The UK Astronomy Technology Centre (UKATC), Edinburgh, Scotland aims to help keep the UK at the forefront of world astronomy by providing a UK focus for the design, production and promotion of state of the art astronomical technology. The UKATC built two Calibration Units for the Gemini Observatory, one for each of the telescopes based in Hawaii and Chile. Observatory Sciences was responsible for all aspects of the production of the high-level GCAL control software, including on-site commissioning in Hawaii.