SXT Status Report November 23, 1998 through December 14, 1998 (Weeks 48-50) H. Hudson, M. Weber SUMMARY Solar activity was high, capped by an X-class flare on Nov. 28. There were no technical problems for Yohkoh or for SXT. SXT conducted some coordinated observations with TRACE, SOHO, and the VLA. SOLAR ACTIVITY The GOES background flux ranged between B and C (see the weekly plots on our "science nugget" Web pages at http://www.solar.isas.ac.jp/sxt_co/index.html). There were several X-class flares, bringing the total thus far in the rise phase of this cycle to 13, of which 3 have happened during this reporting period. OBSERVING CAMPAIGNS There were no formal coordinate campaign observations during the interval, but we have continued our close cooperation with SOHO, TRACE, and the VLA whenever possible. We continue to have routine confusion when it comes to target selection - there is no really good system for the instruments we're most interested in (CDS, TRACE, the VLA) to exchange near-real-time pointing coordinates and observing sequences with Yohkoh. We continue to work on this problem. For example, in a response to queries from the SXT Chief Observer, the TRACE planner agreed to start sending weekly operation plans by email again. SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES All functions have been normal. We adjusted the Yohkoh "normal pointing" on Dec. 5 to maintain the best configuration for terminator correction images. Our test of success - the quality of the corrercted composite Al.1 images - continues to improve, so we are doing the right thing. SXT OBSERVING SEQUENCE TABLES ----------------------------------------------------------------- JST Day UT Time Pass Table ID ================================================================= 22-NOV-98 21:07 3 981122 P2 ARS1 DARKCAL 23-NOV-98 16:16 1 981123 P1 ARS1 DIFF 23-NOV-98 21:24 4 981123 P4 ARS1 STD 25-NOV-98 20:14 4 981125 P4 ARS1 STD 26-NOV-98 17:06 2 981126 P2 ARS2 CDS 26-NOV-98 20:31 4 981126 P4 ARS1 STD 28-NOV-98 14:14 1 981128 P1 ARS2 PFI DOM 28-NOV-98 17:39 3 981128 P3 ARS1 STD 30-Nov-98 19:55 4 981130 P4 ARS1 DARKCAL 1-Dec-98 17:58 4 981201 P4 ARS1 STD 2-Dec-98 13:37 2 981202 P2 ARS1 DIFF 2-Dec-98 17:02 4 981202 P4 ARS1 STD 4-Dec-98 17:36 4 981204 P4 ARS1 STD+LONG 5-Dec-98 14:27 3 981205 P3 ARS1 STD 7-Dec-98 23:59 4 981207 P4 ARS1 DARKCAL 8-Dec-98 00:16 4 981208 P4 ARS1 STD 9-Dec-98 19:25 2 981209 P2 ARS1 DIFF 10-Dec-98 00:33 5 981209 P5 ARS1 STD 11-Dec-98 18:15 2 981211 P2 ARS2 STD+VLA ===================================================== SCIENCE The main scientific activities in the SXT group at ISAS have circulated around flare studies (Hudson, Khan, Nitta) and solar rotation (Kubo, Weber). We attempted to report on the new-cycle X flares to the San Francisco AGU meeting, but did not succeed because of the AGU registration bureaucracy! We found that all of these large flares showed ejecta when our observations were complete enough. The new standard flare table, in place since mid-1996, includes good wide-field coverage. See the science nugget for Nov. 27 for an overview of the X-flare data. The northern hemisphere, away from active regions, displayed some puzzling and noteworthy phenomena - see the science nuggets for Dec. 4 and Dec. 11. In fact, please check out all or any of the recent weekly science nuggets embedded in the SXT operations reports: 11-Dec-98 Confused arcade? 4-Dec-98 Skinny arcade or fat jet? 27-Nov-98 The X flares of the new cycle 20-Nov-98 Hideous daily difference image 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's nugget is also always kept on http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html. SEMINARS Dec. 3, 1998: K. Hori (Nobeyama) "Study of Solar Decimetric Bursts with a Pair of Cutoff Frequencies" M. Weber (Montana State U.) "Differential Rotation in the Soft X-ray Corona" Dec. 10, 1998: K. Shibasaki (Nobeyama) "Ballooning Instability" S. Kubo (ISAS) "Solar Rotation Period of the Soft X-ray Corona" Note that during these two weeks, we were privileged to hear from at least half of the world's leading experts in the interpretation of solar rotation via soft X-ray imaging! OPERATIONS ISSUES No particular issues. On the occasion of visitors from JPL, we (Sterling and Hudson) generated some statistics regarding the NASA telemetry support activity, bridging the 1997-1998 interval which includes both DSN and Wallops management. The DSN utilization dropped at the time of the handover (February 1998), which was anticipated, but we were surprised to find that Yohkoh does not seem to be utilizing Wallops as efficiently as we should - instead of about 30 dumps per week, we're averaging about 22. Much of this shortfall is apparently due to our scheduling procedures at ISAS, so we will attempt to tighten these up for future operations. VISITORS AND PERSONNEL Lidia van Driel-Gesztelyi departed. Nariaki Nitta departed. We now understand white-light flares a lot better. TOHBANS (spacecraft operators) Tohbans for week 48 SSOC : J. I. Khan, M. Weber KSC : S. Yashiro, T. Yokoyama SXT_CO: N. Nitta SXT_SW: - Tohbans for week 49 SSOC : M. Yamaguchi, K. Hori KSC : T. Yokoyama, H. Sekiguchi SXT_CO: N. Nitta, H. Hudson, M. Weber SXT_SW: - Tohbans for week 50 SSOC : N. Kobayashi, S. Tsuneta KSC : H. Sekiguchi, Y. Nakagawa SXT_CO: M. Weber SXT_SW: -