cancelled for HALCA, 1 for ASCA Week 18: No KSC passes were lost! Week 19: 6 passes were cancelled for Akebono. CAMPAIGNS There were several ad hoc joint observations with SOHO this week. Our general approach is to look at the Web planning page for SOHO pointing information and to follow the CDS lead. In quiet conditions, if CDS is looking at an active region or potential CME source there is usually no reason that SXT cannot use ARS0 and also follow that region. The coordination for this kind of thing is still a bit cumbersome because of the extraordinary difficulty of getting reliable network access now between ISAS and the U.S., so the next simplifying step will be to extract the SOHO planning information directly from the SolarSoft tools that are now available. 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 Loren Acton departed, but will return in May for the Solar-B meeting and some research. David Alexander departed. Serge Savy took a break for the Aussois meeting on filaments. Hugh Hudson returned from Sydney full of enthusiasm for reconnection, as long as current systems are involved. A major international Solar-B meeting took place May 6-9 at ISAS, and many foreign visitors appeared at that time, including some seldom-seen Yohkoh veterans. The general flavor of the meeting was extremely positive. Many remarkable SOHO results were presented for background information. SEMINARS There was a Yohkoh seminar on April 24: D. Alexander (LMPARL): "Turbulent Times" This talk dealt with the general questions regarding the anomalous broadening observed in the X-ray emission lines by BCS and its predecessors. It is a bit surprising, but until current work (described here) there has been no concensus on the behavior of the "non-thermal" broadenings observed in flares. It appears that systematic work with the Yohkoh BCS is straightening this situation out and may be providing an interesting new fact about flare development. TOHBANS Tohbans for Week 17: SSOC : Te. Watanabe, M. Shimojo, S. Kubo, T. Sakao KSC : S. Tanuma and K. Nakakubo SXT_CO: D. Alexander SXT_SW: - Tohbans for Week 18: SSOC : S. Hashizume, H. Hudson KSC : K. Nakakubo, S. Kawashima SXT_CO: H. Hudson SXT_SW: - Tohbans for Week 19: SSOC : K. Marubashi, S. Watari, Y. Kato KSC : S. Kawashima, S. Morita SXT_CO: S. Savy SXT_SW: -