[daip] Re: Request for including the GMRT as one of the array in UVFIX.

[Eric Greisen]

I have been taking a look at UVFIX at a deeper level than simply
having a code for the center position and recognizing that it is not
VLBI.

It appears that the SU table and header list EPOCH or EQUINOX as 0.0
and intend by that that the coordinates and u,v,w are based on
apparent coordinates of date.  UVFIX should then precess to mean
coordinates in J2000 and correct the u,v,w to that convention as well.
(Currently the epoch 0 causes the task to assume that the coordinates
are 1950.0 which is wrong.)

I have a version that appears to be working excpet for a "minor"
problem - the u,v,w values I get are all of opposite sign from those
that come with the data.  Is it possible that your Bx, By, Bz are of
opposite sign?  Or is the baseline direction conventions (and the
visibility phase) of the opposite direction from the VLA?

The Delta Bx we use is Bx(2) - Bx(1) where 2 is the higher numbered
antenna and 1 the lower numbered antenna.  Should UVFIX be reversing
all phases, cross-hand polarizations, etc?

Eric Greisen