[daip] Newsletter article for comment

[Jim Ulvestad]

Hi Eric et al.,

This looks okay.  One addition I would make at the very end,
add the following sentence:

>From within the 31DEC01 version of AIPS, typing "RUN VLBAUTIL"
followed by "HELP VLBAUTIL" will give a list of the procedures
and a one-line description of each.

Eric, it turns out that newsletter contributions are due to
Betty today, can you make any suggested changes (from me
and others) and then forward to Betty.  Also, it should
have some set of names signed at the bottom--either yours
or yours and Amy's or yours and Amy's and mine.

jim

Eric Greisen wrote:
> 
> New VLBA/VLBI Calibration Procedures in AIPS
> 
> For the past year the AIPS group has been developing procedures to
> simplify the reduction of VLBA data and, in many cases, other VLBI
> data as well.  These procedures are contained in the RUN file VLBAUTIL
> available in the 31DEC01 release of AIPS.  They include procedures to
> load, ``fix'', calibrate, and examine data, up to and including fringe
> fitting.  Using these procedures, it takes only a few hours to take a
> typical twelve-hour continuum phase-referencing experiment from
> loading to imaging with most of the time being spent loading the data
> and fringe fitting.  These procedures not only simplify the inputs to
> tasks, but run the variety of ``bookkeeping'' tasks that need to be
> performed for a calibration step.  For example, the fringe-fitting
> procedures fringe fit and then apply the calibration by looping
> through the sources.
> 
> The procedures can be separated into three categories: procedures that
> should be run for all experiments, special case procedures (multiple
> subarrays, multiple frequencies and polarization data), and data
> examination procedures.  In the first category there are procedures to
> load, remove redundant calibration tables, determine a-priori
> amplitude corrections, determine instrumental phase corrections, and
> fringe fit the data.  The special case procedures will find subarrays,
> copy different frequencies to separate files, fix polarization
> labelling, correct parallactic angles, and calibrate cross-polarized
> delays.  To examine data there are procedures that print the antenna
> and scan information for the experiment, plot the calibration tables
> verses time, and plot the cross-correlation spectrum.
> 
> For a detailed description of all the procedures, see AIPS
> Memo No. 105, "AIPS Procedures for Initial VLBA Data Reduction",
> by Ulvestad, Greisen and Mioduszewski available at the AIPS web site:
> http://www.cv.nrao.edu/aips under documentation.