SXT Status Report June 21 through July 4, 1999 (Weeks 26-27) P. Martens, B. Handy, H. Hudson SUMMARY Solar activity approached solar-maximum levels, but still with no X-class flares. SXT conducted joint observations with SOHO, TRACE, and ground-based observatories (notably Tenerife). There were no technical problems with SXT. SOLAR ACTIVITY We seem to have come near to solar maximum, judging from the high background GOES level. The average 1-8 A flux reported for the two weeks was on the order of 1.7(-6) W/m^2, about C2, and it continued unabated for the entire period. The existence of many active regions (as many as 15 NOAA numbers on June 27) meant that the activity was spread over both visible and invisible hemispheres, and could thus persist for the entire period. Interestingly, there were no X-class flare events, although 15 M-class events did occur. The largest sunspot group was NOAA 8598, at 650 millionths on June 26. OBSERVING CAMPAIGNS We concluded the first Max Millenium observing campaign, a trial run for HESSI joint observations. As organized by Canfield, Gary, and Ranns, it involved a truly huge number of observers: SXT; CDS; EIT; MDI; TRACE; OVRO (GBO); Big Bear (GBO); Mees (GBO); Siberian Solar Radio Telescope (GBO); Kitt Peak (GBO); MSFC (GBO); Meudon (GBO); Alfred University (GBO); RATAN 600 Radiotelescope (GBO); Nobeyama (GBO); Mauna Loa (GBO); Nancay (GBO); Kharkov Astronomical Observatory (GBO); Crimean Astrophysical Observatory (GBO); Mitaka (GBO); Oporto Radiospectrograph (GBO); Hiraiso (GBO); Trieste Astronomical Observatory (GBO); IZMIRAN (GBO); San Fernando Observatory (GBO); PHOENIX (GBO); Hida Solar Observatory (GBO); Ondrejov Observatory (GBO); VLA (GBO); Sac Peak (GBO); Brazilian Solar Spectroscope (GBO); Kanzelhoehe (GBO). Here "GBO" means "Ground-Based Observatory." During this period, on June 24, SXT also made observations in support of the SERTS rocket (NASA GSFC), principally a study of the DEM structures of active-region loops. The region studied was big and bright, but in fact did not make flares during the rocket flight. SXT got good data just during the rocket flight in spite of a nearly tragic operations error, but data prior to the flight were lost owing to an unfortunately timed SEU error. The rocket flight and observations were on schedule and successful. We now have a new system for tracking observing campaigns. The old system, based on "finger campaign@isass0", is now replaced by a Web-based archive system. See http://www.solar.isas.ac.jp/sxt_co/sxt_catalog.html for the record of completed campaigns, and http://www.solar.isas.ac.jp/sxt_co/sxt_future.html for scheduled ones. This latter is more like a scratch pad than an archive and can be expected to change frequently as plans mature. SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES The stray-light epoch beginning April 18 now has a complete database, including considerable offpoint data in support of the streamer campaign described in the report from the period prior to this one. Accordingly, to reduce the occurrence of dark-current artifacts from the heavily used NW limb region on the SXT CCD, we repointed Yohkoh 40 arc sec to the W on July 2. This will necessitate another full generation of stray-light database images, which we expect to take about two months. The new target sun-center location on the CCD will be [520,592]. SXT OBSERVING SEQUENCE TABLES -------------------------------------------------------- JST Day/UT Day Pass Table ID ======================================================== Tue 22-Jun-99 2 990622 P2 ARS1 DAMAX01-1 Wed 23-Jun-99 2 990623 P2 ARS2 DIMAX01-1 Thu 24-Jun-99 4 990624 P1 ARS0 SERTS-0* Thu 24-Jun-99 5 990624 P5 ARS1 STMAX01-2* Fri 25-Jun-99 2 990625 P2 ARS1 STMAX01-2 Sat 26-Jun-99 2 990626 P2 ARS1 STMAX01-1 Mon 28-JUN-99 3 990628 P3 ARS1 STMAX01 Tue 29-JUN-99 2 990629 P2 ARS2 DASTAND Wed 30-JUN-99 2 990630 P2 ARS1 DISTAND Thu 1-JUL-99 2 990701 P2 ARS1 STANDARD Sat 3-JUL-99 3 990703 P3 ARS1 STANDARD ======================================================= SCIENCE Weekly science nuggets were: 2-Jul-99: Yohkoh and TRACE (almost) co-observe an M-class flare 25-Jun-99: Yohkoh and TRACE find "moss" during the SERTS rocket flight 18-Jun-99: Yohkoh sees a beautiful arcade in the aftermath of the eruption of a giant polar crown prominence The full list of nuggets is kept on http://www.solar.isas.ac.jp/sxt_co/index.html , and the current week's nugget also normally resides on http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html . SEMINARS July 1: B. Handy (Montana State U.), "C IV Observations with TRACE" Brian has developed a technique to combine the TRACE UV observations in such a way as to make a synthetic C IV filter, whose images look strikingly different from those in the adjacent continuum. YOHKOH OPERATIONS ISSUES The mainframe computers at ISAS will be replaced, causing an outage from 11-Jul (Sun) to 15-Jul (Thu). This system is necessary for SXT table preparation, so that during this interval we will probably have to run the standard table continuously and forego calibrations. VISITORS AND PERSONNEL Piet Martens departed after a very productive visit; Brian Handy arrived to start one. TOHBANS (spacecraft operators) Tohbans for week 26 SSOC: K. Matsuzaki, H. Hudson KSC: Y. Yamauchi, Y. Hanaoka SXT_CO: P. Martens SXT_SW: G. Slater Tohbans for week 27 SSOC: S. Akiyama, S. Tsuneta KSC: Y. Yamauchi (-1), S. Yashiro SXT_CO: P. Martens, H. Hudson SXT_SW: G. Slater