SXT OPERATIONS STATUS REPORT FOR WEEK ENDING 22 FEB 1992 -------------------------------------------------------- OPERATIONS ---------- SXT operations continued to go smoothly over this last week with more no SEU's. Hugh Hudson and Nariaki Nitta have maintained the monitoring of the SXT during real time contacts and to aid the SXT toban. The Sun has few active regions on it at present with the complex that produced a large flare rotating over the west limb and a new complex appearing over east. Hugh Hudson and Keith Strong adjusted the optical exposures in the two active FFI tables to allow for the decrease in sensitivity in the optical channel. The calibration table has been researched and will be available next week, but in the mean time some of the calibration exposures have been replaced into the FFI tables instead of the 15 s Al 1400 and DAG filter exposures. At the weekly operations meeting several issues were discussed. George Doschek gave an overview of the results of his visit to ISAS, which were impressive. He has looked at several SXT exents chosen on he basis of good BCS data. He and Uri Feldman are convinced that the morphology of most big flares are the same, namely a single hot bright loop with most of the hot plasma being at the apex of the loop. They are now seeking the equivalent HXT data to see how that fits into this picture. We reported some of the discussions about SXT table modifations to the ops meeting and this trigered a wider debate on how Yohkoh can better plan joint observations. Keith Strong volunteered to head a subcommittee of all the experiment teams to plan this important task more thoroughly and report back to the ops meeting in the near future. The state of archiving was discussed and we outlined Mon's plan to the meeting. It was generally thought it was a good idea to start the archiving the data on exabyte tapes without the spacecraft pointing. It was agreed that we should have the FACOM available overnight during the catchup period but that may need consultation with others. Watanabe-san reported that the idea of copying the tapes using the PC system that they had counted on had been abandoned so the BCS team may need to use the archiving tape drives to make their copies when not in use for archiving. KSC reformatting and tape copying will be a toban duty from now on. We also had a very productive SXT meeting on Thursday with Tsuneta-san, Shimizu-san, Hugh Hudson, Greg Slater, Nariaki Nitta, and Keith Strong. We discussed several outstanding issues. Operations during SAA are still considered a problem although there is no eveidence that any damage has occured as a result of doing so and the benfits are manifest. While we will continue to operate in this manner but we identified a need for regular evaluation of the diffuser images and tracing any new features back to their origin. Other modes of operation are equally dangerous and so we need to monitor more deligently how well the SXT is picking up the flare site, for example. These are the sorts of tasks that the operations team does not have time to do in the current intensive environment and so we proposed asking short-term visitors to take on these evaluation tasks in future. So Dick Canfield was assigned the first of these tasks which was to evaluate the GOES/SXT calibration and see if there is any X-ray degradation to match the optical degradation. We discussed option about the CCD warmup test. While warming the CCD by 40 C may be dangerous there seemed less reluctance to turn the TEC off. Tsuneta-san will discuss these options with Loren Acton during his vist to California next week and then put a concensus plan forward to Ogawara-san on his return. We also had a lengthy discussion about what level to train short term visitors and 3 month visitors so they can relieve more of the burden on the 5 SXT super tobans. No conclusion was reached but we must do something to ease their operational burden. SCIENCE PROGRESS ---------------- Apart from the work that Feldman and Doschek reported, Ken Phillips has been working on the temperature changes seen in very impulsive flares, where it seems the Fe XXV temperature can change by as much as 5 MK in about 15 seconds. This implies much higher densities than was previously thought to be the case. Dick Canfield has continued to work on the 15 November flare with some facinating results. J-P Weulser has put together a series of overlay movies with include various combinations of H-alpha, soft X-rays, HXT images and magnetograms. This event shows a large amount of H-alpha and X-ray ejecta which react very differently. Comparison of the evolution of the HXT images compared to the magnetic field revealed that there were two "footpoints" visible early in the onset phase of the flare that were located well away from the evental flare site. PERSONNEL --------- We have had many visitors this week. On Monday we hosted about 100 high school teachers, showing them the SXT movie, flare images, recent data and BCS spectra. They seemed duely impressed but asked some remarkably penetrating questions. Hugh Hudson and Ken Ohki gave the commentry and Greg Slater, Bob Bentley, and Keith Strong gave the demonstartions. Later in the week Bob Rosner visited ISAS and discussed our data at length. He gave us some interesting insights to the data based on his Skylab experience. On Saturday a large group of the Astro-D experimenters came to see the Yohkoh data and were given a tour by Tsuneta-san and Greg Slater. Keith Strong 23 Feb 1991