SXT Status Report 21 August - 3 September 1995 (Weeks 34 and 35) --------- Mark Weber Hugh Hudson 4-Sep-95 I am pleased to report that ISAS (or, more specifically, the fourth floor of D-toh, in the vicinity of the SXT Analysis room) is once more abuzz with the sounds of scientists, well, buzzing. For those of you who may not recall, a mere two weeks ago I was veritably stranded here (yea, veritably). Nowadays we have three SXT Chief Observers (Hudson, Nitta, Weber), a new visitor per week (currently Ron Moore), a Hawaiian ambassador (Kevin Reardon), and our very own Lockheed Systems-Scientist (Slater). Life is good. SOLAR ACTIVITY In Week 34 the Sun mustered its resources to achieve an X-ray level of months past. AR 7901 increased its area considerably. AR 7902 managed to produce at least one C-class event; and newcomer AR 7903 also contributed to X-ray emissions. GOES data shows an obvious rise in radiation over a period of about a day. It is difficult to say if this was mostly due to the de-occultation of AR 7903 as it rose over the east limb. In the succeeding week, the first two regions set behind the west limb. General X-ray emission subsided to low levels more typical of recent times. There seems to be a continuing trend for only two or three medium-sized active regions to exist at a time within a hemisphere (east and west). SXT INSTRUMENT STATUS One of SXT's calibration issues has changed in a significant but recoverable manner. On November 13, 1992, a hole was made in the SXT aperture filter, permitting straylight to penetrate to the CCD. Calibration techniques were developed to compensate for the effect of this on SXT images. On August 16, 1995, the straylight increased by a factor of three, probably due to a further perturbation of the entrance filter. The straylight level has been stable since then, and is "still well within the range of correction". The project of adjusting the calibration process is well under way. In all other respects, the SXT has been functioning properly. CALIBRATION STATUS Currently, calibration efforts are being applied towards continuing with the various established calibration procedures, and quantifying the recent increase in the stray light. Much progress has been made in this direction in very little time. PASS CONFLICTS In Week 34 we lost a total of nine (9) passes due to conflicts with ASCA. In Week 35 Yohkoh lost seven (7) passes for the same reason. (Note: Yohkoh and ASCA are in similar orbits and both regularly lose some passes.) CAMPAIGNS = (For more information on SXT campaigns, use the following UNIX command): finger campaign@isass0.solar.isas.ac.jp - FILAMENT OBSERVATIONS (R. Canfield, et al.) This is an ongoing project "to observe filament channels and possibly catch eruptions with SXT in a configuration for good time resolution." This campaign is has been "on-hold" for the past two weeks, due to the straylight-increase discovery in Week 34, and due to Spartan preparations in Week 35. Regular communications between ISAS and Mees have been maintained. - POLAR RAY CAMPAIGN (S. Koutchmy, H. Hara) The focus is the "study of polar spikes and polar rays in coronal holes." On 25-Aug-95, SXT took PFIs of the solar north pole and low corona. This was mainly to provide a test run for SXT, and to provide some preliminary data for Koutchmy-san and Hara-san so they could further formulate their requests for SXT observations. There are currently no requests from Koutchmy or Hara for special SXT operations prior to the October Eclipse. However, some of the PFIs taken by the SXT/Spartan Tables may be of some use. - SPARTAN (L. Strachan, M. Guhathakurta) The stated purpose is "coordinated observations of the corona with the SPARTAN instruments near Ulysses N polar passage." The Spartan 201-03 launch had been scheduled for August 31. Most of the SXT Chief Observers' time in Week 35 was spent in preparation of SXT Tables for this event and in correspondence with the Spartan contacts. The Spartan 201-03 launch has since been re-RE-scheduled for September 7. The satellite will operate over that weekend. The SXT Chief Observer Corps has test-run SXT Tables prepared for the earlier Spartan schedule, and hope to view the results soon. - X-RAY BRIGHT POINTS (K. Harvey) The purpose is to "determine the spatial and temporal correspondence between XBPs and He I 10830 dark points." The proposed observing dates are 15-23 September 1995. Recent correspondence between Harvey and SXT has followed the effects of the recent straylight increase on the diagnostic filters, especially thin aluminum. SCIENCE George Roumeliotis (Stanford U.) visited in Week 34 and gave a seminar on image reconstruction for SXT. By using new tools for this purpose, he has found a rather clear example of what appears to be a loop-loop interaction. Alas for our preconceptions about this, the point of reconnection seems to be dark, rather than bright. This is consistent with the difficult time we have had in general to prove the existence of macroscopic reconnection via the SXT data, and offers a clear challenge to others to work on the difficult questions of image interpretation (including resolution enhancement) in quantitative ways. This visit was timely, because Y. Hanaoka was one of the SSOC tohbans this week. He has now written a second paper on SXT data analysis for loop-loop interactions. This made the traditional farewell sushi lunch all the more interesting! SEMINARS - The seminar for Week 34 was given by George Roumeliotis of Stanford University. The title was "IRIS: An Algorithm for the Reconstruction of SXT Images." The visual examples were impressive. - There were no seminars in Week 35. PERSONNEL - Hugh Hudson returned from a "high-energy" meeting at Goddard. - Kevin Reardon joins us at ISAS from the University of Hawaii for several weeks of (hopefully) fruitful research. - Nariaka Nitta has also come to ISAS to join the SXT Chief Observer Corps and "lend his wisdom in these trying times." Week 34 Tohban: SSOC: Y. Hanaoka and S. Ueno KSC: J. Sato and K. Hori SXT Chief Observer Corps: H. Hudson and M. Weber SXT Systems and Data Engineer: G. Slater Week 35 Tohban: SSOC: K. Shibasaki and K. Yaji KSC: K. Hori and M. Nishio SXT Chief Observer Corps: H. Hudson, N. Nitta, and M. Weber SXT Systems and Data Engineer: G. Slater