%-----------------------------------------------------------------------
%;  Copyright (C) 2026
%;  Associated Universities, Inc. Washington DC, USA.
%;
%;  This program is free software; you can redistribute it and/or
%;  modify it under the terms of the GNU General Public License as
%;  published by the Free Software Foundation; either version 2 of
%;  the License, or (at your option) any later version.
%;
%;  This program is distributed in the hope that it will be useful,
%;  but WITHOUT ANY WARRANTY; without even the implied warranty of
%;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%;  GNU General Public License for more details.
%;
%;  You should have received a copy of the GNU General Public
%;  License along with this program; if not, write to the Free
%;  Software Foundation, Inc., 675 Massachusetts Ave, Cambridge,
%;  MA 02139, USA.
%;
%;  Correspondence concerning AIPS should be addressed as follows:
%;          Internet email: aipsmail@nrao.edu.
%;          Postal address: AIPS Project Office
%;                          National Radio Astronomy Observatory
%;                          520 Edgemont Road
%;                          Charlottesville, VA 22903-2475 USA
%-----------------------------------------------------------------------
%Body of intermediate AIPSletter for 30 June 2026 version

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

\newcommand{\AIPRELEASE}{June 30, 2026}
\newcommand{\AIPVOLUME}{Volume XLVI}
\newcommand{\AIPNUMBER}{Number 1}
\newcommand{\RELEASENAME}{{\tt 31DEC26}}
\newcommand{\NEWNAME}{{\tt 31DEC26}}
\newcommand{\OLDNAME}{{\tt 31DEC25}}
\newcommand{\THISYEAR}{2026}
\newcommand{\NEWYEAR}{2026}
\newcommand{\OLDYEAR}{2025}
\newcommand{\putfig}[1]{\includegraphics{#1.eps}}

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

\newcommand{\MYSpace}{-11pt}

\normalstyle

\section{Happy 47$^{\rm th}$ birthday \AIPS\ and FITS}

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
the 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.  The FITS format then 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.

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 {\tt
  daip@nrao.edu}.  Do note that the \AIPS\ web site has become a secure
({\tt https:}) web site.

\section{R.I.P.}

We are saddened to report that Tony Willis, our friend and colleague,
died at the end of 2025.  He was instrumental in getting the {\tt ALBUS}
software to its present state.  It is the best ionospheric TEC and
rotation measure software according to our studies.  Future development
of {\tt ALBUS} is now problematical.

On a less serious note, the computer used to create the {\tt MACINT}
binary version of \AIPS\ died in January.  This means that there is no
\NEWNAME\ binary version for {\tt MACINT} and that the \OLDNAME\
{\tt MACINT} binary version has not been updated for most of the
``patches'' listed later in this \Aipsletter.  Do remember that all
operating systems can still compile \AIPS\ locally using {\tt gfortran}
and {\tt gcc}.  The computer used to create the \NEWNAME\ binary version
for Apple Mac computers with the M1 through M5 cpu chips will have to
have its operating system updated later this year.  We hope that that
will not have any bad consequences.  At that time the \OLDNAME\ release
will be frozen with no more bug fixes so that that version will not be
affected.

\section{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
(64-bit only), and MacIntosh OS/X (ARM only) systems may install
binary versions of recent releases.  The last ``slushy'' release is
called \OLDNAME\@.  It gets occasional bug fixes until changes in
operating system versions force it to be frozen.  \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
(``source'') installations, the Unix tool {\tt cvs} running with
anonymous ftp was used for the MNJ\@.  That has been replaced with
{\tt rsync} to download any changed text files.  The only installations
to still use {\tt cvs} are the four machines inside the Socorro Array
Operations Center.  Do not modify \AIPS\ text files (\eg\ Fortran tasks)
in the standard locations since {\tt rsync} will over-write them.  For
local versions, use a copy of the task and its help file in a private
disk area instead.

{\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.  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 development release.

\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}.

We have discontinued paper copies of the \Aipsletter\ entirely.  The
\Aipsletter\ will be available in PostScript and pdf forms as always
from the web site listed above.  New issues will be announced on the
bananas and MNJ list server.  Readers are encouraged to subscribe to one
of these low volume mail lists at {\tt
  htps://listmgr.nrao.edu/mailman/listinfo}.

\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 are
three new user tasks and 1 new verb already in \RELEASENAME\@.  The new
tasks include {\tt SPLOT} to plot various table parameters with each
page devoted to all antennas for one parameter, IF, and polarization or
all IFs for one antenna and polarization.  New task {\tt TUVCP} copies
a multi-subarray data set correcting times of each subarray and task
{\tt POLTS} is used to study the biases in measurement of total
polarization.  The new verb {\tt VGLIST} provides information on
available {\tt VGET} tasks.

\subsection{Display}

The tasks which generate plots with time as the horizontal axis were
revised to offer the option to plot the time in only a semi-linear
fashion with gaps in the data closed up.  This is similar to the time
axes in {\tt TVFLG} and {\tt SPFLG}\@.  Multiple options are offered to
control how the tic marks in gaps are labeled.  Tasks that support this
option are {\tt TEPLT}, {\tt SNPLT}, {\tt VPLOT}, {\tt WETHR}, {\tt
  SNBLP}, {\tt BPPLT}, {\tt ANBPL}, and the new {\tt SPLOT}\@.  These
tasks also received minor corrections and changes to the coloring
option.  In particular, {\tt VPLOT} can now color by source instead of
by IF\@.

{\tt BPLOT} was given the option of plotting a labeled color wedge on
the right hand side of the plot.  The antennas are now displayed in the
order specified by the {\tt ANTENNAS} adverb, allowing the user to
juxtapose related antennas rather than on simple numerical order.  The
new task {\tt SPLOT} is similar to {\tt BPLOT} but plots all the
parameters supported by {\tt SNPLT} from {\tt SN}, {\tt CL}, {\tt TY},
{\tt SY}, and {\tt PC} tables.  Each page of the plot shows 1 IF and
polarization for a list of antennas or 1 antenna and polarization for a
sequence of IFs.  The antennas or IFs are separated by an interval
vertically.  The plots can be colored by the parameter values or by the
vertical sequence.  Examples are shown on the last real page of this
\Aipsletter.
%\vfill
\eject

Several plot tasks were changed to allow the user to choose how the
plots are done.  The choices are (1) direct lines between the data
points, (2) a step function with flat tops through the data points
rising half-way between the data points, and (3) the step function
with lines to the plot minimum half way between the data points.
{\tt GREYS} and {\tt PRPLT} offer this choice for plots of the
``profile'' averaged along 2 axes of the image cube and plotted along
the third.  {\tt ISPEC}, {\tt RSPEC}, and {\tt IMEAN} were provided
similar options.

\begin{description}
  \myitem{LISUN} now offers the printer plot of VLA antenna locations
     from {\tt PRTAN} and the integration time like {\tt GETITIME}\@.
  \myitem{IMAGR} TV display was corrected to label the step wedge with
     the current display range and to show spectral channel number and
     facet number but only when relevant.
  \myitem{PRTAN} can plot the antenna locations on a simple linear scale
     or, for VLBI, on a partial or full globe in an Aitoff projection.
     The printing can now be suppressed and now only requires one call
     to {\tt GETANT} rather than reading the {\tt AN} table multiple
     times.
  \myitem{TVMENU} subroutine used by most interactive tasks was changed
     to enlarge the TV display if allowed and needed to hold the task's
     menus.  When this is not allowed, better error messages are now
     generated.
  \myitem{PLOTR} added {\tt PIXRANGE} to control the vertical plot
     range and changed 2 {\tt APARM}s to control the horizontal range
     used in fitting the data.
  \myitem{LWPLA} was enhanced to allow {\tt evince} to be used as the
     ``preview printer'' since it can handle pdf, PostScript, and text
     files and ghostview is now not present on some computers.
  \myitem{TVDATA} and {\tt TVFACTS} verbs now display the number of
     pixels on each side of the display in addition to the corner
     coordinates.
\end{description}

\subsection{Spectral analysis}

The spectral fitting tasks {\tt XGAUS} (Gaussian fitting), {\tt ZEMAN}
(Zeeman splitting), {\tt RMFIT} (Rotation measure fitting), {\tt AGAUS}
(Gaussian fitting in absorption), and {\tt ZAMAN} (Zeeman fitting in
absorption) were substantially revised in the last few months.  All of
these tasks were changed to compute the spectral rms when initially
reading the data cubes and then revise it at each pixel for which a fit
is attempted.  The rms image(s) can be displayed and used in the edit
stage and written out when exiting under control of {\tt DOOUTPUT}\@.
The right-hand portion of the edit menu was changed to check the display
height and then offer all {\tt SHOW IMAGE }{\it xxxn} options for the
number of components that will fit while showing the remaining
components as {\tt CHOOSE COMP }{\it n} options.  Selecting one of the
latter changes which components are available with the full {\tt SHOW
  IMAGE }{\it xxxn} options.  The option(s) to show the rms image(s) and,
in {\tt RMFIT}, the gain always appear.  On writing output images, all
these tasks now copy the large {\tt XG}, {\tt ZE}, or {\tt RM} tables
only to the residual image cubes.  All potential output images are
written when they contain at least one valid pixel, fully blanked images
are deleted.  All output images are marked as magic-value blanked if
appropriate.

{\tt XGAUS} was given the option to display spectra on a non-linear
intensity axis with log10, square root, and cube root plotting.  The
log10 is problematical since negative intensities cannot be displayed.
The other two take the square or cube root of the absolute value and
then restore the initial sign to the result.  The non-linear plots
are useful when the dynamic range of the spectrum is large, \ie\ in
maser fields.  The user may switch the choice of linear and the
non-linear form from menu options and also with TV button D while
setting the initial guess.  {\tt AGAUS} has a similar non-linear option
but only while setting initial guesses on spectral plots of optical
depth.  The non-linear options are not available (or useful) when
plotting absorption, Zeeman, and rotation measure spectra.  {\tt RMFIT}
now displays the residual rms on plots of Q and U rms.

\AIPS\ memos 118 and 122 were revised to explain the new options and
to show the new and revised displays.  Task {\tt XG2PL} was corrected
to handle the maximum number of components (now 32) and other table
format changes.  The print portion also required changes to formats and
to data scaling.

\subsection{UV data}

The scheme by which {\tt EDITA}, {\tt EDITR}, and, {\tt SNEDT} extend
any time range received attention.  Adverb {\tt EXTIME} was added to
limit the size of these time extensions and to determine whether the
time interval backwards and forwards is based on the times only of the
current antenna or of all antennas.  The dummy times added at the start
and end times and any time gaps were changed to scale by {\tt DETIME}
rather than {\tt SOLINT} which is usually much smaller.  The ``expert''
mode available in these tasks was deleted.  It was hard to use and is no
longer needed on modern, much faster computers.

Because total polarization and visibility amplitude are computed with the
square root of a sum of squares, they are fundamentally positive even
when the Q, U, real, and imaginary contain only noise with zero mean.
To test the correction for polarization in {\tt COMB} and {\tt POLCO} a
new task {\tt POLTS} was written.  It generates one million random
numbers with \AIPS\ random number generator.  Then it loops over numerous
signal-to-noise ratios and the million random numbers to determine the
mean and median measured ``polarization''.  The results are written into
a text file in the {\tt PLOTR} format.  That task was then used to
determine a best fit polynomial and a new subroutine was written to
use the polynomial to correct the measurements.  After a few iterations,
the routine converged as well as it could.  That new subroutine was
added to {\tt COMB} and {\tt POLCO}.  The good news is that all of them
work rather well with an error of about 0.004 sigma for the original
routines in {\tt COMB} and {\tt POLCO} and a bit less (0.001 sigma) for
the new routine.  The Ricean bias (error) gets rather larger for S/N
less than 5.

{\tt TECOR} and {\tt ALBUS} were changed to define each entry in the
{\tt TE} table as applying to all antennas or to a specific antenna.
This greatly reduces the size of the {\tt TE} table for the VLA but
allows the user to request separate values for each antenna.  This may
be appropriate for the VLA in A configuration.  These tasks had a number
of minor corrections and {\tt TEPLT} and {\tt RIFRM} were adjusted to
handle the new table format.

\begin{description}
  \myitem{CLCOR} was corrected to examine the {\tt CT} table and apply
      the default handling for all dates zero only when they are all
      zero.  The five day numbers in {\tt CT} tables can start with 0,
      -1, and even -2.
  \myitem{RLDIF} had Rick Perley's functions for 3C286 and 3C138 changed
      with a new fit and an option to print all ``expected'' values used
      was added.
  \myitem{FITLD} was changed to accept the new 16- and 256-level data
      which will appear with the VNDA enhancement of the VLBA\@.  The
      option to scale the visibilities but not to do the FFT correction
      on auto-correlation data was added.
  \myitem{TUVCP} is a new task which copies a data set adding a separate
     user-specified time to each subarray.  Multiple subarray data sets
     that have passed through CASA may require this,
\end{description}

\subsection{General}

\begin{description}
  \myitem{VGLIST} is a new verb which lists how many tasks are available
     for {\tt VGET} under each of the 35 possible {\tt VNUMBER}s.
  \myitem{CookBook} and other documentation was updated in February.
  \myitem{AIPS} code was revised to eliminate warnings from {\tt gcc}
     and {\tt gfortran}.  In particular, an incorrect usage of common
     ({\tt external} in {\tt gcc}) in the \AIPS\ TV ({\tt XAS.SHR})
     code was corrected and an option was added to the {\tt Makefile}
     for new compilers which make {\tt -fno-common} the default.
  \myitem{Ecliptic} longitude and latitude are no longer included in
     the list of supported coordinate types and are simply replaced
     by longitude ({\tt LONG})  and latitude ({\tt LATI}) with no
     adjective.
  \myitem{TRANS} was changed to avoid copying Clean Component ({\tt CC})
     and Model Fit ({\tt MF}) tables.  They can be quite numerous and
     are not useful on the transposed image cube.
  \myitem{SUBIM} was changed to handle old image headers that have zeros
     for the size of some of the 7 axes.  It was given adverb {\tt
       DCODE} to suppress copying of {\tt CC} and/or {\tt MF} tables
     optionally.
  \myitem{PATGN} was given the option to add noise to the pattern images
     it generates and had an elliptical Gaussian pattern added.
\end{description}

\section{Patch Distribution for \OLDNAME}

This section lists the patches that have been released for \OLDNAME\@.
The ``Midnight Job'' ({\tt \$HOME/do\_daily.}{\it hostname}) will
update your locally-compiled and binary installations.  Major bug
corrections are moved to \OLDNAME\ as they occur and users should use
the MNJ on occasion on both the {\tt NEW} and {\tt TST} versions of
\AIPS\@. The \OLDNAME\ release has had a number of these ``patches'':

\begin{enumerate}
  \item\ {\tt ALBUS} did not read all of its adverbs. {\it 2026-01-14}
  \item\ {\tt KNTR} read an extra plane when the Clean beam was plotted
      in a separate panel. {\it 2026-01-16}
  \item\ {\tt VLBARUN} and {\tt VLBAPIPE} tried to write to a directory
      not properly created when {\tt OUTFILE} was blank. {\it
        2026-01-20}
  \item\ {\tt TABED} wrote confusing summary messages. {\it 2026-02-03}
  \item\ {\tt RLDLY} did not handle {\tt REFANT=0} well when {\tt
      DETIME} was 0. {\it 2026-02-06}
  \item\ {\tt VLBARUN} and {\tt VLBAPIPE} had hard failure caused by the
      patch listed above. {\it 2026-02-13}
  \item\ {\tt \$APLUNIX/ZTKOP2.C} and {\tt \$APLLNX64/ZTQSP2.C} had
      missing includes required by modern systems. {\it 2026-02-19}
  \item\ {\tt XAS.SHR} did not define {\tt XLink} as {\tt int} and
      assumed that commons were okay by default. {\it 2026-02-19}
  \item\ {\tt FTFLG} did not handle short rows in expanded displays when
      flagging. {\it 2026-03-25}
  \item\ {\tt PRPLT} had small errors in plotting coordinates corrected
      and new plot types added with control of data outside the user's
      {\tt PIXRANGE}\@. {\it 2026-04-29}
  \item\ {\tt IMAGR} mis-labeled the step wedge. {\it 2026-05-18}
  \item\ {\tt IMHEAD} needed changes in formats. {\it 2026-05-21}
  \item\ {\tt TRANS} copied {\tt CC} and {\tt MF} tables uselessly. {\it
      2026-05-21}
  \item\ {\tt ZLASCL} and {\tt PRDEVS.LIST} were changed to add {\tt
      evince} as a possible preview ``printer''.  Added explain to {\tt
      PRINTER} help file. {\it 2026-05-27}
  \item\ {\tt XGAUS}, {\tt AGAUS}, {\tt ZEMAN}, {\tt ZAMAN}, and {\tt
      RMFIT} were changed to only copy the {\tt XG} or {\tt ZE} or {\tt
      RM} large tables to the output residual cube.  Changed them also
      to mark output images as blanked when needed.  Also changed them
      to write output images of any size if there are any valid pixels.
      {\it 2026-05-28}
  \item\ {\tt SPLIT} and {\tt SPLAT} tried to extract frequency offsets
      from a {\tt CL} table without making sure there was one.
      {\it 2026-06-24}
\end{enumerate}

\section{Recent Memoranda}

Most \AIPS\ Memoranda are available from the \AIPS\ home page and
essentially all are available from the NRAO Library ({\tt
  https://library.nrao.edu/aips.shtml}).  Memo 118 and 122 were
substantially revised to describe and display the new capabilities
described above.  A related VLBA Memo has also appeared and is available
from the NRAO Library ({\tt https://library.nrao.edu/vlbas.shtml}).

\begin{tabular}{lp{5.8in}}
{\bf 118} & {\bf Modeling Spectral Cubes in \AIPS}\\
   &  Eric W. Greisen, NRAO\\
   &  June 2026 revision, describing {\tt XGAUS}, {\tt ZEMAN}, and
      {\tt RMFIT}
\end{tabular}

\begin{tabular}{lp{5.8in}}
{\bf 122} & {\bf Modeling Absorption-line Cubes in \AIPS}\\
   &  Eric W. Greisen, NRAO\\
   &  June 2026 revision, describing {\tt AGAUS} and {\tt ZAMAN}
\end{tabular}

\begin{tabular}{lp{5.8in}}
{\bf 43} & {\bf VLBA Scientific Memo: On scaling of VLBA data}\\
   &  Eric W. Greisen, NRAO\\
   &  April 27, 2026\\
   &  Issues with the FITS-IDI data file and the scaling of visibility
      data by {\tt FITLD} are discussed.  Changes to {\tt FITLD} are
      described and potential calibration issues are also mentioned.
\end{tabular}

%\vfill\eject

\section{Recent Y2K tests}

We have run the Y2K test on an Apple  Mac mini with an M4 cpu.  It
achieved an \AMark\ of 1818 by executing the full test in 22 seconds
with correct results.  That has now been eclipsed by an Apple laptop
with large solid-state disk and an M5 cpu.  That machine ran the Y2K
test with correct results in 20 seconds, an \AMark\ of 2000!

\section{\AIPS\ Distribution}

We log apparent MNJ accesses and downloads of the tar balls and binary
installations.  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 may be an under-estimate of the
number of computers running current versions of \AIPS\@.  So far in
\THISYEAR\ more than 153 IP addresses have downloaded the now slushy
form of \OLDNAME, while more than 210 IP addresses have downloaded
\RELEASENAME\@.  A total of 314 different IP addresses have appeared in
one of our transaction log files.  These numbers are rather close to
those of last year at this time except those for {\tt NEW} which are 12
weeks ahead of last year.

\vspace{1em}
\centerline{\resizebox{!}{4.9in}{\includegraphics{FIG/Plot2526a.eps}}}

\vfill\eject

\vfill
\centerline{\resizebox{7.0in}{!}{\putfig{FIG/SPLOT.ant}}}
\vspace{0.2in}
\centerline{{\tt SPLOT} sample plots. {\tt OPCODE = 'ANT'; DO3COLOR = 1}
  to color by sequence.}
\vspace{0.2in}
\centerline{\resizebox{7.0in}{!}{\putfig{FIG/SPLOT.if}}}
\vspace{0.2in}
\centerline{{\tt SPLOT} sample plots. {\tt OPCODE = 'IF'; DO3COLOR = 2}
  to color by intensity.}

\vfill\eject

\vfill\eject
% mailer page
% \cleardoublepage
\pagestyle{empty}
 \vbox to 4.4in{
  \vspace{12pt}
%  \vfill
\centerline{\resizebox{!}{3.2in}{\includegraphics{FIG/Mandrill.eps}}}
%  \centerline{\rotatebox{-90}{\resizebox{!}{3.5in}{%
%  \includegraphics{FIG/Mandrill.color.plt}}}}
  \vspace{12pt}
  \centerline{{\huge \tt \AIPRELEASE}}
  \vspace{12pt}
  \vfill}
\phantom{...}
\centerline{\resizebox{!}{!}{\includegraphics{FIG/AIPSLETS.PS}}}

\end{document}
