3-Oct-2007

<pre>This information affects users looking at spectra from about 1.3-1.6 MeV.

A new filter has been applied to rear segment data for events falling 
between channels 4032 and 4095.  The default has the filter on for all 
rear segment high gain a2ds.  To turn it off set the control parameter, 
CLEAR_HALFSCALE to 0.
e.g.

o = hsi_spectrum(.....)
;turn off the halfscale filter which is on by default
o-&gt;set, CLEAR_HALFSCALE=0
;to turn it back on
o-&gt;set, CLEAR_HALFSCALE=1

To check it's status:
print, o-&gt;Get(/CLEAR_HALFSCALE)

The new software has been uploaded and will appear on any update after 
6:40 pm eastern today.

Richard



Following up on work started by Albert I've implemented the suggested 
filtering technique for the half-scale artifact and found that it works 
extremely well except for the first two minutes of the most intense 
event of the mission in the rear segments.

The half scale artifact appears as a band from bin 4032-4095, mainly in 
a2d 13 (det 5 rear highgain) and a2d 16 (det 8).  It was noted that 
these tend to follow uld pulses in the same segments and then further 
noted that they follow other half-scale events if not ulds.
I have a ps file showing the unfiltered and filtered peaks for each read 
a2d for each minute of 10 minutes starting at 28-oct-2003 11:06:30.  
<a href="http://hesperia.gsfc.nasa.gov/%7Erichard/halfscale_28oct2003_9det_10x1minute.ps">http://hesperia.gsfc.nasa.gov/~richard/halfscale_28oct2003_9det_10x1minute.ps</a> 


The half-scale artifact is at bin 63 in these figures.  The difference 
between the filtered and unfiltered will normally be shown as the black 
and green trace.  It's most prominent in 5 and 8


Richard
</pre>