E-ELT observations simulator

Monday 7 December 2015, by Damien Gratadour

The websim-compass observations simulator consists in a web interface coupled to an IDL code, which allows the user to perform full simulations of all E-ELT instruments foreseen for the future 39m European Extremely Large Telescope.

The web interface offers two modes. In the astronomer mode, the user is guided through the simulation parameter space along a science-oriented path that starts from choosing an instrument concept (i.e., MICADO, HARMONI or MOSAIC) and then goes into the details of the site/atmosphere, instrument setup and detector properties, for which the most technical parameters are frozen to typical/expected values. This mode is intended to help instrument consortia in assessing the instrument concepts performances relative to their prominent science cases. In the expert mode, the user rather starts from a given observational capability (i.e., imaging, IFU spectroscopy, ...), with complete freedom in term of telescope/instrument/site parameter. This mode is designed for project/instrument scientists to assist them in exploring the impact of different instrument concepts. It is also very well suited in exploring the impact of different top level requirements and help science vs. technical trade-offs during instrument conceptual studies.For both modes, two large PSF and source template databases are offered to include the effects of Adaptive Optics system and the detailed spatial/spectral properties of the astrophysical targets.

The simulation parameters are then sent to the IDL code which procudes FITS files that mimick the result of real observations. This code builds a high resolution scientific image template and add to each pixel a high resolution spectral template. These templates are constructed from observations of local objects or from results of numerical simulations. The second step consists in convolving each spectral and spatial pixel of the high resolution data cube with a PSF, which is representative of the optical path through the atmosphere and the telescope. This PSF, which captures the performances of the telescope, instrument and/or AO system, is simulated using a dedicated pipeline. In the third step, the spatial sampling of the datacube is reduced to match that of the simulated instrument. Finally, realistic sky as well as photon and detector noises are added. The simulation pipeline is science-oriented, which means that it does not perform full simulations of the instrument focal plane simulations nor does it take into account the effects due to the data reduction process. The final datacube produced can be viewed as a final product of a given data reduction software, which has perfectly extracted/reduced the data with no systematic error. This code is an evolution of previous developement of the WEBSIM tool, for which details can be found in Puech et al. 2010.

This tools are offered freely to the cummonity after an automatic registration procedure with login and password. The web human interface provides public/shared PSFs and scientific templates but also a private area in which the user can store his/her own data and manage simulations, including launching several simulations processes that are automaticaly added to a queue and executed depending of available ressources. A large multi-CPU machine is entirely dedicated to receive the simulation processes.