An Inventory of UTC Dependencies for IRAF

TL;DR

This paper inventories and discusses the dependencies of the IRAF astronomical image processing software on Universal Time (UT), highlighting potential issues and implications for the astronomical community.

Contribution

It provides a comprehensive inventory of IRAF's dependencies on UT and analyzes their implications for astronomical data processing.

Findings

IRAF has extensive dependencies on UT throughout its codebase.

The inventory of UT dependencies is much larger than during the Y2K period.

These dependencies have significant implications for astronomical data accuracy and software maintenance.

Abstract

The Image Reduction and Analysis Facility is a scientific image processing package widely used throughout the astronomical community. IRAF has been developed and distributed by the National Optical Astronomy Observatory in Tucson, Arizona since the early 1980's. Other observatories and projects have written many dozens of layered external application packages. More than ten thousand journal articles acknowledge the use of IRAF and thousands of professional astronomers rely on it. As with many other classes of astronomical software, IRAF depends on Universal Time (UT) in many modules throughout its codebase. The author was the Y2K lead for IRAF in the late 1990's. A conservative underestimate of the initial inventory of UTC "hits" in IRAF (e.g., from search terms like "UT", "GMT" and "MJD") contains several times as many files as the corresponding Y2K ("millennium bug") inventory did in the 1990's. We will discuss dependencies of IRAF upon Coordinated Universal Time, and implications of these for the broader astronomical community.