SXT REPORT FOR WEEK 3: 10-16 January 1993 ========================================= General Status -------------- Much of this week's activities were covered in Loren's final report so I will omit some of the items that he has already mentioned. SXT continues to work well and, although the Sun has been relatively quiet, we continue to get facinating data. We have lost some KSC passes to the Akebono satellite due to a problem with its ground station. SXT has now taken over 850,000 images of the Sun in its first 16 months of operations. Our lives have been made interesting by an extended period of heavy, cold rain in the Tokyo area. Many of us here felt the large earthquake in northern Japan; it was a gentle rocking motion that seemed to go on for a minute or more. No damage to equipment or people here although there was considerable damage and injuries near the epicenter. Personnel --------- Loren Acton left ISAS after a 1-week stay, and is replaced as Chief Observer by Keith Strong. Greg Slater and Nariaki Nitta also joined the operations team this week. Dick Canfield has come to ISAS for a month. Dave Pike from RAL is also visiting ISAS. The SSOC Tobans were A. McAllister, H. Hara, and K. Ichimoto. The KCS Toban was S. Masuda. Solar Activitiy and Interesting Events -------------------------------------- There was an M flare on 13 Jan which Yohkoh caught the peak and early decay. It was on the SW limb and we have a spectacular series of partial frame images of the high arcade that was formed as a result of the flare. There were at least 20 C-level flares during this period but we wont know how many of these were seen by Yohkoh until all the data is in from DSN and reformated. On 14 Jan SXT observed a revealing loop evolution on the SE limb. The loop appeared initially with two sharply angled bends in it between the two active regions that it spanned. It was over 50,000 km high. As the loop steadily grew, the loop top first becomes more rounded and then square. The loop top then developed a series localized kinks that grow as the loop dispersed into a complex of interleaved flux tubes. SXT Operations -------------- Loren and Keith made a number of minor changes to the SXT tables to return SXT to normal operations after Bob Lin's balloon flight ended. We shortened the period at the begining of each orbital day that we use for the UV flood so as to increase the available observing time. We are preparing for support of next week's flight of a grazing-incidence soft X-ray telescope built by Dan Moses. We have also opened discussions with Leon Golub for the support of the flight of his NIXT payload in March 93. We have a number of instrument health and calibration exercises to do in the near future. These include a repeat of the sucessful CCD bake out and regular repeats of taking diffuser images. We will be designing a table to help us understand the scatter patern seen across the CCD in long exposures during flares and another to obtain full resolution dark frame images to help interpret full-resolution partial frame images. Persuing an interesting discovery of soft X-ray spikes, coincident with the hard X-ray burst, at the footpoint of flaring loops by Hudson, Dennis, and Strong, we will try to design a table to optimize the SXT PFI flare tables to take the highest-possible-temporal-resolution images of the flare. When these sequences have been thought through they will presented to the Monday Operations meeting for discussion. Masuda-san alertly found an anomalously short exposure for a nominally 30-s image (i.e, 26 s). The origin of this problem still seems to be a mystery, although Tsuneta-san has pointed out many different ways that an exposure can be terminated without loss of the image especilly during a real-time contact, which is when this occured. No other examples have been found before or since. At the moment we do not consider this to be a problem. The quick look data has been plagued by missing lines of data. The problem is understood now to be in the ground software and is being fixed. The final reformatted data has no such problem. Our thanks to the computer experts here at ISAS for finding time to work on this problem when they are already busy many other tasks, such as preparations for the launch of ASTRO-D. Keith Strong, 16 January 1993