Re: LCS: v271a correlation is finished. Preliminary LCS1_PRE1 catalogue.

[Leonid Petrov <Leonid.Petrov@xxxxxxxxxxx>]

Dear Ed,

>    If you let me know where the aips data is (just before moving it to the
> astrometry software), I can gather some flux information and insert it
> in the table that you sent.  I don't think the u-v coverage is
> sufficient for imaging and long and short baseline correlated flux
> densities, but we can see.  Also, I suspect that the flux density scale
> may have to be bootstrapped from the known flux density of some
> sources.  With luck, the ATCA has been monitoring some of them.

   ftp://cddis.gsfc.nasa.gov/pub/vlbi/raw/mk4/2008_02_05_v254br_mk4.tar.bz2
   ftp://cddis.gsfc.nasa.gov/pub/vlbi/raw/mk4/2008_08_10_v271al_mk4.tar.bz2
   ftp://cddis.gsfc.nasa.gov/pub/vlbi/raw/mk4/2008_08_10_v271ar_mk4.tar.bz2

  Please wait for several days. Alessandra wanted to re-run Forufit 
and resubmit them. By default Fourfit discards autocorrlation. She
will force Fourfit to keep it.

   Similar to VCS, we obseved 40-50 tropospheric calibrators in each LCS 
session. For more than 70% of them X-band maps are avialble. They can be 
used for calibration.

>    Also, the accuracies are extrememly good in declination, presumable
> because the n/s baselines may be just as long as those for the VLBA. 

  The longest baseline in LBA, CEDUNA/HOBART26, is 1700 km long, and the
longest polar baseline projection (HOBART26/ATCA-104 baseline) is 1380 km.

  But keep in mind: these are FORMAL ERRORS. I did not apply yet reweighting.

> In fact, the combination of high accuracy RA's from the VLBA and DEC's
> from the LCS will be great for sources between -45deg and -30deg. 

  We can include several tens of sources in our VLBA RDV experiments.
It seems I have convinced David Gordon and Craig Walker that we can add
up to 16 sources to RDV schedules without comprommising geodetic
goals. I thought of adding 20-30 sources in declination [-40, -50] in 2-3 
RDV expriments.
  
> Finally, although the positions are absolute, I suspect they may be
> tied to about ten apriori accurate positions of high quality sources
> that were included in the run.  So, is it possible that there could be
> small offset positions in RA and, especially DEC, that are not included
> in the error estimate?

  As I mentioned, we add 40-50 previously observed strong sources in 
our LCS shcedules. This redundancy will help us to evaluate systematic
errors. But I would like to wait for three more experiments before making
a study of LCS systematic errors.

Leonid
08-DEC-2008 21:15:15