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%Body of intermediate AIPSletter for 30 June 2021 version

\documentclass[twoside]{article}
\usepackage{graphics}

\newcommand{\AIPRELEASE}{June 30, 2021}
\newcommand{\AIPVOLUME}{Volume XLI}
\newcommand{\AIPNUMBER}{Number 1}
\newcommand{\RELEASENAME}{{\tt 31DEC21}}
\newcommand{\NEWNAME}{{\tt 31DEC21}}
\newcommand{\OLDNAME}{{\tt 31DEC20}}
\newcommand{\THISYEAR}{2021}
\newcommand{\NEWYEAR}{2022}
\newcommand{\OLDYEAR}{2020}

%macros and title page format for the \AIPS\ letter.
\input LET98.MAC
%\input psfig

\newcommand{\MYSpace}{-11pt}

\normalstyle

\section{Happy 42$^{\rm nd}$ birthday \AIPS\ and FITS,  news}

The FITS format was devised in a meeting at the VLA site on March 27
and 28, 1979.  Don Wells (then of NOAO) and Eric Greisen (still of
NRAO) were the primary authors while Barry Clark and other NRAO staff
members provided valuable suggestions.  The FITS format, enhanced by
later extensions, is still in wide spread use in astronomy and is the
envy of other scientific fields.  Then the FITS format colored the
design of the \AIPS\ internal formats.  The \AIPS\ project was begun
officially on July 1, 1979 and has stood the test of time remarkably
well.

Due to the outbreak of the COVID-19 pandemic, the NRAO went to
``infectious disease operating status'' on March 16, 2020.  Telescope
operations (other than ALMA) continued with a skeleton support staff.
The rest of us were expected to work as best we could from home.  On
June 8, 2020 we began the first steps to return to the new normal.  It
has taken us another year to begin the process of return to full
operations.  Fully vaccinated employees may return to their offices and
use meeting rooms with no masks.  Limited outside user visiting is
allowed as of July 1 if fully vaccinated.

Robert Phillips writes {\it ``I've just done (what appears to be) a
successful AIPS install on a M1 Mini (running macOS 11.2.3); the only
thing I had to do was tell it that the architecture wasn't MACPPC (but
MACINT), and have the Rosetta2 translation layer already installed (at
least, I'm assuming that's part of it, since it was already
installed).''}  A native port to the M1 will have to wait until I have
access to one and until there is a gfortran for it.

Your editor does find times when he would like interesting things to do.
If you find any problems with \AIPS\ or have any suggestions for new or
improved functions, please do not hesitate to e-mail me at {\tt
  daip@nrao.edu}.

\subsection{\Aipsletter\ publication}

We have discontinued paper copies of the \Aipsletter\ entirely, at least
for this issue.  The \Aipsletter\ will be available in PostScript and
pdf forms as always from the web site listed above.  New issues will be
announced in the NRAO eNews mailing and on the bananas and mnj list
server.

\subsection{Current and future releases}

We have formal \AIPS\ releases on an annual basis.  While all
architectures can do a full installation from the source files,
Linux (32- and 64-bit), and MacIntosh OS/X (Intel) systems may install
binary versions of recent releases.  Binary versions for Solaris and
MacIntosh (PPC) are available for the {\tt 31DEC17} release but not
for later releases.  The last, ``frozen'' release is called \OLDNAME\
while \RELEASENAME\ remains under active development.  You may fetch
and install a copy of these versions at any time using {\it anonymous}
{\tt ftp} for source-only copies and {\tt rsync} for binary copies.
This \Aipsletter\ is intended to advise you of improvements to date in
\RELEASENAME\@.  Having fetched \RELEASENAME, you may update your
installation whenever you want by running the so-called ``Midnight
Job'' (MNJ) which copies and compiles the code selectively based on
the changes and compilations we have done.  The MNJ will also update
sites that have done a binary installation.  There is a guide to the
install script and an \AIPS\ Manager FAQ page on the \AIPS\ web site.

The MNJ for binary versions of \AIPS\ now uses solely the tool {\tt
  rsync} as does the initial installation.  For locally compiled
(``text'') installations, the Unix tool {\tt cvs} running with
anonymous ftp is used for the MNJ\@. Linux sites will almost
certainly have {\tt cvs} installed; but other sites may have to
install it from the web.  Secondary MNJs will still be possible using
{\tt ssh} or {\tt rcp} or NFS as with previous releases.  We have
found that {\tt cvs} works very well, although it has one quirk. If a
site modifies a file locally, but in an \AIPS-standard directory,
{\tt cvs} will detect the modification and attempt to reconcile the
local version with the NRAO-supplied version.  This usually produces a
file that will not compile or run as intended.  For local versions,
use a copy of the task and its help file in a private disk area
instead.

\AIPS\ is now copyright \copyright\ 1995 through \THISYEAR\ by
Associated Universities, Inc., NRAO's parent corporation, but may be
made freely available under the terms of the Free Software Foundation's
General Public License (GPL)\@.  This means that User Agreements are no
longer required, that \AIPS\ may be obtained via anonymous ftp without
contacting NRAO, and that the software may be redistributed (and/or
modified), under certain conditions.  The full text of the GPL can be
found in the \texttt{15JUL95} \Aipsletter, in each copy of \AIPS\
releases, and on the web at {\tt http://www.aips.nrao.edu/COPYING}.


\section{Improvements of interest in \RELEASENAME}

We expect to continue publishing the \Aipsletter\ approximately every
six months, but the publication is now primarily electronic.  There
have been several significant changes in \RELEASENAME\ in the last six
months.  Some of these were in the nature of bug fixes which were
applied to \OLDNAME\ before and after it was frozen.  If you are
running \OLDNAME, be sure that it is up to date; pay attention to the
patches and run a MNJ any time a patch relevant to you appears.
There are number of new tasks and verbs in \RELEASENAME.  They include
{\tt DGAUS} to correct a model visibility file made with a Clean image
for the Clean beam, {\tt IANTB} to produce an {\tt ANTAB} file from the
{\tt GC} and {\tt TY} tables, {\tt VBRFI} to compute statistics from
autocorrelation data, {\tt PLRFI} to make plots from the text file
written by {\tt VBRFI}, and {\tt SHAHO} to flag hollography data for
shadowing.  Several new tasks to process VLBA data using files not
included in the standard FITS-IDI file are currently being tested.
These will be used to help study issues found in RDBE data.  The new
verbs are {\tt TVBANDW} to perform several black-and-white enhancement
schemes and {\tt TVDATA} (also called {\tt TVFACTS}) to remind the user
of the parameters of the TV display.  A pipeline {\tt RUN} file was
developed to study RFI at the VLBA\@.

{\tt 31DEC20} contains a change to the TV display program {\tt XAS} that
makes it incompatible with previous releases when characters are
displayed.  {\tt 31DEC14} contains a change to the ``standard'' random
parameters in $uv$ data and adds columns to the {\tt SN} table.  Note,
however, that the random parameters written to FITS files have not been
changed.  Older releases of \AIPS\ cannot handle the new {\it internal}
$uv$ format and might be confused by the {\tt SN} table as well.  {\tt
  31DEC09} contains a significant change in the format of the antenna
files, which will cause older releases to do wrong things to data
touched by {\tt 31DEC09} and later releases.  You are encouraged to
use a relatively recent version of \AIPS, whilst those with recent VLA
data to reduce should get release \OLDNAME\ or, preferably, the latest
release.

\subsection{VLBI}

\subsubsection{RFI monitoring}

It is intended that we should monitor RFI at the VLBA sites.  To support
this, a data reduction pipeline {\tt RUN} file called {\tt VLBARFI} was
created.  It is based on {\tt VLBARUN} but is aimed to provide
calibrated autocorrelation output data sets.  It executes the new task
{\tt VBRFI} to determine statistical parameters of these data.  {\tt
  VBRFI} writes out a detailed text file containing the mean spectra
and rms divided by mean spectra for each antenna.  The maximum, minimum,
and mean of these spectra over all scans is written and may be plotted.
Another new task, {\tt PLRFI}, was written to read the text files to
make the same plots, should they be needed at a later time.

The full scheme for archiving and accessing such data remains to be
developed.

\subsubsection{Miscellaneous}

\begin{description}
\myitem{VLBARUN} was changed to allow for systems in which {\tt convert}
   is known not to work.  In this case, PostScript plots are copied to
   the {\tt OUTFILE} area and the output html does not look for gifs.
   {\tt UVPLT} now uses {\tt IMSIZE} so the procedure has to reset that
   adverb after every {\tt UVPLT}\@.  The title line in the output html
   was corrected.  The option to omit the EOP and/or TEC steps was
   added.  The EOP correction could cause the script to fail if the data
   set is very recent.
\myitem{ACIMG} was changed to make an {\tt ANTENNA} axis rather than
   combining all included antennas into one image plane.
\myitem{IANTB} is a new task that writes an {\tt ANTAB}-format text file
   from the system temperature ({\tt TY}) and gain curve ({\tt GC})
   tables.
\end{description}

\subsection{Display, imaging, and analysis}

\subsubsection{Remote TV display}

During the work from home period, users may be required to access their
office computing facilities over a VPN connection.  The \AIPS\ TV
display can still work with {\tt tv=local} causing the {\tt XAS} window
to be displayed through the internet on the home computer.  This tends,
however, to be rather slow.  The ``hold'' function in the TV allows the
calling routines to tell the TV to hold any updates and then to release
all updates to the display.  This was changed to count the number of
hold on commands and hold off commands and to update the screen only
after all ons are turned off.  A new command to force the update
ignoring the counts was added.  Numerous tasks were revised to leave
the menu display on during more of the operations.  Numerous hold
operations were changed to reduce the display update operations.  Minor
changes in function, setting boxes for example, have been noted.

\subsubsection{TV enhancement verb changes}

A new enhancement verb, called {\tt TVBANDW}, was added to do
enhancements in black and white.  Button A does step wedges with the
number of wedges controlled by the cursor X position.  Button B selects
a sine wave function with the cursor X position controlling the starting
intensity and number of sine waves.  Button C selects a stair step
transfer function with the cursor X position controlling the number of
steps.  In all case, the cursor Y position controls a ``gamma''
correction.

The circular color scheme in {\tt TVPSEUDO} (Button B) was changed so
that the cursor X position controls the starting color and number of
loops (reduced to a maximum of 3).  The cursor Y position controls
alternatively the saturation and brightness of the colors.  This
extra control allows the colors to be more or less garish.  The verb
{\tt TV2COLOR} has a new second coloring scheme with the two colors
separated by 1/2 of a turn in hue.  The cursor X position selects
the central point separating the two colors and the Y position controls
the saturation of the colors.  Button A changes the colors by 1/12 of a
turn, button B switches between constant intensity and step wedges, and
button C switches to the initial coloring scheme.

The standard default scaling of the LUT and OFM transfer functions was
adjusted slightly.  Also the actual value range of image loads to the TV
was expanded by 0.5\%\ to avoid having a non-blank pixel always be
black.

\subsubsection{Boxcar smoothing}

Previously all boxcar smoothing operations in \AIPS\ were symmetric with
weight 0.5 at the edges.  Thus a boxcar of width 2 was in fact a Hanning
smooth.  This has been changed so that even widths are not symmetric and
all points in the boxcar have equal weight.  Reference pixels are
adjusted to compensate for this asymmetry.  This change was not made for
the application of channel-dependent calibrations to avoid a shift in
the bandpass.

\subsubsection{Miscellaneous}

\begin{description}
\myitem{DFTPL} now allows $x$-axis parameters elevation, hour angle,
    LST, parallactic angle, and azimuth as well as the previous
    parameter time.
\myitem{TVDATA} is a new verb to remind the user about the size of the
    TV display window, number of channels, scaling range at the various
    steps in making the display, and the current graphics plane colors.
\myitem{TVFACTS} is another name for {\tt TVDATA}.
\myitem{CCMOD} was given a new model type which is the product of a disk
    and a Gaussian.  The Moon multiplied by the primary beam is an
    example of a source needing this model.
\myitem{IMAGR} now shows the number of iterations and current Clean flux
    on TV residual images even when there is only one facet.  Certain
    formats were changed to provide more digits when appropriate.
\myitem{PBCOR} now also allows Gaussian and polynomial beam shapes.
\end{description}

\subsection{UV-data}

\subsubsection{Calibration models}

Images may be used in source modeling in \eg\ {\tt CALIB}, although
Clean images, due to the convolution by the Clean beam, will not match
the data at larger spacings.  CASA, however, provides model images that
have not been convolved.  It was discovered that the computation of the
model from an image only worked correctly when the reference pixel of
the image was precisely centered.  This has been corrected by a rewrite
of the low level routine used to place the image in a rather larger,
zero-filled array.  Another change was made to allow the image models to
be scaled by the IF-dependent total fluxes entered in the source ({\tt
  SU}) table.

{\tt UVSUB} may be used to make a $uv$ data set of a source model.  When
that model is computed from a Clean image, the longer spacings are
reduced in amplitude by the Fourier transform of the Clean beam.  {\tt
  DGAUS} is a new task which may be used to correct the model data set
for this issue.  It is to be used with caution since the corrections at
the longest spacings can become quite large.

\subsubsection{Miscellaneous}

\begin{description}
\myitem{SPLIT} was changed to prevent confusing messages about which
   calibrations are applied.
\myitem{CLIP} was changed to prevent an erroneous error message and to
   prevent confusing messages about calibrations.
\myitem{FILLM} was changed to first try to open the input file name as
   given by the user.  Only if that fails does it try names
   concatenating the file number.
\myitem{HOLOG} was changed to allow taper when doing the direct Fourier
   transform rather than only with a grdidded transform.  An option to
   write out an interpolated (via FFT) phase image as well as the
   interpolated amplitude image was also added.
\myitem{SHAHO} is a new task to flag holography data for shadowing.  In
   holography, one or even both antennas point at a direction other than
   the source.  In smaller configurations at longer wavelengths, this
   can be a serious issue.
\myitem{DBCON} was altered to avoid confusion from antennas in the
   antenna files labeled as {\tt OUT} or declared to be exactly at
   zero.  The EVLA always shows 28 antennas in the antenna file, one or
   more of which are called {\tt OUT}.
\end{description}

\subsection{General}

\begin{description}
\myitem{Time} axes are usually in units of days, not the seconds that
   were assumed by some portion of the code.  Plot routines were changed
   to show times in sexagesimal or in plain hours,
\myitem{UPDERROR}\hspace{2em} in the midnight job script invoked {\tt
   mail} rather than the more modern {\tt sendmail}.  This was changed
   to report errors with the same email process as in the final {\tt
     UPDREPORT}\@.
\myitem{OBIT} can now support either Python 2 or Python 3.  {\tt
   OBITVERS} was added to all ``verbs'' that invoke the OBIT package
   including {\tt BDFLIST}, {\tt BDF2AIPS}, and the four versions of
   {\tt OBIT} imaging.
\end{description}

\section{Patch Distribution for \OLDNAME}

Important bug fixes and selected improvements in \OLDNAME\ can be
downloaded via the MNJ or from the Web beginning at:
\hspace{3em}{\tt http://www.aoc.nrao.edu/aips/patch.html}\\
Alternatively one can use {\it anonymous} \ftp\ to the NRAO server
{\tt ftp.aoc.nrao.edu}.  Documentation about patches to a release is
placed on this site at {\tt pub/software/aips/}{\it release-name} and
the code is placed in suitable sub-directories below this.  As bugs in
\NEWNAME\ are found, they are simply corrected since \NEWNAME\ remains
under development.  Corrections and additions are made with a midnight
job rather than with manual patches.  Because of the many binary
installations, we now actually patch the master version of \OLDNAME,
meaning that a MNJ run on \OLDNAME\ after the patch will fetch the
corrected code and/or binaries rather than failing.  Also,
installations of \OLDNAME\ after the patch date will contain the
corrected code.  The \OLDNAME\ release has had a number of patches:
\begin{enumerate}
  \item\ {\tt SPLIT} and {\tt CLIP} would always say that is not
    calibrating anything despite the adverbs. {\it 2021-01-20}
  \item\ {\tt SPRMS} had a slight error in labeling frequency and the
     Y axis. {\it 2021-02-23}
  \item\ {\tt CLIP} generated a false error message. {\it 2021-04-14}
  \item\ {\tt VLBARUN} needed to reset {\tt IMSIZE} after {\tt UVPLT}
    calls; also allow PostScript out when {\tt convert} does not
    work. {\it 2021-04-22}
  \item\ {\tt UVPLT} could decide to plot phases from 0 to 360
     ignoring any user-specified range. {\it 2021-04-27}
  \item\ {\tt LISTR} listed single-source velocities incorrectly. {\it
      2021-04-27}
\end{enumerate}
%\vfill\eject

\section{\AIPS\ Distribution}

We are now able to log apparent MNJ accesses and downloads of the tar
balls.  We count these by unique IP address.  Since some systems
assign the same computer different IP addresses at different times,
this will be a bit of an over-estimate of actual sites/computers.
However, a single IP address is often used to provide \AIPS\ to a
number of computers, so these numbers are probably an under-estimate
of the number of computers running current versions of \AIPS\@.  So
far in \THISYEAR\ more than 295 IP addresses have downloaded the frozen
form of \OLDNAME, while more than 322 IP addresses have downloaded
\RELEASENAME\@.  A total of 685 different IP addresses have appeared in
one of our transaction log files.  These numbers are rather lower than
those of last year at this time.

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\end{document}
