The 4MOST numerical instrument model: TOAD

The 4-metre Multi-Object Spectroscopic Telescope (4MOST) instrument uses 2436 individually positioned optical fibres to couple the light of targets into its spectrographs. TOAD, the "Top Of the Atmosphere to Detector" simulator, is a primary engineering tool that accompanies the development of the 4MOST instrument. The tool provides a detailed, end-to-end performance model both in terms of throughput and image quality for 4MOST. Its results are used for system performance analysis, data reduction pipeline development and to generate input data for other simulation tools of the project.