Overview of the VIRMOS instrument and data reduction software packages

VIMOS is a spectrograph with imaging capabilities which will be mounted on the Nasmyth B focus of VLT UT. The main characteristics of VIMOS are the multiplexing spectral capabilities up to spectra per exposure and the presence of an Integral Field Unit IFU which allows spectrophotometry of 1 squared arcmin field. To reach the goal of 800 spectra per field VIMOS has been designed with a large field of view divided into quadrants each quadrant being by all means a full spectrograph on its own Spectra are obtained using masks with slits which are designed by the astronomer. The ESO VLT Project has devised a general Data Flow within which all VLT instruments have to operate During design and development of VIMOS instrument software we had to deal with the VLT general concept and adapt it to our needs