SXT Status Report October 12, 1998 through November 9, 1998 (Weeks 42-45) D. McKenzie, H. Hudson SUMMARY Activity began low but then became quite high. There were no technical problems for Yohkoh or for SXT. SXT conducted some coordinated observations with TRACE and ground-based observatories. TRACE is retiring for the eclipse season! SOLAR ACTIVITY The GOES background flux, ignoring flares, (see the plots, for example, on our weekly SXT Web pages at http://www.solar.isas.ac.jp/sxt_co/index.html) rose to the C level at the end of the reporting period. Superposed on this were some large flares, approaching the X level, including a swarm of extremely rapid events reaching C levels. In one of the latter we discovered a repetitive jet, interesting because soft X-ray jets in flares are harder to see than those in XBP sources. This jet is featured with other marvels in our Week 45 science nugget (see below for the URL). OBSERVING CAMPAIGNS The SPARTAN subsatellite was launched Nov. 1 and observed for its nominal two days, this time with telemetry (!) and on Nov. 2 the SOPHIE sounding rocket also made coronal observations. We tried to follow the schedules as best we could, but of course Yohkoh cannot observe the distant corona easily. So we emphasized observations of streamer bases and trans-equatorial interconnecting loops (the W limb showed a striking example on Nov. 1-2, and we obtained a time series of full-resolution observations. The analysis may shed more light on the origin of these structures, whether by reconnection or birth, or both, and the SPARTAN observations could be crucial even though largely at higher altitudes. SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES We redefined the normal pointing for Yohkoh (Oct. 27) to allow for seasonal and secular drifts in the normal pattern. We still have not yet implemented Acton's suggestion of _anticipating_ these drifts, so we have to keep a sharp eye out for changes. See the "quick functional performance" pages on ftp://isass0.solar.isas.ac.jp/pub/sxt_co/quick/quick.html for details if you're an expert. A routine bakeout of the CCD took place Nov. 5-6. Detailed results from this await the P.I.'s attention, but the "quick" pages show that the exercise did not cause any problems. The integrated dark current dropped by a tiny but perceptible amount as a result of warming the CCD. This time we avoided circulating warm images, ie those with predominantly dark current, and we have gotten no panic messages from observers fearing that SXT had possibly degraded. A major flare happened during the bakeout sequence and was partially observed in flare mode. The flare mode ARS function may have behaved erratically because of the large dark signal, but it's reassuring that even with a warm CCD, excellent flare images can be obtained. We probably already knew this from the last solar maximum! SXT OBSERVING SEQUENCE TABLES ----------------------------------------------------------------- JST Day UT Time Pass Table ID ================================================================= 21-Oct-98 08:28 UT P2 "981020 P4 ARS1 DARK+TRACE" 22-Oct-98 10:26 UT P2 "981022 P2 ARS1 DIFF+TRACE" 23-Oct-98 09:01 UT P2 "981023 P2 ARS1 STD" 24-Oct-98 09:18 UT P2 "981024 P2 ARS1 STD" 26-Oct-98 08:09 UT P2 "981026 P2 ARS1 STD" 27-Oct-98 08:26 UT P2 "981027 P2 ARS1 DARKCAL" 28-Oct-98 07:00 UT P2 "981028 P2 ARS1 DIFF" 29-Oct-98 05:35 UT P1 "981029 P1 ARS1 STD" 31-Oct-98 06:08 UT P2 "981031 P2 ARS1 STD" 02-Nov-98 03:17 UT P1 "981102 P1 ARS2 SPAR1" 02-Nov-98 04:59 UT P2 "981102 P2 ARS2 SPAR2" 02-Nov-98 06:42 UT P3 "981102 P3 ARS2 SPAR3" 03-Nov-98 01:52 UT P1 "981103 P1 ARS1 SPAR4" 03-Nov-98 05:16 UT P3 "981103 P3 ARS1 SPAR5" 4-NOV-98 02:08 1 981104 P1 ARS1 DIFF 4-NOV-98 05:33 3 981104 P3 ARS1 DARKCAL 5-NOV-98 00:43 1 981105 P1 ARS1 BAKE 6-NOV-98 04:23 3 981106 P3 ARS1 STD 7-NOV-98 02:57 2 981107 P2 ARS1 STD SCIENCE An international science meeting sponsored by the Nobeyama Radio Observatory took place in Week 44, and most of the SXT CO personnel attended with pleasure. The weekly science nuggets embedded in the SXT operations reports consisted of: 23-Oct-98 An anniversary sigmoid/halo CMEE 30-Oct-98 A fine tracery of hot loops 6-Nov-98 Sideways Ejections The URL's for these and for the full list of science nuggets can be found on http://www.solar.isas.ac.jp/sxt_co/index.html, and the current week is also always kept on http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html. SEMINAR There were two ISAS seminars during this period: (Oct. 21) T. Yoshida (NAO) "Emission measure" Application of different techniques for fitting three-filter SXT observations with parametrized DEM curves, either linear in log space or quadratic. The results differ from those obtained with the normal filter-ratio technique. (Nov. 5) B. Schmieder (Obs. de Meudon), "New Perspectives on Solar Prominences" As the title implies, she spoke of the problems involved in understanding prominences in 3D, emphasizing the wonderful work in Aulanier's thesis. OPERATIONS ISSUES No particular issues. The Yohkoh operations meeting discussed the Leonids problem Nov. 2 and will do so again on Nov. 9 (shower arrives Nov. 17). McKenzie is tracking the predictions, and the most recent information suggests that the fluence may not be so great as originally advertised. At the time of writing, it appears that SXT will operate normally, but that Yohkoh high voltages may be turned off or reduced just in case. VISITORS AND PERSONNEL Phil Shirts and Dick Canfield arrived. Visitors "passing through" included Markus Aschwanden, Nicole Vilmer, Silja Pohjolainen, and Brigitte Schmieder. TOHBANS (spacecraft operators) Tohbans for Week 43 SSOC : Nakakubo, Ishizaki KSC : Kouzu, Morimoto(-10/22) SXT_CO: McKenzie SXT_SW: - Tohbans for Week 44 SSOC : Miyashita,Akiyama/Shimojo/Takahashi KSC : Kozu(-27)/Torii(-3),Hata SXT_CO: Hudson, McKenzie SXT_SW: Shirts Tohbans for Week 45 SSOC : Sakao, Canfield KSC : Hata(-8), Ohyama SXT_CO: McKenzie SXT_SW: Shirts