[daip] questions about VLANT

[Eric Greisen]

Gustaaf van Moorsel writes:
 > Eric,
 > 
 > I am putting together a web page about post-processing data with
 > EVLA antennas, and I'd like to say a few words about VLANT as well.
 > A few questions:
 > 
 > 1 - Is the table with antenna corrections part of AIPS?  In other
 >      words, do people on the MNJ automatically get the latest version
 >      of that table?

     We ship tables for years 1992-2006.  The 2007 table (or any
others that the user does not have locally) are fetched from the
public ftp directory pub/VLA/baselines

 > 2 - If so, I assume I should tell users to use the latest version of
 >      AIPS since that will contain the latest antenna position correc-
 >      tions as well?

     They must have a recent copy of 31DEC07 to have VLANT at all.

 > 3 - Where is the table located, and do we intend to allow the users
 >      (read) access to the table if they so desire?

     The main tables are kept in an obscure place accessible to the
analysts and some of the rest of us.  There is a cron job that makes
sure that the public ftp site is current.

     Vivek is retro-fitting previous baseline data for the EVLA
antennas at previous stations into these files.  I will have to make
sure that the 2006 file goes out with aips MNJs.  VLANT will be fooled
by having a copy at the user's site with no way to know that it is not
current.  Note that the aips files are kept in an area that is version
independent.  So, when 31DEC07 is old, a MNJ on it will still fetch
the latest aips files.  But this gotcha is the reason that one does
not like to go back and change data in the baseline files once it has
appeared.

Eric Greisen