SXT Status Report 23 Apr - 30 Apr. 1995 (Week 17) --------- James R. Lemen 2-May-95 Last week I reported about the cherry blossoms. Now the azaleas are blooming around ISAS. We have created a new account on isass0 called called sxt_co = SXT Chief Observer. All messages sent to the sxt_co@isass0.solar.isas.ac.jp e-mail address will automatically be forwarded to the appropriate SXT Chief Observer. We hope this will improve communications during observing campaigns. SOLAR ACTIVITY Week 17 was an interesting week from a solar activity point of view. At the beginning of the week there X flares from AR 7864. Then as AR7863 and AR7864 rotated over the west limb, the GOES level dropped over five decades to A-level and it occasionally seemed to drop out all together. We are perhaps at one of the lowest X-ray activity times since the launch. Last week I wrote a small program that only works at ISAS to display the latest BCS spectra (the routine is called first_bcs). It is mainly used to display the temporary data that is received at KSC. Normally, one can easily see S XV spectra in fairly short integration times. However, after Ar7863/7864 rotated over the west limb it was no longer possible to discern a S XV spectrum, even with relatively long integrations (200s). This is a consistent with the fact that all active regions have disappeared from the disk. The SXT can still seem many X-ray features: bright points, and various loop systems at the east limb, and recently at the west limb and the faint remains of a active region. COORDINATED CAMPAIGNS The bright-point campaign was attempted one day this week, but it was not successful for several reasons. There were some operational difficulties at KSC and the Chief Observer failed to communicate the correct coordinates. This campaign will be rescheduled for mid-June 1995. Towards the end of the week we decided to put the SXT partial field of view on a filament target. The objective is to observe the X-ray signature of a filament eruption with better time and spatial resolution than we normally achieve with the half-resolution, full-Sun images. Kevin Reardon at the University of Hawaii is organizing the campaign and selecting the targets from Mees observations. In addition to Yohkoh and Mees, the Soon sites are collaborating under Alan Kiplinger's coordination and Big Bear is also a participant. SXT CALIBRATION The off-point terminator program continues. During the past week Hirohisa Hara determined, after consulation with NEC spacecraft engineers, the limits of the off-point maneuvers. SXT INSTRUMENT STATUS SXT continues to function smoothly and without problems. During the past week there was one bit-map error and one warm reset error. This latter error requires a manual recovery operation. YOHKOH PASS CONFLICTS We lost 7 KSC passes this past week due to conflicts with the Japanese ASCA (five) and SFU (two) missions. The operations of the IRTS instrument (Infrared) on SFU ended this week and we hope that there will be fewer conflicts with the SFU satellite. Engineering data will continue to be acquired for the next six months before the SFU is recovered by the Shuttle. SEMINARS On 26 April 1995 the seminar speakers were J. Lemen (LPARL) and Jean-Pierre Wuelser (University of Hawaii). The seminar featured two flares. Jean-Pierre spoke about the eruptive aspects of the 15-Nov-91 flare and I spoke about the 12-Jul-92 C5.3 flare. The first flare was large, eruptive, with Halpha ribbons, and the second flare was small, gradual and somewhat compact with no evidence for any eruptions (although there were plasma motions in the loop itself). PERSONNEL At the moment, the SXT team at ISAS is represented by Hugh Hudson, Jean-Pierre Wuelser, and J. Lemen. Loren Acton arrived for a one-month visit on 1-May-95 and Greg Slater will arrive on 3-May-95. Loren took over as the Chief Observer today and will continue as CO until the end of May. Week 17: Tohbans: SSOC: A. Sterling, T. Takano KSC: T. Yokoyama, A. Kubo SXT Chief Observer: J. Lemen SXT Systems and Data Engineer: (vacant -- fill in by JRL)