To:      Phyllis Jackson

From:    Eric Greisen

Date:    1 October 1993

Subject: Quarterly Report on AIPS (1993 Q3)


     The 15JUL93 release of "Classic AIPS" was made available only a
little more than a month late.  By the end of September, we had
shipped the release to 57 institutions, 19 by magnetic tape and 38 by
electronic file copies.  The improved installation procedures have
generated complements from recipients of the system.

     Many of the changes in AIPS during the last quarter were
generated by our work on the VLBA, the VLA all-sky survey, and the DDT
test package.  AIPS task FITLD is the interface to the VLBA Correlator
and continues to be upgraded to handle all of the varied outputs now
coming from the Correlator.  Testing and early data reduction for the
sky survey has led to numerous, mostly small, improvements and
corrections throughout the imaging and calibration software.  Of
particular interest is the option added to WFCLN to re-scale the
residual image after deconvolution before the components are restored.
This is needed to make the units of the residual and the components
the same.  The survey forced us to increase sharply the number of
sources allowed in an AIPS file.  It also caused us to improve and
extend two tasks originally submitted to us by Walter Jaffe (Leiden).
These are SAD, which finds, fits, and removes sources from images, and
CCNTR which plots the results.

     The DDT test is used to confirm the correctness of AIPS programs
over time and differences in computer architecture and to measure the
performance of computers.  It was revised to use CALIB for the self
calibration step rather than the obsolete ASCAL.  A very large number
of other changes were triggered by this, beginning with corrections to
the handling of rotations and shifts in imaging, particularly in  the
subtraction of source models.  Small bugs in the gridding, Fourier
transforming, and beam fitting were also corrected.  Imaging routines
were given a user-controlled parameter to limit the area of the uv
plane actually used and deconvolution routines were given a finer
histogram and a user-set parameter to control the number of pixels
searched for components in any major cycle.  These changes have
improved the speed and accuracy of the imaging and deconvolution, at
least when used correctly.  All AIPS tasks which use the pseudo array
processor now take advantage of as much of that memory as they can use
profitably with limitations which can be set at run time.

     The real-time version of FILLM has been released to allow users
to load their data into AIPS at the VLA and AOC while the observations
are proceeding.  Task IBLED now handles small amounts of data nicely,
allowing users a clearer view of the samples which need deletion.  Two
new verbs were added to manipulate history files: HITEXT writes
history to a user-selected text file and STALIN "sends lines of
history to Siberian salt mines."  The POPS language processor was
changed to allow verbs to be defined at run time and to find adverb
values symbolically rather than through lists set at compile time.
These changes mean that the users should never have to discard their
old procedures and other POPS environment to pick up new verbs and
adverbs.  POPS can now handle long string adverbs correctly.  And
tasks run in batch mode now execute at an appropriately low priority.


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