Status Report for week ending 1 February 1992: ============================================== Instrument Operations --------------------- An error detection patch was installed last week by Sam Freeland in the SXT microprocessor. This patch checks most of the RAM code for corrupted bits including rarely used parts of the code where SEU's might have gone unnoticed before. This is a much safer way to operate the instrument, although it may result in an increase in the rate of operational interuptions. We have had two "warm reset" errors this week: Monday 27 Jan and Saturday 1 Feb (the later was detected during the 4th pass of the day and so there was no time for recovary before the sunday holiday although the instrument was confirmed to be in its usual safe state during the 5th pass). We also had a "filter soft" error which was mistakenly believed to be a more serious problem and this caused the loss of some observing time. Discussions were held between Sam Freeland and Tsuneta-san about making the recovery from these errors a series of simple OG's that would make the process more reliable and less time consuming. Otherwise the instrument has performed well providing some spectacular FFI's showing the development of a large spot region near disk center and a rapid sequence of PFI's on a limb active region that Shimuzu-san needs for his thesis. Hugh Hudson and Keith Strong improved the SXT Quiet (high) table by including more X-ray exposures so there are no long gaps between solar X-ray images and that like-filters were better paired. A second similar table was designed and loaded to include 15.108 s exposures so that SXT commanders have the choice between these sequences depending on solar conditions. A calibration sequence, which is being designed to be run regularly, may enable us to further increase our FFI full-sun cadence by reducing the number of darkframe and diffuser images taken each orbit. Discussions were held about the advisability of running long exposure X-ray images and the dangers of running SXT during SAA. The long exposures provide vital information on the nature of the quiet Sun however they may be adding to the X-ray "ghosts" seen in the diffuser images. There is a small but finite chance that if we get a flare during SAA (when there is no flare available to activate AEC) we could add to the CCD ghost problem if we also happened tobe in the process of taking several long expsoures. Currently we are running using a low cadence of 15s exposures and the SAA's are mostly during Yohkoh nights. The question remains unresolved as to whether we should operate at all during SAA. Operational evaluation has been severly limited by the lack of disk space on the SXT computers at ISAS, e.g. preventing us from looking at any DSN contact data for several weeks. The Yohkoh science bullatin board is now operational, at least in a preliminary form. Professor Uchida will be working with Keith Strong to improve its format and capabilities over the coming months. Data Analysis ------------- Greg Slater, Jim Lemen, Saku Tsuneta, and Keith Strong have continued to improve the movie of SXT FFI's from 7 November - 6 December 1991. We have added optical images, improved the colour tables, and removed cosmic ray events. We have given several demonstations of this movie to visitors from Astro-D and it has been instructive to observe their very positive reactions. The components of a movie making program have been designed to speed and improve the process based on the experience gained from the production of this one. We have had a demonstration of the Sony optical disk recorder by Hidenori Harada. It is an alternative format to the MII video tape format which we have used recently to make the SXT movie. While the optical disk seems to have several advantages (in terms of speed and flexibility) over the tape unit, it is considerably more expensive and the disks can only be written on once, making the media an expensive option. We should be able to contrast and compare them now that they are both available. Hara-san has continued his work on work on temperature measurement by SXT with input from Loren Acton and Jim Lemen. Shimizu-san has been investigating the new PFI mode data for loop flares. Several of the scientists here have volunteered to give papers at the forthcoming local science meeting at Mitaka on the 12-13 February 1992. Preparation for that meeting is in progress. Personnel --------- Sam Freeland and Jim Lemen returned to Palo Alto this week. Nariaki Nitta has been the SSOC this week with Dave Pike. Akioka-san, Hugh Hudson, and Keith Strong have been manning the SXT duties for the last week. Unfortunately Greg Slater fell ill and has spent some time in a local hospital, he has now recovered and was discharged from the hospital. It snowed heavily today making it impossible for several of our team to come to ISAS. Keith Strong 1 February 1992