May 14, 2002
							   H. S. Hudson
							     

RHESSI tohban report for week starting Tuesday, May 6, 2002
(DOY 126-132, 2002)

0. Comment

I forgot that the operations meeting was on Monday, so this is late and
short. More detail next week, I hope.

1. Solar activity.

Activity was moderate, with two M-flares but no X's. 

2. Memory management

We were able to stay in A013 for most of the week, dropping out
for one day. I believe that we've had high-latitude particle fluxes
at high levels but can't quantify this at present.

3. Autonomous shutter thresholds

As a result of Sam's discovery of a pileup artifact at the A1 limit
(~25% dead) we scaled the limits back to 8% and 10% for thin and thick
shutter entry. This results in shutter motions at a much earlier stage
of a flare, for example at about C2.5 in a flare (09:50) on May 12.

This adds to the need for an improved shutter-opening algorithm. The
simplest one would be just to leave the shutter in place until the 
dead time drops to its initial value after shutter closing. In the
three cases I have looked at to date, this would have had the following
effects:

x. X-flare of April 21 (old thresholds) shutter would have skipped ten
un-needed cycles.

m. M-flare of May 11 (new thresholds) shutter would have skipped two 
cycles (out of four).

c. C-flare of May 12. No difference in behavior.

4. Coordinated observations

TRACE continues to operate at high cadence (12 s in 195) to support flare
observations.

5. General

The quicklook and state-of-health pages are available quickly now and 
are quite useful.

6. Links

http://sprg.ssl.berkeley.edu/~hhudson/tohban_links.html