HRMOS: Instrument architecture and main features

The Very High-Resolution Multi-Object Spectrograph (HRMOS) will be proposed as a new instrument for the ESO VLT. HRMOS will enable groundbreaking scientific investigations that would otherwise remain inaccessible. These include the study of extrasolar planets in crowded stellar environments, testing hierarchical galaxy formation scenarios in dwarf galaxies, and providing alternative constraints on cosmological parameters through precise age determinations of the oldest stellar populations. At the same time, HRMOS will also be unique in complementing spectroscopic surveys done at lower resolution, allowing detailed investigations of young stars and their magnetic phenomena, stellar physics and nucleosynthesis, star cluster science, and interstellar medium abundance measurements. It will be an High Resolution spectrograph able to provide a resolving power of 80000 in three spectral window of approx. 140nm each. It will have Multiplexing capabilities in the range of 50 to 80 and will be carchterized by a radial velocity precision of 10m/s. In this paper we will present the instrument architecture detailing the main technical carachteristics. The instrument front end that will pick up the stars and correct the atmospheric dispersion, the fiber link that will bring the light to the spectrogrpah by providing slicing and scrambling features and the spectrograph concept will be described in this paper