The software for the AAT's HERMES instrument

The High Efficiency and Resolution Multi Element Spectrograph, HERMES, was an approximately $12 million dollar project to provide a new facility class instrument for the Anglo-Australian Telescope (AAT). It was commissioned in Q4 2013. This paper examines how software challenges presented by HERMES were handled, including: minimizing cost through reusing the existing AAT 2dF/AAOmega facility software as far as possible; using instrument and data simulators to ensure new software was almost ready before any hardware had been seen; extensive upgrading of our fiber data reduction software; dealing with the tighter calibration and alignment tolerances of a high-resolution spectrograph.