[daip] Change in CVEL

[Eric Greisen]

Mark Reid wrote:
> Eric W Greisen wrote:
>> Mark Reid wrote:
>>> ear Designated AIPSer:
>>>
>>>    One of our group (Xu Ye) recently noticed that the 2009Dec31 and 
>>> 2008Dec31 versions of CVEL report different channel shifting when run 
>>> on the same VLBA data set.   Has there been a recent change?
>>>
>>> Mark Reid
>>>
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>>> Daip at listmgr.cv.nrao.edu
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>>>   
>> Yes but the difference should be very small if any.
>>
>> Eric
> 
> Attached are two runs of CVAL (2009 and 2008 versions) on the same data 
> set.  The differences are about 0.7 channels, where a channel was 
> 4MHz/256=15 kHz, and the observing frequency was 12.2 GHz.

Craig reminded me that the AN file for VLB arrays has changed geometry 
from left-handed in 31DEC08 to right handed in 31DEC09 (after 20 Sept).
If the student is applying CVEL in 08 and 09 to exactly the same data 
set then the 08 version has incorrect antenna coordinates and will not 
realize that.  Note that 09 automatically updates the AN file if it 
finds a left handed system.  PRTAB will show extra keywords in 09 
including XYZHAND = 'RIGHT' and extra columns for antenna diameter and 
effective beamwidth.

ERic Greisen