Report from ISAS

                      29 August - 4 September, 1994
   			    Marilyn Bruner   


SUMMARY

	Solar Activity increased this week with the appearance of A/R 
7773.  The planned filament observing campaign had to be abandoned, as
the brightness of 7773 in X-rays was too high to permit the long exposures
required for filament observations to be safely made.  Most of the
week was spent in observing 7773 in the normal ARS1 mode with a 2x2 Observing
Region.  Two M class flares were produced by this region, one of which was 
observed by Yohkoh.
	
OPERATIONS

This week's operation went very smoothly, with only minimum problems.  On two
occasions, we changed the observing plan to delete the long exposures from 
the observing sequence for part of the week when the sun was found on Pass 1
to be more active than expected.

Starting Sept. 1, HXT was put in "spectroscopy" mode (actually
a modified calibration mode). During this period any flare trigger
initiates telemetry with 64-channel energy resolution, but
correspondingly reduced time resolution. There is an impact on
SXT in post-flare quiet telemetry. This week there was one test
case, but it occurred at the end of the orbit so there was no
impact at all. The chief observer will keep an eye on the situation.
The new mode of operation of HXT is valuable and will remain in place
for an undetermined period of time, probably until at least one
good flare is caught this way. 

SOLAR ACTIVITY

	Active region 7773 has been quite productive of flares, producing 
two M class flares and over 30 C class events.  Many were observed by SXT, 
but a frustratingly high percentage seem to occur when Yohkoh is in eclipse.
Most PFI observations have been of this region, using a 2X2 ROI at full
resolution.  The region appears to be magnetically complex; many different 
loops are visible in soft X-rays and are constantly appearing and 
disappearing.  On Friday and Saturday, a new active region appeared at
the E Limb; its surface brightness was equal to 7773 at times, though its
total area is still smaller due to foreshortening.

	There is a well-developed filament channel extending from about 
N 30 E 15 degrees to about N 10 W 15 degrees.  A filament occupying part
of this channel is visible in both H-alpha and He II 10830.  A second arcade
of soft x-ray loops, located at about W 20 and oriented in a N-S direction
may define a second filament channel.

	The N polar crown filament has re-formed, and is visible in H-alpha
on the W limb at about N 60.  There is no visible x-ray emission at the N
pole, but the S pole is now obscured by faint emission on the Earth-side
of the sun.  The NE quadrant is occupied by a large coronal hole.

PERSONNEL

	Marilyn Bruner assumed the duties of Chief Observer, and Nariaki Nitta
returned to Palo Alto for a well deserved rest.  Jean-Pierre Wuelser
arrived to begin a one-month stay.  Mukul Kundu continued his work with Nitta
and Hudson.  Many of the senior Japanese staff have departed for a meeting
in China, leaving the analysis center sparsely populated.

PLANS

	We plan to spend next week checking observing sequences for 
use in the SPARTAN 201 mission, originally scheduled to begin on 13 September.
Our tentative plan is to make a series of deep FFI exposures with the
spacecraft off-pointed in the direction favorable to the SPARTAN coronagraph
observations.  Our understanding of the Current SPARTAN plan is to observe
along four different radii, dwelling at each roll position for about 10
hours.  This plan may change, and we will adapt our plans accordingly.

	A major scientific objective of the SXT observations is to determine
the coronal structure in the intermediate region above which ground-based
observations become difficult and below the inner radial limit of the SPARTAN
instruments.