from:	 Young, Ken 
to:	 Mark Gurwell 
cc:	 "Primiani, Rurik" ,
         Jonathan Weintroub ,
         Eric Keto ,
         Nimesh Patel ,
         Chunhua Qi ,
         Lars Kristensen ,
         David Wilner ,
         Qizhou Zhang ,
         Sridharan Tirupati Kumara ,
         Jun-Hui Zhao ,
         Alice Argon 
date:	 Thu, Dec 5, 2013 at 10:25 AM
subject:	 SWARM Correlator Test Track - When did the music stop?
mailed-by:	 cfa.harvard.edu
Dear SWARM Data Aficionado,

   We know that secondary fringe rotation stopped on the SWARM 
correlator sometime during our test track.   The question is when.   
I think we had fringe tracking until very near the end of the track; 
I think is stopped at around UT 17:24 (the track ended around 18:13).   
The first plot attached below shows the pseudo-continuum built 
from SWARM for Orion BN/KL. I would claim that there's a very clear 
detection throughout the time we looked at that source (the second 
plot shows the SWARM spectrum, with strong lines clearly detected).   
These plots are both just from baseline 2-5, our shortest baseline.   
Had secondary fringe rotation not been occurring on that baseline, 
the phase would have gone through a full wrap every 30 seconds or so 
(please note that the fringe rates I sent yesterday were 50% too high - 
my software that produced that table had a gunn multiplier of 3, 
but it should have been 2).I think the continuum plot shows we were 
not wrapping phase every 30 seconds (the scans were 10 second scans).    
The next sources were IRC+10216 and 0854+201. SWARM did not 
convincingly detect either of those sources. But they may have been 
too weak. The third attached plot shows the SWARM spectrum of IRC+10216, 
and no lines are seen. The 4th attached plot shows the IRC+10216 
spectrum from the upper 2 GHz of the legacy correlator, and it too 
saw no strong lines in the region covered by SWARM (although there 
is a strong line seen outside of the overlap region). We had not done 
pointing for a long time, the weather was very poor, and I think we 
just didn't have a strong enough signal to detect on IRC+10216 and 0854+201.    The last source we observed was 3C279. The last attached plot shows 
the pseudo-continuum built from SWARM for the 3C279 scans. It looks 
like we were detecting it until around 17.4 on that plot.That's when 
I think we lost fringe rotation on SWARM (although maybe it was going 
again for a couple of minutes before we stopped - Rurik, 
did you restart it?).

Taco

to Ken, Mark, Jonathan, Eric, Nimesh, Chunhua, Lars, David, Qizhou, 
   Sridharan, me, Alice
Hi Taco,

Thanks for figuring this out. I believe I did in face restart
fringe-stopping before we stopped.

Best,
Rurik
	
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