SXT Status Report 15 May - 28 May 1995 (Weeks 20 & 21) --------- Loren W. Acton 28-May-95 Two very successful weeks for science. On the 15th of May SXT had an ideally successful cooperation with the NASA/GSFC Solar Extreme-ultraviolet Rocket Telescope and Spectrograph (SERTS) experiment. Last week we had the joy of seeing the tremendous use being made of SXT data at IAU Colloquium No.153 (Magnetodynamic Phenomena in the Solar Atmosphere -- Prototypes of Stellar Magnetic Activity). Tomorrow (actually today) I will return to Montana and Nariaki Nitta will take over as SXT Chief Observer. SOLAR ACTIVITY The SERTS investigators were incredibly lucky! At the time of their launch a nicely developed complex of activity centered around AR7870 was perfectly situated for their spectrograph. This region produces some beautiful sequences which should help illuminate problems of the formation of active region interconnections and neutral line arcades. As the region rotated off the disk the GOES level returned to the A range and we have resumed quiet coronal studies. I've personally become fairly hopeful that we may be able to detect the signature of the chromospheric network in coronal emission or temperature. We shall see. QUIET SUN OBSERVING A special table designed to optimize use of SXT observing time was run for 4 orbits on 28-May. More than 1 hour of PFI observing was accumulated through the AlMg filter and over a half hour in the Al.1 filter -- intermixed with a dark frame about every 5th cycle through the table. This program produces excellent data for quiet corona studies but can only safely be run when the x-ray level is at Low-B or A levels because the shutter remains open essentially all of the time. SXT INSTRUMENT STATUS The SXT instrument continues to operate without any problems. What a champ the Yohkoh spacecraft with its payload of instruments has been! CALIBRATION STATUS New software has been written to permit better understanding of what terminator images, taken between 25 and 10 seconds before sunset and used for straylight correction, are most needed. Nitta san will now use these new tools to specify additional spacecraft offpoint commands and to guide the terminator program. We have several serious gaps in the terminator image data base which need to be filled. Now that the sun is so quiet SXT's automatic region selection is chasing CCD dark spikes again. These data are not useless because they tend to go to the same dark spike in the north east and can be summed together for quiet coronal studies. It is possible that the system can be better optimized -- another job for the SXT Chief Observer. The other option is to use fixed pointing during times when the Sun is very quiet. Because of other demands on Morrison san's time the improvement in SXT dark frame correction has not yet been completed. It is planned to use dark frames formed by averaging as many dark images as possible to improve statistics for work with faint signals. An orbit phase correction will also be applied. SEMINARS On 10 May 1995 the seminar speakers were Alan McAllister, a Yohkoh alumni presently at HAO, and Hugh Hudson. The press of time prevented our imposing on M. Aschwanden, B. Schmeider, V. Gaizauskas, M. Kundu and other distinguished visitors for seminars -- but good scientific discussions around the video monitor and workstations were enjoyed by all. PERSONNEL Week 20 Tohbans: SSOC: Wakabayashi,Y.,Yoshimura,K. KSC: Yuda,S.,Kato,Y. Week 21 Tohbans: SSOC: Y.Kato and T.Ishii KSC : H.Miyazaki and H.Hara SXT Chief Observer: Acton, L. SXT Systems and Data Engineer: Slater, G.