The Very Large Telescope Visible Multi-Object Spectrograph Mask Preparation Software

VIMOS ( Visible Multi- Object Spectrograph) is a multiobject imaging spectrograph installed at the VLT ( Very large Telescope) at the ESO ( European Southern Observatory) Paranal Observatory that is especially suited for survey work. VIMOS is characterized by its very high multiplexing factor: it is possible to take up to 800 spectra with 10 long slits in a single exposure. To fully exploit its multiplexing potential, we designed and implemented a dedicated software tool: the VIMOS Mask Preparation Software ( VMMPS), which allows the astronomer to select the objects to be spectroscopically observed, and provides for automatic slit positioning and slit number maximization within the instrumental constraints. The output of VMMPS is used to manufacture the slit masks to be mounted in the instrument for spectroscopic observations.