SXT/Yohkoh Report for 1-8 August 1993.
From:	L. Acton
Date:	9-Aug-93

GENERAL STATUS
     Normal Yohkoh operations continue in a gray, wet Tokyo.  There is
no change in performance of SXT.  The CCD is in excellent condition. 

CAMPAIGNS
     The Emerging Flux Region campaign with the Germans at Tenerife, the
Lockheed team at LaPalma and several other observatories in Japan and
around the world began on 3-Aug-93 and will continue through 13-Aug-93. 
Observations in Japan have been hampered by unseasonably poor weather
but a few promising joint data sets have been acquired.  So far SXT
observations have been limited to NOAA Active Region 7558. 
     A new SXT observing sequence with fixed long and short exposures is
being used in order to increase the dynamic range of the SXT movie by
forming composite images.  This technique appears to be quite successful
and is giving better coverage of the fainter active region features than
we have had before. 

CALIBRATION WORK

A. Radiation damage.
     Diffuser image made 3-Aug-92 were examined to learn the status of
x-ray damage.  There has not been an alarming change but enough new
radiation damage has been accumulated, especially at the NE limb that
Yohkoh should be repointed a couple of arcminutes to move the limbs to a
fresh area on the CCD.  This is planned for 10=Aug-93.

B. CCD dark images.
     I see no evidence of serious change in SXT dark frames--although
the overall dark signal continues to increase very slowly.

C. Straylight.
     Special "sunset" images are being acquired both with and without
the x-ray neutral density filter for calibration and correction
purposes.  It was discovered that use of the neutral density filter
greatly increases the straylight signal, although the effect on flare
observations is minor (and correctable) because the exposures are so
short.

D.  X-ray scattering from mirros.
     A special table for the purpose of collecting x-ray scatter signals
through all SXT analysis filters has been run without success because of
no flares. 

PLAN FOR WEEK 93_33
- Continue EFR campaign.
- Collect sunset images during all visible orbits.
	(This will require entries in the OP/OG loads for each day.)
- Do coronal hole temperature experiment on big coronal hole in north.
	(Many long QR FFIs in Al.1, & AlMg to add up to improve signal.)
- Continue to hope for flares to do x-ray scattering calibration.
- Upload standard dark calibration table on 10-Aug-93 at Pass 3.
- There will be no offpoint experiment this week.

PERSONNEL
     Personnel at ISAS include H. Hudson, G. Slater, L. Acton who
arrived on 1 August for 3 weeks and N. Nitta who left on Thursday.

SCIENCE
     There is much activity here as momentum builds for the Kofu
meeting.  I gave a Thursday seminar on "What does the Corona Look Like"
to focus attention on the general properties of the hot corona which is
emerging from the SXT data. 

OPERATIONS     
     Between the EFR campaign and the calibration work there were
numerous SXT table loads, and many mistakes by the SXT Chief Observer,
this past week.  At the moment (9-Aug-93) KSC is battened down to ride
out the typhoon.  The large tracking antenna cannot be used when winds
are this high.