SXT Status Report for week ending 8 February 1992 ------------------------------------------------- OPERATIONS ---------- The week started with an earthquake (Magnitude 5.7, the largest in Tokyo for 6 years) and did not improve much for SXT operations. We attempted a recovery from the Saturday SEU problem on Monday which took several orbits. SXT seemed to run normally overnight and then an ARS anomaly (failure to select the active region in quiet-mode patrol) occurred on Feb. 4. This was traced to saturation of the morning patrol image. In addition, many filter soft errors were observed, but only in flare mode. These symptoms were found later to all result from an unintentional hard reset of SXTE-U. There was no commanding error at SSOC or KSC, nor was there an entry in the DP command log. Therefore the suspicion is that somehow an un-trapped SEU caused the reset. Two other anomalies occurred during the week, but these were both warm reset errors correctly handled by the new RAM patch. In all cases the same new standard recovery procedure was carried out. This is still being done by individual commands rather than OG's. The KSC emergency commands have not changed. No new off-pointing maneuvers have been done for additional safety (this had been done starting in early January. The BCS has also reported an increase in the frequency of SEU's recently which may be associated with the fact that Yohkoh's apogee has been coincident with the south atlatic anomally for the last two weeks. The result of these problems is that SXT has had a very low duty cycle, (about 50%) which would have been even worse if Tsuneta-san, Hugh Hudson, and Akioka-san had not come in at all hours of the day and night to man the passes and speed the SXT recovery. To further complicate things there has been a solar network problem and an error found in the FACOM code that has made data reformatting impossible and communications difficult. We have only just recently been able to look at any reformatted data since the end of January. 'Hitens' operations have reduced the number of KCS contacts for us in the coming week but the DSN were able to find three additional contacts to help maintain the continuity of the Yohkoh data. SCIENCE PROGRESS ---------------- The preparations for the science meeting at Mitaka have continued this week with Nitta-san, Greg Slater and Keith Strong all planning to give presentations. Alan McAlister has been working on an image contrast enhancement code that looks very promising for increasing our ability to see the development of the fainter features in the quiet corona while maintaining information on the flares and active region structure. The BCS team have found a few possible examples of Fe XXVI emission. PERSONNEL --------- We have a large influx of visitors from the BCS team; George Doschek, Ken Phillips, Bob Bentley and Uri Feldman are here for two weeks. Dick Canfield has joined the SXT team at ISAS for about 4 weeks. There is a very stimulating scientific environment at ISAS currently with potential discoveries and intense discussions developing regularly. Keith Strong (with contribution from Hugh Hudson) 12 February 1992