Prelimiary results from the 1st LBA Calibrator Survey experiment

[Leonid Petrov <Leonid.Petrov@xxxxxxxxxxx>]

Dear colleagues,

  This morning Alessandra sent to me preliminary results of correlation v254b 
experiment, the first from the series of the LBA Calibrator Survey targeted
to the sources at delcinations [-90, -50] deg.. I could not restrain myself 
from analyzing that partial correlator output. What I saw was I so amazing 
that I thought I am day-dreaming. I scheduled 123 sources, all 123 were 
observed, and 121 have been detected. The success rate is 98.4%!!! In previous 
surveys, the success rate was in the range 60-85%.

  I did not have significant difficulties in resolving group delay
ambiguities (with spacing 3.9 ns, another world record). The only 
problem I noticed is that clock function at Ceduna shows significant
instability: http://vlbi.gsfc.nasa.gov/lcs/v254b/res+clock_all.gif
and http://vlbi.gsfc.nasa.gov/lcs/v254b/res+clock_ceduna.mopra.gif
(Clock function was bad in Parkes in the previous v230 experiment).

  The listing of the solution is accessible at
http://vlbi.gsfc.nasa.gov/lcs/v254b/v254b_prel.spl

  The source position catalogue -- very preliminary! -- is accessible at
http://vlbi.gsfc.nasa.gov/lcs/v254b/v254b_prel.cat
Only one source, 1833-772, has a dubious position.

  The formal uncertainties for declination are in the range of 1.5-2.5 mas 
for > 90% of the sources, for right ascensions * cos(delta) they are 20-80%
larger. Later I will try to apply model of the ionosphere from GPS.

  These results confirm the validity of selected strategy of observations.
I think we can stick to this scheduling strategy, except increase the 
minimum gap between observations of the same source from 1 hour to 4 hours.
This should help to improve right ascensions. Again, sensitivity is 
very important. Sources in v271a will be in general weaker.

  CERTAINLY, MORE DISKPACKS WOULD HELP A LOT.

  Chris, we promised in our proposal to make results available as soon as 
they will be correlated -- in fact we made them available even before. :-)
Feel free to provide the link http://vlbi.gsfc.nasa.gov/lcs/ to interested
parties.

Sincerely,
Leonid Petrov
25-JUL-2008 22:03:21