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IRAF is a collection of software written at the National Optical Astronomy Observatory (NOAO) geared towards the reduction of astronomical images and spectra in pixel array form.…
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IRAF (Image Reduction and Analysis Facility) is a collection of software written at the National Optical Astronomy Observatory (NOAO) geared towards the reduction of astronomical images and spectra in pixel array form. This is primarily data taken from imaging array detectors such as CCDs.
IRAF is a collection of software written at the National Optical Astronomy Observatory (NOAO) geared towards the reduction of astronomical images and spectra in pixel array form. This is primarily data taken from imaging array detectors such as CCDs. It is available for all major operating systems for mainframes and desktop computers. IRAF was designed cross-platform, supporting VMS and UNIX-like operating systems. Use on Microsoft Windows was made possible by Cygwin in earlier versions, and can be today done with the Windows Subsystem for Linux. Today, it is primarily used on macOS and Linux.
IRAF (Image Reduction and Analysis Facility) is a collection of software written at the National Optical Astronomy Observatory (NOAO) geared towards the reduction of astronomical images and spectra in pixel array form. This is primarily data taken from imaging array detectors such as CCDs. It is available for all major operating systems for mainframes and desktop computers. IRAF was designed cross-platform, supporting VMS and UNIX-like operating systems. Use on Microsoft Windows was made possible by Cygwin in earlier versions, and can be today done with the Windows Subsystem for Linux. Today, it is primarily used on macOS and Linux.
IRAF commands (known as tasks) are organized into package structures. Additional packages may be added to IRAF. Packages may contain other packages. There are many packages available by NOAO and external developers often focusing on a particular branch of research or facility.
Functionality available in IRAF includes the calibration of the fluxes and positions of astronomical objects within an image, compensation for sensitivity variations between detector pixels, combination of multiple images or measurement of the redshifts of absorption or emission lines in a spectrum.
While IRAF is still very popular among astronomers, institutional development and maintenance was stopped. IRAF is now maintained as community software.
The IRAF project started in fall 1981 at Kitt Peak National Observatory. In 1982, a preliminary design and the first version of the Command Language (CL) were completed. The IRAF Group was founded. Designer of the IRAF system and chief programmer was Doug Tody. In 1983, Space Telescope Science Institute selected IRAF as the environment for their SDAS data analysis system and ported the system to VMS. The first internal IRAF release was in 1984. After a limited distribution of a few outside sites the first public release was 1987.
In the middle of the 1990s, the "Open IRAF" project was started to address the problems that were seen at that time. This included language bindings, a way to use IRAF components without the full IRAF environment, new data types and dynamically loadable user code. This project was never completed.
At the end of the 1990s, the IRAF development slowed down considerably, as the system was considered mature. The user support was transferred to a Web forum in 2005 and new development of the core system was officially decreased to a very low level. However, voluntary work of the IRAF developers continued and they distributed some unofficial intermediary versions.
Source: IRAF (CC BY-SA)
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From 2006 to 2009, a first effort was made to port IRAF to 64 bit at the Institute of Space and Astronautical Science Japan. While this effort did not evolve into a new official IRAF version, it contributed significant portions to the 64-bit port by NOAO.
NOAO resumed development efforts in 2007, porting the system to 64 bit and adding Virtual Observatory capabilities to it. This phase ended in 2013 with the release of version 2.16.1.
In 2017, the source code was transferred to GitHub. In an effort to package the IRAF software for Debian, it was cleaned up from the remaining non-free source code and is maintained solely by the community since then. After a few pre-releases, version 2.17 was released in early 2022.
2023, NOIRLab (successor of NOAO) resumed some development and created their own release 2.18 with the scope limited to support the legacy Gemini data reduction pipeline. The relevant changes were later merged into the community release 2.18.
The licensing of IRAF generally follows the MIT license scheme. Older versions contained some non-free software. In particular, the NCAR graphics code restricted re-distribution of IRAF before it was removed in version 2.16. Also, old versions used code taken from the Numerical Recipes book under a different license. This code was removed or replaced with Open Source in versions after 2.16.1. This allowed the distribution of IRAF packages in mainstream Linux distributions like Debian or Ubuntu.
Four basic components make up the run-time IRAF system:
The Applications Packages are a structured collection of portable tasks for scientific data reduction and analysis, but also for system utilities.
The Command Language (CL) is the default interactive user interface and is also used as scripting language for tasks in the application packages.
The Virtual Operation System (VOS) provides a portable interface for the application tasks. It is modeled after the Unix system functions, but with an API for the IRAF specific Subset Preprocessor language (SPP).
The Host System Interface (HSI) is the kernel providing an interface between the host system and the functions of the VOS. It also provides tools necessary for bootstrapping the system from source. The SPP compiler is also part of the HSI.
Only the HSI is system dependent. All other components are portable by the use of the functions provided by the HSI. This way, porting to a new system requires only changes in this component. However, the initial design was implicitly based on the universal use of 32-bit data types and therefore the port to 64 bit required major efforts not only in the HSI but in all components of the system.
Application Packages are recursively structured in subpackages and tasks. They can be divided into two classes: general system and basic dataprocessing utilities, and packages specific to astronomical data reduction and analysis. The tasks are dominantly written in SPP and CL.
