An overview of the Gemini Infrared Multi-Object Spectrograph performance budgets

The Gemini Infrared Multi-Object Spectrograph (GIRMOS) is an upcoming Gemini instrument that will be fed by the future Gemini North Adaptive Optics (GNAO) system. A critical feature of GIRMOS is multi-object adaptive optics (MOAO), providing an additional component of correction to GNAO; this feature will not only provide exceptional science, but also act as a key demonstrator for future extremely large telescope instrumentation, which will greatly benefit from MOAO capabilities. GIRMOS houses both an Imager and Imaging Spectrograph; as such, it is capable of several observing modes that span a range of spectral resolutions, field-of-views and pixel samplings on their detectors. These observing modes enable GIRMOS to be a scientifically versatile instrument with a substantial suite of science programmes, encompassing cutting edge science that ranges from the high redshift universe down to objects within our solar system. Several notable driving science cases enable GIRMOS to provide unique and critical observations, unfeasible by any other ground-based facility while simultaneously being complementary to JWST. We present here a detailed flowdown of the GIRMOS driving science cases to individual subsystems of the instrument in the form of performance budgets. In particular, we derive subsystem requirements for both the spectrograph and imager from several key cardinal science cases. This derivation leverages an end-to-end model of the entire system, including AO-modelling, site and telescope considerations, instrument-specific characteristics such as flexure and vibration, and typical observing practices.