Report from ISAS. (9/30/91) L. Acton It is now one month since Solar-A launch. As of 1816 JST on 9/30/91, SXT has logged the following number of operations [Thanks, Mons, for looking this up.]: Aspect door moves 38 Filter wheel A moves 13620 Filter wheel B moves 18412 Shutter exposures 38052 The vast majority of these exposures are "scientifically usable" as Sam Freelend says--and a good fraction are downright exciting. We have observed a 4 sec duration x-ray flare in a single pixel and an enormous arcade of expanding coronal loops following a filament eruption at disk center (Sadly, we did not observe the eruption itself.) We have a good example of pre- explosive phase heating in a loop (flare at one footpoint) and examples for which it looks like the action is up in the corona. Some of the most amazing surprises are large scale, both dark (absorbing?) structures and marvelously complex shapes (waves?, moving fronts?). Almost none of these data are definitive or just what we'd want for various reasons but they point the way to improving our technique and demonstrate the crucial importance of the ground based data--little of which we have seen yet [but many thanks, Hal, for the on-line H-alpha pictures]. As far as I know, the satellite Yohkoh and its scientific instruments are performing correctly. The pointing and stability have improved markedly--although it will probably always be necessary to reregister sequences of images [something we haven't gotten around to yet]. As we knew all along, x-ray flares are brutally difficult to observe, although we have made a lot of progress at preventing overexposure. However, a properly exposed flare kernel means loss of virtually all of the fainter surrounding structure because of the enormous intensity differences. Thank goodness we have a very low scatter telescope or we'd really have trouble seeing what is going on. Tadashi Hirayama was here Saturday evening looking at images with us and he concluded that the aspect telescope is in focus. Marilyn Bruner's design and hard work have paid off handsomely, it seems that it IS possible to build and achieve orbit with a fixed focus instrument which is in focus. My deep and hearfelt appreciation goes out to the good folks at MSFC and HQ who madae it possible for us to do the White Sand focus andfunctional calibration. Magnetic plage (faculae) show up very well in the 30 angstrom filter at 4308 angstroms. We do about as well as could be expected with a 5 cm telescope and 2.5 arcsec pixels. We have not yet compared coalignment at the arcsec level (this cannot be done until we have mastered the use of spacecraft attitude information) but it is darn close to perfect. By the standards of the SKYLAB era our data analysis capability is phenomenal. Even I, a computer dummy, can make useful scientific evaluations and conclusions on data that is only a few hours old. We expect to be able to be much more efficient as the "official" data analysis software comes on line in a couple of weeks when Sam and Tim show up. Our thanks go out to Dave Stern for his I(nteracative) D(ata) L(anguage). It is a fabulous tool for science. Spacecraft and experiment operations are pretty difficult and taxing. We non-Japanese speakers are of relatively little use. The command generation and performance evaluation software is reasonably straightforward to use even though somewhat cumbersome and labor intensive. It runs, however, on a wonderfully mysterious main frame system based on big IBMs that is almost beyond me to penetrate. After several lessons I can make my way through the many necessary steps but if ever I inadvertantly press a wrong key I am lost! My Stetson hat is off to my Japanese colleagues who have mastered this system. As it is, a great deal of scientist time must be spent doing work that computers can and should be doing faster and with less chance of error. We hope to be able to fairly easily move the labor intensive instrument health monitoring activities to the workstations in an automated mode. The preparation of improved tools for command generation may take a bit longer. We had the SXT/Yohkoh press conference today downtown at the Ministry of Education. About 10-15 reporters and one TV crew showed up and there was intense questioning about solar science and what the x-ray picture meant. As all of the hour long interview was in Japanese I could only follow in a vague way but it was clear that the scientific quality of interest on the part of the press was very good. Sadly, the effort to reproduce quality prints from the color negative Tim Roethig and the others worked so hard to produce in time failed over here so the press was handed color hard copies made by Saku on his color printer, in the dead of night, as replacements. They were not of the same qualilty but, at 150 dpi, weren't too bad either. I hope that the folks at NASA HQ were able to make use of the LPARL images. Now that a month has passed we are preparing to turn on the CCD thermo- electric cooler (TEC). This is about the only SXT function left to activate and test out. Dark signal is not as much of a problem as we had anticipated but it is hoped that the TEC will bring the CCDS dark spike population fully under control. The appearance of cosmic ray or energetic proton signals in our images outside the SAA is rare. However, there are times, when I presume that Yohkoh is passing through the SAA, when the images get quite freckled and some rather long streaks appear. It may be difficult to do quantitataive work with these pictures but the ability to follow a flare evolution or changes in coronal structures is not seriously degraded. Mike Finch has arrived this evening to help us get organized--we can use a bit of this. I want to go look at some images, so, sayonara. Loren W. Acton