SXT Status Report 28 April - 11 May, 1998 (Weeks 18-19) D. McKenzie, H. Hudson SUMMARY Activity was high, with 14 M flares and two X flares during the interval. The instrument continues to operate well. SOLAR ACTIVITY Yohkoh got many flare triggers and some splendid observations. The many flares were accompaniend by correspondingly many CMEs, and we seem to find that flares with clearly defined soft X-ray eruptive structures are more common than they had been in the last cycle. See the science nugget for May 8 for one nice example. There were many other items of real scientific interest, including a remarkable set of transequatorial interconnecting structures that participated in the ejective flare and CME of May 3, as reported in the science nugget. During week 19, we supported XBP studies led by Karen Harvey, with participation from SOHO and (yes!) TRACE. These observations were poor, by our standards, because activity was at such a high level that scattered-light background made them less sensitive than usual. Bright points were detected, but not so many - we plan to make bright points the subject of next week's science nugget, so please stay tuned. SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES Data archiving is complete through Week 16 (April 19). Terminator acquisition continues. A normal spacecraft re-pointing was scheduled May 11, about 18 arc sec to account for normal seasonal fluctuations. SCIENCE Observational work centered on the XBP campaign (JOP 082), and upon observations for JOP 059 and test exposures for JOP 080, which are concerned with signatures of coronal heating (JOP 059) and coronal and transition region dynamics (JOP 080). These JOPs are SOHO campaigns, led respectively by Robert Walsh (St. Andrews) and Frederic Clette (Royal Observatory of Belgium). More information on JOPs, including a summary of JOPs past and future, is available on the web at URL: http://sohowww.nascom.nasa.gov/~soc/JOPs/ The scheme of weekly reporting by the SXT Chief Observer on Web pages has continued, but we missed one date because of the busy joint observing schedule. The current "science nugget" is now located under the official Yohkoh Web site at ISAS, and its URL is http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html. The previous science nuggets reported by SXT chief observers are listed in http://www.solar.isas.ac.jp/sxt_co/index.html. The newer ones are: 980320.html Cavity with bright core 980327.html AR dependence of flare characteristics 980403.html Message from the back side of the Sun 980410.html Further analysis of the 7-Apr-97 flare CME 980417.html Growth and Decay of AR 8203 980424.html Proton flare, April 20, 1998 980508.html M flare ejecta and loop filling The last entry is identical with 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 we would always appreciate feedback. OPERATIONS ISSUES Week 18, five KSC passes lost to HALCA. Week 19, six KSC passes lost to HALCA. VISITORS AND PERSONNEL No personnel changes. H. Hudson was away from ISAS both weeks, but spent week 19 at the SOHO EOF enjoying an entirely different perspective. SEMINARS None. TOHBANS Tohbans for Week 18 SSOC : S. Masuda, T. Tanaka KSC : S. Ueno, K. Fujiki SXT_CO: D. McKenzie SXT_SW: - Tohbans for Week 19 SSOC : K. Marubashi, H. Watanabe KSC : K. Fujiki, H. Tonooka SXT_CO: D. McKenzie SXT_SW: -