Résumé
The JWST Mid Infrared Instrument (MIRI) operates in the 5-28 mu m wavelength range and can be configured for imaging, coronographic imaging, long-slit, low-resolution spectroscopy or medium resolution spectroscopy with an integral field unit.
SCASim is one of a suite of simulators which operate together to simulate all the different modes of the instrument. These simulators are essential for the efficient operation of MIRI; allowing more accurate planning of MIRI observations on sky or during the pre-launch testing of the instrument. The data generated by the simulators are essential for testing the data pipeline software. The simulators not only need to reproduce the behaviour of the instrument faithfully, they also need to be adaptable so that information learned about the instrument during the pre-launch testing and in-orbit commissioning can be fed back into the simulation.
SCASim simulates the behaviour of the MIRI detectors, taking into account cosmetic effects, quantum efficiency, shot noise, dark current, read noise, amplifier layout, cosmic ray hits, etc... The software has benefited from three major design choices. First, the development of a suite of MIRI simulators, rather than single simulator, has allowed MIRI simulators to be developed in parallel by different teams, with each simulator able to concentrate on one particular area. SCASim provides a facility common to all the other simulators and saves duplication of effort. Second, SCASim has a Python-based object-oriented design which makes it easier to adapt as new information about the instrument is learned during testing. Third, all simulator parameters are maintained in external files, rather than being hard coded in the software. These design choices have made SCASim highly reusable. In its present form it can be used to simulate any JWST detector, and it can be adapted for future instruments with similar, photon-counting detectors.