<p>The two-dimensional Grid-based Energetic Neutral Atom (GENA) imager, carried by the Queqiao-2 relay communication satellite, utilizes two narrow side-by-side multi-pixel shared collimators. In this study, a new set of response functions was developed for the instrument's collimation system design to simulate measurement outcomes. The distribution of ring current ENA particles in different directions under various geomagnetic conditions was simulated. Numerical calculations and expected GENA’s measurements were obtained based on the simulation data. The results indicated the following: (1) The design of the collimation system and the dynamic range of GENA satisfy the requirements for imaging and measuring the ENA emission sources in the magnetosphere; (2) The images produced by the juxtaposed collimators exhibit no stitching artifacts. Furthermore, the field-of-view (FOV) sharing feature of the two independent collimators enhances the objectivity of the ENA differential flux evaluation; (3) The dynamic process of geomagnetic activity can be monitored through panoramic imaging of ENAs with high spatial and temporal resolution. This capability allows for accurate measurement of the spatial distribution and transmission paths of ENAs, which is crucial for distinguishing magnetic storms from substorms; (4) The substantial data collected by GENA may lead to the development of a new space weather forecasting index.</p> Graphical Abstract <p></p>