AIPS++

Lore & Background

In 1988-89, NRAO Director Paul Vanden Bout convened the Software Advisory Group (SWAG), chaired by Tim Cornwell, with members including Geoff Croes, Gareth Hunt, Jan Noordam, and Ray Norris. SWAG recommended that all NRAO data processing be coordinated by a new Assistant Director for Computing, that AIPS be redesigned and reimplemented, and that equal attention be given to single-dish software. The NRAO Director accepted these recommendations in late 1990, and the task of defining the new package began. The project was originally a consortium effort involving the Australia Telescope National Facility (ATNF), Jodrell Bank Observatory and the MERLIN/VLBI National Facility, the Berkeley-Illinois-Maryland Association (BIMA), the National Radio Astronomy Observatory (NRAO), and the Netherlands Foundation for Research in Astronomy (ASTRON).

AIPS++ provides facilities for calibration, editing, image formation, image enhancement, and analysis of images and other astronomical data. A major focus is on reduction of data from both single-dish and aperture synthesis radio telescopes. Although the tools are mainly designed for radio telescopes, the package is expected to be useful for other astronomical data, though reduction of most imaging array detector data is performed using IRAF. AIPS++ is structured as a library of tools at lower levels, designed to replace AIPS's more monolithic applications. The counterpart of an AIPS task is an AIPS++ tool function, and AIPS adverbs correspond to parameters of AIPS++ tool functions. The command-line interpreter in AIPS is POPS; in AIPS++ it is Glish. The code standard in most astronomical institutes remains AIPS, as AIPS++ was usually not yet considered sufficiently reliable and usable. Like most research astronomy software, it is available for all major operating systems except Microsoft Windows.

On August 25, 2004, the AIPS++ code base was reorganized to a more modular structure and renamed CASA. CASA consists of C++ libraries derived from original AIPS++ tasks. The Glish scripting system is being replaced by Python bindings (CASApy). CASA is no longer developed by the consortium but mainly within NRAO for use on ALMA. The core libraries, now called CasaCore, are still maintained by original consortium members. A separate Python interface, python-casacore (formerly Pyrap), is mainly developed within ATNF and ASTRON for the Australia Telescope Compact Array, WSRT, and LOFAR. CASA uses these core libraries but not python-casacore.

Reader's Guide

AIPS++ is notable as the direct predecessor of CASA, which now underpins image processing for major next-generation radio telescopes such as ALMA, eVLA, and ASKAP. Its development was a consortium effort involving multiple astronomical institutes, reflecting a collaborative approach to replacing the aging AIPS software. The package introduced a toolkit structure of fine-grained tool functions, replacing AIPS's monolithic tasks, and used Glish as its command-line interpreter. Although AIPS remained the standard in most institutes due to reliability concerns, AIPS++ laid the groundwork for modern radio astronomy data reduction. Its legacy continues through CASA, which reorganized the code base in 2004 and is now primarily developed by NRAO for ALMA. The core libraries, CasaCore, are still maintained by the original consortium, and separate Python interfaces (python-casacore) serve other telescopes. Thus, AIPS++ represents a transitional but foundational software system in radio astronomy.

Did You Know?

• AIPS++ was written almost entirely in C++ and its development started in the early 1990s.
• The Software Advisory Group (SWAG) that recommended its creation was chaired by Tim Cornwell.
• AIPS++ was reborn as CASA on August 25, 2004, after a code reorganization.