SXT Status report
Mon, 20 January 1992
Fm: James Lemen



The past week of operations was remarkably calm compared to the previous
week (which had SEU-related troubles on 5 days in a row).  There were no
reported SXT problems and also no operational errors.  The solar
activity was also quite low for the most part, with only a few small
flares observed.  For this reason, on Tuesday we changed the Quiet
High full frame table and inserted long (15s) exposures in the thin
Al and Dagwood sandwich filters.  One change from earlier operations is
that we have decided to decrease the cadence of the 15s exposure images
compared to the 75 ms and 2.667s images.  There were many interesting
images, one set showing large expanding loops on the N-W limb - perhaps
associated with a CME.

Greg Slater and Keith Strong spend much of week working on a new SXT movie
covering about one solar rotation during the month of November.  The
movie was made using a professional M II tape recorder that S. Tsuneta
had managed to borrow.  The quality is much better than what we have
made with existing equipment.  Looking at the movie is certainly
instructive, although it is clear that the ability to alter the rate of
the playback would be highly desirable.  The movie was made by combining
the short (75 ms) and medium (2.667s) exposures from the standard Quiet
High table.  This increased the dynamic range and very adequately
removed the saturated portions of the images.  I have enjoyed viewing
the approximately 1 minute movie about a dozen times.  Each time I watch
it I see something new.

Sam Freeland arrived at the end of last week for a one week visit.  One
of his major activities will be to install a patch in the SXTE-U
on-board software will perform checksums during each CCD exposure.  This
should make it easier to track and to understand future occurrences of
SEU's.

At the Yohkoh weekly operations meeting T. Kosugi announced that a
necktie pin featuring an SXT image had been made by NEC.  These pins may
be purchased for 600 Yen (about $5).  It is not exactly specified how
these might be ordered, but if anyone reading this message would like to
purchase one or more of these tie pins, you can respond to me (J. Lemen)
and I will try to forward the list to the appropriate person.

---  End of Report  ---

From sag::ISASS0::lemen Tue Jan 21 05:48:51 1992
Date: Tue, 21 Jan 92 05:48:22 -0800
From: sag::ISASS0::lemen (James R. Lemen)
To: acton, freeland, hudson, morrison, nitta, sag::linford, slater, strong
Cc: lemen, sag::friedlaender
Subject: Short Status Report
Status: RO

Hello Everyone,

This is an abreviated status report.

1. We have decided to remove the long (15s) exposures from the FFI sequence
tables since the activity has been increasing somewhat recently.

2. Hara san ran a sequence (involving 3 table loads) today to try to get
better data to compare the various filter ratios.  He in particular
would like to gain confidence in the calibration of the 3 micron Mg
filter.

3. Sam is planning to do a patch on Thursday to provide a checksum
function during each SXT exposure.  

The instrument has continued to operate without incident for the past 11
days.

Regards,
Jim

From sag::ISASS0::lemen Thu Jan 23 02:21:08 1992
Date: Thu, 23 Jan 92 02:20:59 -0800
From: sag::ISASS0::lemen (James R. Lemen)
To: acton, freeland, hudson, morrison, nitta, sag::linford, slater, strong
Cc: lemen, sag::friedlaender
Subject: Short Status Report - SEU on 23-Jan-92
Status: RO

Hello Everyone,

This is a short status report for Fri, 23-Jan-92.

1. Today the SXT experienced another SEU between the 3rd and 4th KSC
contact.  During the 4th pass we discovered that a filter hard error had
caused the DP-J to turn off the power to the peripherals.  This causes an
"open-shutter" indication, and so Yohkoh was pointed to the east by 21
arc-min as a precaution.  During the 5th pass a checksum was performed
(with Sam Freeland in attendance) which verified that a code corruption
had occurred, indicating that the primary cause was probably an SEU.
Next, the recovering sequence was initiated, but because of a typing
error, it was not possible to complete the sequence before the end of
the pass.  The SXT is currently in a same configuration (shutter is
closed), but is not taking data.  We will attempt to complete the