SXT Status Report 12 May, 1998 - 1 June, 1998 (Weeks 20-22) D. McKenzie, H. Hudson SUMMARY Activity dropped through a local minimum, with several days hovering near the B1 GOES level. There were no technical problems with SXT; the STT software was re-installed. SOLAR ACTIVITY Despite the low activity in mid-May, regions on the W limb turned on and there were many flares in week 22, culminating with an LDE on May 31. We have now identified the origin of this event to have been not in one of the W limb regions, but on the SE instead. Another remarkable set of transequatorial interconnecting structures appeared, and are the subject of the current "science nugget" at http://www.solar.isas.ac.jp/sxt_co/980529.html. This nugget addresses the question raised in an earlier trans-equatorial observation, http://www.solar.isas.ac.jp/sxt_co/971227.html. During week 20, SXT took part in SOHO JOP 080, making fast-cadence PFIs of an active region. This JOP was designed to take advantage of EIT's shutterless-operation mode, in which EIT can make images at a higher-than-normal cadence (16 seconds). Instruments taking part in the JOP included SXT, EIT, TRACE, MDI, CDS, SUMER, HAO, and La Palma. Also during week 20, SXT took part in SOHO JOP 059, making PFIs of a number of active regions to support CDS study. During week 22, SXT supported AR studies led by Karin Muglach, with participation from SOHO and TRACE. For the latter, this is part of a two-week "staring" observation on a single active region, AR 8227 (central meridian passage on approximately May 31). This series of observations has led (May 30) to some active-region jets well-observed by SXT. We've made numerous efforts to observe jets in this manner, normally unsuccessful, so this is quite nice. We expect that the TRACE data on these jets will be beautiful! SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES Data archiving is complete through Week 19 (May 9). Terminator acquisition continues. A normal spacecraft re-pointing was scheduled May 18, about 24 arc sec to account for normal seasonal fluctuations. The idea is to hold the long-term drift to about 20 pixels peak-to-peak NS, and 10 pixels EW. SCIENCE The three current "science nuggets" pretty much show it all: 15-May-98: Observations by a flotilla of S/C 22-May-98: Filament Channel seen in Multiple Wavelengths 29-May-98: Connecting Structure Between Distant Active Regions To access these, go to http://www.solar.isas.ac.jp/sxt_co/index.html As usual, the current week is also on http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html. This shows the weekly SXT operations report as well as a GOES plot indicating the Yohkoh data currently available on line. OPERATIONS ISSUES Week 20: 8 passes were lost due to conflicts with Haruka Week 21: 6 passes were lost to Akebono. Week 22: no passes were lost to conflicts. From now on, through the launch on July 4 and probably a bit beyond, we will experience some operations conflicts at KSC on behalf of PLANET-B (on to Mars!). Launch countdown begins at 15:00 JST on July 3, culminating in launch at 03:30 JST. Yohkoh may get no KSC passes these two days. After launch, KSC will act as a backup antenna station for the critical operations phase, so Yohkoh may have to give up a few passes each week until November. VISITORS AND PERSONNEL H. Hudson was away from ISAS at the end of the month for AGU/SPD. Greg Slater and Phil Shirts visited for a week to give software support. SEMINARS None. TOHBANS Tohbans for Week 20 SSOC : A. Sterling, T. Miyagoshi KSC : D. Sasaki, H. Tonooka SXT_CO: D. McKenzie SXT_SW: G. Slater, P. Shirts Tohbans for Week 21 SSOC : Y. Liu, M. Shimojo KSC : H. Hara, D. Sasaki SXT_CO: D. McKenzie SXT_SW: - Tohbans for Week 22 SSOC : M.Miyashita, K.Ichimoto KSC : M.Kasahara, H. Hara SXT_CO: D. McKenzie SXT_SW: -